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Buick - Regal - Owners Manual - 1996 - 1996
Buick - Enclave - Owners Manual - 2016 - 2016
2001-2005--Buick--Century--6 Cylinders J 3.1L FI OHV--32624201
2001-2005--Buick--Rendezvous AWD--6 Cylinders E 3.4L MFI OHV--32909702
1982-1996--Buick--Century--6 Cylinders N 3.3L MFI OHV--31030403
1997-2000--Buick--Century--6 Cylinders M 3.1L FI OHV--32310301
Buick - Park Avenue - Repair Guide - (1997)
1988-1996--Buick--Regal--6 Cylinders L 3.8L FI OHV--31892402
1997-2000--Buick--Regal--6 Cylinders K 3.8L FI OHV--32570101
1992--Buick--Roadmaster--8 Cylinders P 5.7L MFI OHV--31953601
2006--Buick--Terraza 2WD--6 Cylinders 1 3.9L MFI OHV--33024502
1997-1999--Buick--Park Avenue--6 Cylinders K 3.8L FI OHV--32380301
Buick - Riviera - Owners Manual - 1997 - 1997
1988-1996--Buick--Regal--6 Cylinders M 3.1L FI OHV--32138201
2001-2005--Buick--Regal--6 Cylinders 1 3.8L FI SC OHV--32624402
Buick - Rendezvous - Owners Manual - 2003 - 2003
2006-2007--Buick--Rendezvous 2WD--6 Cylinders L 3.5L FI OHV--33023203
Buick - Century - Owners Manual - 1998 - 1998
1997-2000--Buick--Regal--6 Cylinders 1 3.8L FI SC OHV--32570102
Buick Buick Regal 2011 Buick Regal Owners Manual
Buick Lucerne Workshop Manual (V6-3.8L VIN 2 (2006))
1982-1996--Buick--Century--6 Cylinders N 3.3L MFI OHV--31892102
Buick - Riviera - Owners Manual - 1995 - 1995
Buick - Century - Owners Manual - 1993 - 1993
Buick - Regal - Owners Manual - 1998 - 1998
Buick - Roadmaster - Owners Manual - 1996 - 1996
2001-2005--Buick--Regal--6 Cylinders K 3.8L FI OHV--32910202
Buick - Skylark - Owners Manual - 1995 - 1995
Buick - Century - Owners Manual - 2001 - 2005
2001-2005--Buick--Rendezvous AWD--6 Cylinders E 3.4L MFI OHV--32670701
Buick Buick Regal 2001 Buick Regal Owners Manual
Buick - Riviera - Owners Manual - 1998 - 1998
1988-1996--Buick--Regal--6 Cylinders W 2.8L MFI OHV--31031001
Buick - Riviera - Wiring Diagram - 1986 - 1989
Buick Buick Regal 1997 Buick Regal Owners Manual
Buick - Enclave - Owners manual - 2010 - 2011
Buick - Regal - Owners Manual - 1999 - 1999
Buick Buick Rendezvous 2002 Buick Rendezvous Owners Manual
Buick Buick Century 2001 Buick Century Owners Manual
Buick Buick Riviera Buick Riviera 1967 Misc Documents Brochure
1982-1996--Buick--Century--6 Cylinders W 2.8L MFI OHV--31030402
Buick Buick Regal Buick Regal 2015 Owners Manual
2006-2007--Buick--Rainier 2WD--6 Cylinders S 4.2L MFI DOHC--33026701
Buick Buick Regal Buick Regal 2011 Misc Documents Brochure
Buick Buick Century Buick Century 1974 Misc Documents Brochure
Buick Buick Century 1996 Buick Century Owners Manual
1988-1996--Buick--Regal--6 Cylinders W 2.8L MFI OHV--31060501
Buick - Century - Owners Manual - 2000 - 2000
Buick Century Workshop Manual (L4-151 2.5L (1989))
Buick Buick Skylark Buick Skylark 1963 Misc Documents Brochure
Buick Buick Century 2002 Buick Century Owners Manual
Buick Buick Regal Buick Regal 1957 1960 Misc Documents Wiring Diagrams
1982-1994--Buick--Skyhawk--4 Cylinders M 2.0L MFI Turbo SOHC--31090902
1982-1996--Buick--Century Estate Wagon--6 Cylinders E 3.0L 2BL OHV--31673602
Buick - Regal - Owners Manual - 2015 - 2015
1982-1996--Buick--Century Estate Wagon--6 Cylinders 3 3.8L MFI OHV--31673603
Buick Buick Enclave Buick Enclave 2008 Misc Documents Brochure
Buick Buick Enclave 2009 Buick Enclave Owners Manual
2000-2005--Buick--Lesabre--6 Cylinders K 3.8L FI OHV--32966501
1990-1993--Buick--Park Avenue--6 Cylinders L 3.8L FI OHV--31750601
Summary of Content
Routine Maintenance GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Automatic Transmission Identification See Figures 1 and 2 Print All Buick, Oldsmobile and Pontiac models covered in this guide use various GM Turbo Hydra-Matic (THM) automatic transmissions. Transmission identification numbers are found on either side of the transmission case, depending on model. Some models also have I.D. numbers stamped on the governor cover. Fig. Fig. 1: Transmission I.D. location. The 375B unit is the same as the 350, except for a longer output shaft and extension housing. Fig. Fig. 2: Turbo Hydra-matic 200-4R identification location-late model. Buick models are equipped with the 200, 200C, 200-4R, 350, 375B and 400 transmissions. Oldsmobile uses the 200, 200C, 200-4R, 250, 350, 375B and 400 units, and Pontiacs are equipped with the 200, 200C, 200-4R, 350, and 400 transmissions. The 375B transmission was last used in 1976, while the 200-4R was introduced in 1981. A quick way to visually identify the transmissions is to look at the shapes of the pans. The 250, 350 and 375B have a squarish pan with the right rear corner cut off. The 200 pan is similar but more rectangular. The pan of the 400 model transmission is irregularly shaped. The 200, 250, 350 and 375B models are also identified by their kickdown linkage, which is actuated by a cable attached to the accelerator pedal linkage. The 400 model transmission has an electric kickdown connected to a switch on the accelerator linkage. The 200 model transmission was first used in 1977 and is the first all metric unit built by GM in the U.S. This transmission sometimes has the word METRIC stamped on the pan. The 200-4R model is an automatic overdrive version of the 200 transmission. The 200C, 250C and 350C transmissions are similar to those given these number designations without the C except that they incorporate a lockup clutch in the torque converter. There is little visual difference between the 350 and 375B transmissions, except that the latter has a longer output shaft and extension housing. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Drive Axle Identification See Figure 1 The drive axle identification is stamped on the forward portion of the housing or on a tag bolted to the rear cover. Print Fig. Fig. 1: Drive axle identification. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Engine See Figures 1, 2, 3, 4 and 5 Print Engine identification can take place using various methods. The VIN, described earlier in this section, contains a code indentifying the engine originally installed in the vehicle. In most cases, this should be sufficient for determining the engine with which your car is currently equipped. However, some older vehicles may have had the engine replaced or changed by a previous owner. In this case, the engine can be identified by an engine serial number stamped on the block or located on adhesive labels that may be present on the valve covers. Fig. Fig. 1: Engine number locations, engine VIN F,P,N,R,Y and K. 1975-77 Olds and Pontiac number stamped on oil filler tube. Fig. Fig. 2: Engine VIN location, late model Olds 231 V-6. Fig. Fig. 3: Early V-6 engine number location, 1977 shown. Fig. Fig. 4: VIN location, 5.0L Olds 307 CID (VIN Y) Fig. Fig. 5: Engine VIN locations, 265, 301, 305, and 350 (L-code) V-8s Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Vehicle See Figures 1, 2, 3, 4, 5, 6 and 7 Print The Vehicle Identification Number (VIN) is important for ordering parts and for servicing. The VIN is a thirteen digit (1975-1980) or seventeen digit (1981 and later) sequence of numbers and letters visible on a plate fastened to the upper left instrument panel area, seen through the windshield. Model years appear in the VIN as the last digit of each particular year (6 is 1976, 8 is 1978,etc.), until 1980 (which is A). This is the final year under the thirteen digit code. The seventeen digit VIN begins with 1981 (B), and continues 1982 (C) and so on, except letters which may be confused with numbers (I, O or Q are skipped). Because of this, 1987 is represented by (H) while 1988 is (J) and 1989 is (K). Fig. Fig. 1: Thirteen digit VIN, 1975-1980 Fig. Fig. 2: Seventeen digit VIN, 1981 and later. Fig. Fig. 3: VIN plate location. Fig. Fig. 4: The body identification plate can be used to determine the original paint and trim combinations. U.S. models is shown here. Fig. Fig. 5: Body number plate-Canadian models Fig. Fig. 6: Close-up view of the VIN plate Fig. Fig. 7: These labels are located on the inside of the drivers door and provide the date of manufacture and other information Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Vehicle Emission Control Information Label See Figures 1 and 2 Print The Vehicle Emission Control Information (VECI) label is located in the engine compartment (fan shroud, radiator support, hood underside, etc.) of every vehicle produced by General Motors. The label contains important emission specifications and setting procedures, as well as a vacuum hose schematic with various emissions components identified. When servicing your Buick, Oldsmobile or Pontiac, this label should always be checked for up-to-date information pertaining specifically to your vehicle. Always follow the timing procedures on this label when adjusting ignition timing. Fig. Fig. 1: General Motors emissions decal, 1979 231 V6 shown. Fig. Fig. 2: Emissions label location Back to Top Engine Electrical GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Adjustments All Buick, Olds and Pontiac models covered in this guide are equipped with electronic ignition systems using the HEI (High Energy Ignition) distributors. Dwell angle is permanently set on these units, requiring no adjustment or checking. There are no ignition points or other electromechanical parts to service. Print Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Component Replacement INTERNAL IGNITION COIL Print See Figures 1, 2 and 3 Fig. Fig. 1: To gain access to the internal coil, first disconnect the feed and module wires. Note: Spark plug wires were removed for illustration purposes only, this will be unnecessary during actual service Fig. Fig. 2: Removing the coil attaching screws Fig. Fig. 3: Remove the coil cover from the distributor cap 1. Disconnect the negative battery cable. 2. Disconnect the feed and module wire terminal connectors from the distributor cap. 3. Remove the ignition set retainer. 4. Remove the 4 coil cover-to-distributor cap screws and the coil cover. 5. Using a blunt drift, press the coil wire spade terminals up out of distributor cap. 6. Lift the coil up out of the distributor cap. 7. Remove and clean the coil spring, rubber seal washer and coil cavity of the distributor cap. To install: 8. Coat the rubber seal with a dielectric lubricant furnished in the replacement ignition coil package. 9. Install the coil spring, coil assembly and press the coil terminals into the distributor cap. Refer to the coil terminal illustration for terminal location. 10. Install the coil cover and torque the attaching screws to 60 inch lbs. (6 Nm). 11. Position the spark plug wire and retainer over the correct cap terminals, then engage the retainer and plug wires to the cap. Attach the distributor feed wires and negative battery cable. DISTRIBUTOR CAP See Figures 4 and 5 1. Disconnect the negative battery cable. 2. Remove the air cleaner, feed and module wire terminal connectors from the distributor cap. 3. Remove the retainer and spark plug wires from the cap. Remember to label them first. 4. Depress and release the 4 distributor cap-to-housing retainers and lift off the cap assembly. 5. Remove the four coil cover screws and cover. 6. Using a finger or a blunt drift, push the coil spade terminals up out of the distributor cap. 7. Remove all four coil screws and lift the coil, coil spring and rubber seal washer out of the cap coil cavity. 8. Using a new distributor cap, reverse the above procedures to assemble being sure to clean and lubricate the rubber seal washer with dielectric lubricant. Torque the coil cover attaching screws to 60 inch lbs. (6 Nm). Make sure the spark plug wire retainer and the four cap-to-housing retainers are fully engaged. Connect the negative battery cable. Fig. Fig. 4: Push down and twist the retainers to release the distributor cap, be sure to label the cap and wires to ease installation Fig. Fig. 5: Once all four retainers have been released, the distributor cap can be removed ROTOR See Figures 6 and 7 1. Disconnect the negative battery cable and remove the air cleaner assembly. 2. Disconnect the feed and module wire connectors from the distributor. 3. Depress and release the 4 distributor cap-to-housing retainers and lift off the cap assembly. 4. Remove the two rotor attaching screws and rotor. 5. Install the rotor, make sure the square shaft tab is properly engaged with the rotor and torque the retaining screws to 60 inch lbs. (6 Nm). Reinstall the cap and connect the negative battery cable. Fig. Fig. 6: Removing the rotor attaching screws Fig. Fig. 7: Lift the rotor straight up after removing the attaching screws VACUUM ADVANCE UNIT 1975-80 1. Disconnect the negative battery cable and remove the air cleaner. Remove the distributor cap and rotor as previously described. 2. Disconnect the vacuum hose from the vacuum advance unit. 3. Remove the two vacuum advance retaining screws, pull the advance unit outward, rotate and disengage the operating rod from its tang. 4. Install the vacuum advance and engage the operating rod, torque the screws to 60 inch lbs. (6 Nm) and install the distributor cap. 5. Install the air cleaner and connect the negative battery cable. MODULE See Figures 8 and 9 1. Disconnect the negative battery cable. Remove the air cleaner. 2. Remove the distributor cap and rotor as previously described. 3. Disconnect the harness connector and pick-up coil spade connectors from the module. Be careful not to damage the wires when removing the connector. 4. Remove the two screws and module from the distributor housing. 5. Coat the bottom of the new module with dielectric silicone lubricant supplied with the new module. Fig. Fig. 8: Be sure to coat the mating surfaces of the module To install: The silicone lubricant supplied with new modules MUST be applied, as it serves as a heat conductor and aids in module cooling. Running the engine and ignition system without the silicone lubricant is the equivalent of running the engine without antifreeze! That is, the module will cook itself without the lubricant! 6. Install the module and torque the retaining screws to 48 inch lbs. (5 Nm). 7. Connect the module wiring harnesses and install the distributor cap. 8. Connect the negative battery cable and install the air cleaner. Fig. Fig. 9: Disconnecting the module connector PICK-UP COIL See Figures 10, 11, 12 and 13 1. Disconnect the negative battery cable. 2. Remove the air cleaner assembly. 3. Mark the base of the distributor and the position of the rotor-to-housing. Remove the distributor-to-engine block retainer and bolt. Make sure the distributor base is marked with a scribe or grease pen for proper timing after installation. 4. Remove the distributor cap and disconnect the cap harnesses. 5. Twist and pull upward to remove the distributor assembly from the block. 6. Mark the distributor shaft and gear so they can be reassembled in the position. 7. Drive out the roll pin with a flat punch or equivalent. Fig. Fig. 10: Removing distributor roll-pin. 8. Remove the gear and pull the shaft out of the distributor housing. 9. Disconnect the pick-up harness. 10. Remove the three pick-up coil attaching screws and remove the magnetic shield, C washer, pick-up coil, magnet and pole piece. Fig. Fig. 11: Pick-up coil removed and disassembled To install: 11. Install the pick-up coil so wires go through the opening provided. 12. Install the magnet, pole piece and torque the three screws to 50 inch lbs. (5 Nm). 13. Clean the shaft with solvent to remove the varnish to ease installation. 14. Install the C washer, shaft, gear and tap in the roll pin. Make sure the marks are lined up. Connect the pick-up wiring harness. 15. Install the distributor into the block at the original marked position. WARNING 1 Make sure the distributor seats into the block fully. The base of the housing will stick up about /4of an inch until the distributor gear engages the oil pump drive. Damage to the oil pump, distributor and engine may result if the distributor is forced into position by tightening the distributor retainer bolt. If the distributor will not fully seat, grab the housing and shaft, twist and wiggle until the distributor drops into the oil pump drive. If this does not work, install a socket wrench onto the large bolt on the front of the crankshaft pulley. Slowly turn the crankshaft in either direction until the distributor drops into the block fully. 16. Install the distributor and retainer. Hand tighten the bolt at this time. 17. Install the distributor cap, connect the wiring harness and negative battery cable. 18. Plug all disconnected vacuum lines, install a inductive timing light and adjust the timing to specifications. Refer to the underhood sticker and timing procedures in this section for more information. 19. Install the air cleaner and connect the vacuum hoses. Fig. Fig. 12: Removing the distributor hold-down bolt Fig. Fig. 13: After removing the distributor, be sure to mark the gear and distributor shaft Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Description and Operation See Figure 1 Print The General Motors HEI system is a pulse-triggered, transistor controlled, inductive discharge electronic ignition system. The entire ignition system is contained within the distributor cap. The distributor, in addition to housing the mechanical and vacuum advance mechanisms (1975 through 1980), contains the ignition coil, the electronic control module, and the magnetic triggering device. The magnetic pick-up assembly contains a permanent magnet, a pole piece with internal teeth, and a pick-up coil (not to be confused with the ignition coil). All spark timing changes in the 1981 and later distributors are done electronically by the Electronic Control Module (ECM), which monitors information from various engine sensors, computes the desired spark timing and then signals the distributor to change the timing accordingly. No vacuum or mechanical advance units are used. In the HEI system, as in other electronic ignition systems, the breaker points have been replaced with an electronic switch (a transistor), which is located within the control module. This switching transistor performs the same function the points did in older conventional ignition systems; it simply turns coil primary current on and off at the correct time. So, electronic and conventional points-type ignition systems operate on the same basic principle. The module which houses the switching transistor is controlled (turned on and off) by a magnetically generated impulse, induced in the pick-up coil. When the teeth of the rotating "timer" align with the teeth of the pole piece, the induced voltage in the pick-up coil signals the electronic module to allow current to flow to the coil primary circuit. As the rotating "timer" moves away from the pole piece, the electronic module is signaled to stop the current flow to the primary circuit, and high voltage is induced in the ignition coil secondary windings which is then directed through the rotor and spark plug wires to fire the spark plugs. In essence, the pick-up coil module system simply replaces the conventional breaker points and condenser. The condenser found within the distributor is for radio suppression purposes only and has nothing to do with the ignition process. The module automatically controls the dwell period, increasing it with increasing engine speed. Since dwell is automatically controlled, it cannot be adjusted. The module itself is non-adjustable and non-repairable and must be replaced if found defective. Fig. Fig. 1: HEI distributor, exploded view Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Diagnosis and Testing See Figure 1 Print The symptoms of a defective component within the HEI system are exactly the same as those you would encounter in a conventional system. Some of these symptoms are: Hard or No Starting Rough Idle Poor Fuel Economy Engine misses under load or while accelerating. If you suspect a problem in your ignition system, there are certain preliminary checks which you should carry out before you begin to check the electronic portions of the system. First, it is extremely important to make sure the vehicle battery is in a good state of charge. A defective or poorly charged battery will cause the various components of the ignition system to read incorrectly when they are being tested. Second, make sure all wiring connections are clean and tight, not only at the battery, but also at the distributor cap, ignition coil, and at the electronic control module. Instruments designed specifically for testing HEI systems are available from several tool manufacturers. Some of these will even test the module itself. However, the tests given in this section will require only an ohmmeter and a voltmeter. CAUTION The HEI ignition system can generate voltage of 30,000-50,000 volts. When testing the system, DO NOT hold a spark plug wire while the engine is running or cranking. Personal injury and or damage to the ignition system may result if this caution is not followed. Since the only change between electronic and conventional ignition systems is in the distributor component area, it is imperative to check the secondary ignition circuit first. If the secondary circuit checks out properly, then the engine condition is probably not the fault of the ignition system. If the engine won't start, perform this test. This will narrow the problem area down considerably. 1. Remove one of the plug wires and insert a HEI spark tester tool in the plug socket. 2. Ground the spark tester to the block and crank the engine. DO NOT touch the spark plug wire while the engine is cranking. 3. The spark should be crisp and bright blue in color. If a normal spark occurs, try each spark plug wire until a no spark condition or a weak orange color spark is found. If all sparks are good, the problem is probably not in the ignition system. Check for fuel system problems, or fouled spark plugs. If no spark occurs, check for the presence of normal battery voltage at the battery (BAT) terminal in the distributor cap. The ignition switch must be in the ON position for this test. Either a voltmeter or a test light may be used for this test. Connect the test light wire to ground and the probe end to the BAT terminal at the distributor. If the light comes on, you have voltage to the distributor. If the light fails to come on, this indicates an open circuit in the ignition primary wiring leading to the distributor. In this case, you will have to check wiring continuity back to the ignition switch using a test light. If there is battery voltage at the BAT terminal, but no spark at the plugs, then the problem lies within the distributor assembly. Go on to the distributor components test section. Fig. Fig. 1: Ignition coil terminal location If the engine runs, but runs roughly or cuts out, make sure the plug wires are in good shape first. There should be no obvious cracks or breaks. You can check the plug wires with an ohmmeter, but do not pierce the wires with a probe. If the plug wires are OK, remove the cap assembly and check for moisture, cracks, chips, carbon tracks, or any other high voltage leaks or failures. Replace the cap if any defects are found. Make sure the timer wheel rotates when the engine is cranked. If everything is all right so far, go on to the distributor components test section. DISTRIBUTOR COMPONENTS TESTING See Figures 2 and 3 If the trouble has been narrowed down to the units within the distributor, the following tests can help pinpoint the defective component. An ohmmeter with both high and low ranges should be used. These tests are made with the cap assembly removed and the battery wire disconnected. If a tachometer is connected to the TACH terminal, disconnect it before making these tests. 1. Connect an ohmmeter between the TACH and BAT terminals in the distributor cap. The primary coil resistance should be 0&omega or nearly 0&omega . If not replace the coil. 2. To check the coil secondary resistance, connect an ohmmeter between the rotor button and the BAT terminal. Note the reading. Connect the ohmmeter between the rotor button and the TACH terminal. Note the reading. The resistance in both cases should be between 6,000 and 30,000&omega. Be sure to test between the rotor button and both the BAT and TACH terminals. 3. Replace the coil only if the readings in Step 1 and Step 2 are infinite resistance or out of specification. Fig. Fig. 2: Checking coil resistance. Ohmmeter 1 shows primary test. Ohmmeter 2 shows secondary test. These resistance checks will not disclose shorted coil windings. This condition can only be detected with scope analysis or a suitably designed coil tester. If these instruments are unavailable, replace the coil with a known good coil as a final coil test. 4. To test the pick-up coil, first disconnect the white and green module leads. Set the ohmmeter on the high scale and connect it between a ground and either the white or green lead. Any resistance measurement less than infinite requires replacement of the pick-up coil. 5. Pick-up coil continuity is tested by connecting the ohmmeter (on low range) between the white and green leads. Normal resistance is between 650 and 850&omega, or 500 and 1,500&omega on 1977 and later models. Move the vacuum advance arm while performing this test (early models). This will detect any break in coil continuity. Such a condition can cause intermittent misfiring. Replace the pick-up coil if the reading is outside the specified limits. 6. If no defects have been found at this time, and you still have a problem, then the module will have to be checked. If you do not have access to a module tester, the only possible alternative is a substitution test. If the module fails the substitution test, replace it. Fig. Fig. 3: Pick-up coil testing Back to Top Engine & Engine Overhaul GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Alternator The alternating current generator (alternator) supplies a continuous output of electrical energy at all engine speeds. The belt-driven Print alternator generates electrical energy and recharges the battery by supplying it with electrical current. The alternator consists of four main assemblies; two end frame assemblies, a stator assembly, and a rotor assembly. The rotor assembly is supported in the drive end frame by a ball bearing and at the other end by a roller bearing. These bearings are permanently lubricated and require no maintenance. There are six diodes in the end frame assembly. These diodes are electrical check valves that also change the alternating current developed within the stator windings to direct current (DC) at the output (BAT) terminal. Three of these diodes are negative and are mounted flush with the end frame while the other three are positive and are mounted into a component called a heat sink (which serves as a reservoir for excess heat, thus protecting the alternator). The positive diodes are easily identified as the ones within small cavities or depressions. No periodic adjustments or maintenance of any kind, except for regular belt adjustments, are required on the entire alternator assembly. Alternator output in amps, is sometimes stamped on the case of each unit, near the mounting hole. Regulator voltages range between 13.6 and 16 volts at 75°F. ALTERNATOR PRECAUTIONS WARNING To prevent serious damage to the alternator and the rest of the charging system, the following precautions must be observed: 1. When installing a battery, make sure that the positive cable is connected to the positive terminal and the negative to the negative. 2. When jump-starting the vehicle with another battery, make sure that like terminals are connected. This also applies when using a battery charger. 3. Never operate the alternator with the battery disconnected or otherwise on an uncontrolled open circuit. Double-check to see that all connections are tight. 4. Do not short across or ground any alternator or regulator terminals. 5. Do not try to polarize the alternator. 6. Do not apply full battery voltage to the field (brown) connector. 7. Always disconnect the battery ground cable before disconnecting the alternator lead. TESTING See Figures 1 and 2 If you suspect a defect in your charging system, first perform these general checks before going on to more specific tests. 1. Check the condition of the alternator belt and tighten if necessary. 2. Clean the battery cable connections at the battery. Make sure the connections between the battery wires and the battery clamps are good. Reconnect the negative terminal only and proceed to the next step. 3. With the key off, insert a test light between the positive terminal on the battery terminal clamp. If the test light comes on, there is a short in the electrical system of the vehicle. The short must be repaired before proceeding. If the light does not come on, then proceed to the next step. If the vehicle is equipped with an electric clock, the clock must be disconnected. 4. Check the charging system wiring for any obvious breaks or shorts. 5. Check the battery to make sure it is fully charged and in good condition. Operational Test You will need a current indicator to perform this test. If the current indicator is to give an accurate reading, the battery cables must be the same gauge and length as the original equipment. 1. With the engine running and all electrical systems turned off, place a current indicator over the positive battery cable. 2. If a charge of roughly five amps is recorded, the charging system is working. If a draw of about five amps is recorded, the system is not working. The needle moves toward the battery when a charge condition is indicated, and away from the battery when a draw condition is indicated. 3. If a draw is indicated, proceed with further testing. If an excessive charge (10-15 amps) is indicated, the regulator may be at fault. Output Test 1975 TO 1987 SI SERIES 1. You will need an ammeter for this test. 2. Disconnect the battery ground cable. 3. Disconnect the wire from the battery terminal on the alternator. 4. Connect the ammeter negative lead to the battery terminal wire removed in step three, and connect the ammeter positive lead to the battery terminal on the alternator. 5. Reconnect the battery ground cable and turn on all electrical accessories. If the battery is fully charged, disconnect the coil wire and bump the starter a few times to partially discharge it. 6. Start the engine and run it until you obtain a maximum current reading on the ammeter. 7. If the current is within ten amps of the rated output of the alternator, the alternator is working properly. If the current is not within ten amps, insert a probe into the test hole in the end frame of the alternator and ground the tab in the test hole against the side of the hole. The 1975-87 SI series alternator is equipped with the test hole, where the 1987 to present CS series alternator is not equipped with a test hole. 8. If the current is now within ten amps of the rated output, remove the alternator and have the voltage regulator replaced. If it is still below ten amps of rated output, have the alternator repaired. See the alternator and regulator output chart in this section. Fig. Fig. 1: SI series alternator test hole 1987 TO 1990 CS SERIES The CS series alternator comes in a variety of sizes as does the SI series. The most used sizes are the 130 and 144. These numbers represent the outside diameter of the stator laminations in millimeters. The main difference between the CS and SI series is the newly designed voltage regulator and the absence of a diode trio. The remaining components are basic to the earlier SI models. The CS series may have a combination of a four terminal connector at the alternator. All or only two connections may be used depending on the vehicle. The terminals are labeled S, F, L, P. The P terminal is connected to the stator and a diesel tachometer, if so equipped. The L terminal is connected to the charge indicator bulb. The F terminal is connected internally to the field positive and may be used as a fault indicator. The S terminal may be connected to a external voltage source, such as battery voltage. The P, F and S terminals are optional. 1. Check all preliminary charging system tests before continuing. 2. With the ignition switch ON and the engine NOT running, the alternator lamp should be ON. If not, check for an open circuit between the grounding lead and ignition switch. Check for a burned out bulb. 3. With the engine RUNNING at moderate speed, the lamp should be OFF. If not, turn OFF the engine and disconnect the harness connector at the alternator. Start the engine and check the lamp. If the lamp goes OFF, repair or replace the alternator. If the lamp stays ON, check for a grounded L terminal wire in the harness. 4. Is the battery undercharged or overchargedA. Disconnect the wiring harness connector from the alternator. B. With ignition switch ON, engine NOT running, connect a voltmeter from ground to the L terminal. A zero reading indicates an open circuit between the terminal and battery. C. Reconnect the harness connector and run the engine at moderate speed. Measure the voltage across the battery. If it is above 16V, repair or replace the alternator. D. Turn on all accessories, load the battery with a carbon pile to obtain maximum amperage. Maintain voltage at 13V or greater. If the amperage is within 15 amps of rated output, the alternator is OK. If NOT within 15 amps, replace or repair the alternator. Fig. Fig. 2: CS series alternator REMOVAL & INSTALLATION See Figures 3, 4, 5, 6 and 7 1. Disconnect the battery ground cable to prevent diode damage. 2. Tag and disconnect the alternator wiring. 3. Remove the alternator brace bolt. If the vehicle is equipped with power steering, loosen the pump brace and mount nuts. Detach the drive belt(s). 4. Support the alternator and remove the mount bolt(s). Remove the unit from the vehicle. To install: 5. To install, position the alternator into the mounting brackets and hand tighten the mounting bolts. Alternator belt tension is quite critical. A belt that is too tight may cause alternator bearing failure; one that is too loose will cause a gradual battery discharge as well as belt wear. For details on correct belt adjustment, see Drive Belts in Routine Maintenance . When adjusting alternator belt tension, apply pressure at the center of the alternator unit, NEVER against either end frame. Fig. Fig. 3: Alternator mounting on most late model engines Fig. Fig. 4: Disconnect the electrical connectors from the back of the alternator Fig. Fig. 5: Disconnect the connection at the top of the alternator Fig. Fig. 6: Remove the alternator attaching bolts Fig. Fig. 7: Once the belt is slipped off and all bolts/wiring removed, the alternator can be removed from the vehicle Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Battery REMOVAL & INSTALLATION Print CAUTION When working on the battery, be careful at all times to keep metal wrenches from connecting across the battery terminal posts. DO NOT wear any type of metal jewelry, this includes watches! 1. Use a wrench to loosen the through-bolt for the terminal. If necessary, use a prybar to carefully spread the terminal halves apart. Disconnect the negative terminal. Then, repeat the process to disconnect the positive terminal. 2. Remove the retainer screw from the retaining block located behind the battery. Remove the retainer. 3. Carefully lift the battery out of the engine compartment using a battery lifting strap or equivalent. 4. Thoroughly clean the entire battery box area. Use a mild solution of baking soda and water to cut through the corrosion. This is done because the battery retains its charge better in a clean environment. 5. Replace the battery with one having an equal or higher rating in amp/hours. Note that the older a vehicle is, the more likely it is to benefit from an increase in battery capacity due to increased resistance in the wiring. 6. Replace the battery in exact reverse order, making sure it is securely mounted before starting to connect the wiring. Make sure the battery terminals are clean, using a special brush designed for that purpose, if necessary. 7. Connect the positive terminal first, and then the negative, tightening them securely. Coat the terminals with petroleum jelly to protect them from corrosion. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide High Energy Ignition (HEI) Distributor The Delco-Remy High Energy Ignition (HEI) system is a breakerless (has no ignition points), pulse triggered, transistor controlled, inductive discharge ignition system that is standard on the Buick, Olds and Pontiac vehicles covered in this guide. Print There are only nine electrical connections in the system; the ignition switch feed wire and the eight spark plug leads (early models). After 1980, the EST wiring harness has to be disconnected. On most models, the coil is located in the distributor cap, connecting directly to the rotor. The magnetic pick up assembly located inside the distributor contains a permanent magnet, a pole piece with internal teeth, and a pick up coil. When the teeth of the rotating timer core and pole piece align, an induced voltage in the pick-up coil signals the electronic module to open the coil primary circuit. As the primary current decreases, a high voltage is induced in the secondary windings of the ignition coil directing a spark through the rotor and high voltage leads to fire the spark plugs. The dwell period is automatically controlled by the electronic module and is increased with increasing engine rpm. The HEI system features, as do most electronic ignition systems, a longer spark duration which is instrumental in firing today's lean and EGR-diluted fuel/air mixtures (a lean mixture requires a much hotter, longer duration spark to ignite it than does a rich mixture). A capacitor, which looks like the condenser in the old points-type ignition systems, is located within the HEI distributor and is used for noise (static) suppression in conjunction with the vehicle's radio. The capacitor is not a regularly replaced component. As noted in Engine Electrical , 1981 and later models continue to use the HEI distributor, although it now incorporates an Electronic Spark Timing system. With the EST system, all spark timing changes are performed electronically by the Electronic Control Module (ECM) which monitors information from various engine sensors, computes the desired spark timing and then signals the distributor to change the timing accordingly. Because all timing changes are controlled electronically, no vacuum or mechanical advance systems are used. REMOVAL & INSTALLATION Engine Not Disturbed Do not rotate the engine while the distributor is removed in order to make installing it simpler and easier. If the engine is inadvertently disturbed while the distributor is out, please refer to the appropriate procedure. 1. Disconnect the ground cable from the battery. On 1984 and later models, disconnect the ignition switch battery feed wire and, if the vehicle is equipped with a tach, the tachometer lead from the cap. 2. Tag and disconnect the feed and module terminal connectors from the distributor cap. DO NOT use a screwdriver to release the terminal connectors. 3. On 1975-80 models, disconnect the hose at the vacuum advance unit. 4. Depress and release the 4 distributor cap-to-housing retainers and lift off the cap assembly. 5. Using a magic marker, matchmark the rotor-to-housing and housing-to-engine block positions so they can be matched during installation. The distributor must be installed with the rotor and housing in the correct position. 6. Loosen and remove the distributor clamp and bolt. Carefully lift the distributor just until the point where the rotor stops turning. Be careful not to disturb the position of the rotor. Now, again mark the relative positions of the rotor-to-distributor housing. The rotor must be aligned with this position before you engage distributor and camshaft drive gears during installation. To install: 7. With a new O-ring on the distributor housing and the rotor aligned with the second mark, install the distributor, taking care to align the mark on the housing with the one on the engine. It may be necessary to lift the distributor and turn the rotor slightly to align the gears and the oil pump driveshaft. WARNING 1 Make sure the distributor seats into the block fully. The base of the housing will stick up about /4in. until the distributor gear engages the oil pump drive. Damage to the oil pump, distributor and engine may result if the distributor is forced into position by tightening the distributor clamp bolt. If the distributor will not fully seat, grab the housing and shaft, twist and wiggle until the distributor drops into the oil pump drive. If this does not work, install a socket wrench onto the large bolt on the front of the crankshaft pulley. Slowly turn the crankshaft in either direction until the distributor drops into the block fully. 8. With the respective marks aligned, install the clamp and the bolt finger-tight. 9. Install and secure the distributor cap. 10. Connect the feed and module connectors to the distributor cap. Reconnect the ignition switch battery feed wire and tach connector where necessary. 11. Connect a timing light to the engine and plug the vacuum hose, if so equipped. 12. Connect the ground cable to the battery. 13. Start the engine and set the timing to specifications. 14. Turn the engine off and torque the distributor clamp bolt to 15 ft. lbs. (20 Nm). Disconnect the timing light and unplug and disconnect the hose to the vacuum advance. Engine Disturbed CAUTION The engine MUST be completely cooled down before performing this procedure. A hot engine may cause burns and personal injury. 1. Disconnect the negative battery cable. 2. Remove the No. 1 cylinder spark plug. Turn the engine using a socket wrench on the large bolt on the front of the crankshaft pulley. Place a finger near the No. 1 spark plug hole and turn the crankshaft until the piston reaches Top Dead Center (TDC). As the engine approaches TDC, you will feel air being expelled by the No. 1 cylinder. If the crankshaft timing indicator says TDC has been reached but the other condition is not being met, turn the engine another full turn (360 degree). Once the engine's position is correct, replace the spark plug. Line the mark on the crankshaft damper with the 0 degree mark on the timing indicator. When the timing marks are lined up at 0 degree, the No. 1 piston can be either on the exhaust stroke or the compression stroke. But only on the compression stroke will air be forced from the hole (on the exhaust stroke, then exhaust valve is open allowing air to escape through the manifold. Therefore, when air is felt being forced out of the spark plug hole, you can be sure the cylinder is on its compression stroke. The timing will be incorrect if the distributor is installed while aligning the rotor to fire that spark plug on the exhaust stroke. 3. Using the firing order illustration if necessary, find No. 1 cylinder on the distributor cap. Turn the rotor until the rotor contact is approximately aligned with the wire going to No. 1 cylinder, as if the distributor had just fired No. 1 cylinder. Install the distributor as described above, turning the rotor slightly to mesh the gear teeth and oil pump driveshaft so that the rotor comes out in the proper position. Make sure the distributor is fully seated in the block before tightening the hold-down clamp. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Ignition Coil TESTING Print See Figure 1 Coil-in-Cap 1. Remove the distributor cap from the housing assembly. For details, please refer to Engine Electrical of this information. 2. Connect an ohmmeter across the primary connections, as shown by the ohmmeter and wiring on the left side (#1) of the illustration. The resistance should be zero or very close to zero. High resistance or infinite resistance indicates a partial or complete open circuit, and the need to replace the coil. 3. Connect the ohmmeter between the primary ground and the coil secondary connector. Set the resistance to the higher scale. Test resistance as shown by the solid wire connections and then repeat the test with the wire connected as shown by the dotted line. If both readings are infinite, the coil is bad. If both or either show continuity, the coil is okay. Fig. Fig. 1: Testing the ignition coil - distributor cap mounted coil assemblies Separately Mounted Coil See Figure 2 Fig. Fig. 2: Testing the ignition coil - separately (external) mounted coil 1. Disconnect the secondary lead and unplug the primary leads. Remove the mounting bolts and remove the coil from the engine. 2. First connect an ohmmeter, set to the high scale, as shown on the left (#1) in the illustration. The resistance should be nearly infinite. If it is not, replace the coil. 3. Connect the ohmmeter as shown in the center picture. Use the low resistance scale. The reading should be very low, nearly zero. Otherwise, replace the coil. 4. Reset the ohmmeter to the high resistance scale and connect it as shown on the right. There should be obvious continuity; the ohmmeter should not read infinite. If it does replace the coil. If all three tests are passed, the coil is satisfactory. REMOVAL & INSTALLATION 1. Mark the high tension wires. Then, carefully disconnect each from the distributor cap. Squeeze the latches together and then disconnect the connector that runs from the cap to the distributor base. 2. Use a large, flat bladed prybar to first depress and then rotate the wire type latch away from the underside of the distributor on either side. Remove the cap. 3. Turn the cap upside down. Remove the four bolts from the four corners of the coil, noting the location of the secondary ground lead. Then, remove the primary wiring from the connector in the cap, noting the routing of positive and negative leads. 4. Remove the coil and wiring. Then, remove the arc seal from underneath. 5. Wipe the mounting area for the coil clean with a soft cloth. Inspect the cap for defects, especially heat or carbon tracks, and replace it if necessary. 6. Install a new coil into position, and carefully route the primary wiring positive and negative leads properly. 7. Position the coil ground wire as it was at removal and then install and snug up the four coil mounting bolts. Install the cap and wiring in reverse order. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Ignition Module REMOVAL & INSTALLATION Print 1. Mark the high tension wires. Then, carefully disconnect each from the distributor cap. Squeeze the latches together and then disconnect the connector that runs from the cap to the distributor base. 2. Use a large, flat bladed prybar to first depress and then rotate the wire type latch away from the underside of the distributor on either side. Remove the cap. 3. Carefully note the colors of the two leads. Mark them, if necessary. Then disconnect them. 4. Remove the two module attaching screws and pull the module upward and out, being careful not to disturb the grease, if the module may be reused. To install: The module is mounted via a thick layer of grease. This grease is analogous to the coolant in an engine. It carries intense heat away from the module. Make sure to coat the lower surface of the module, as well as the mounting surface in the distributor with the grease included in the packed with the new module if the module is replaced. Make sure not to disturb the old grease layer on the old module if it is to be re-used. Failure to do this will cause the module to fail prematurely! 5. Remount the module, connect the leads in the proper order, tighten the retaining screws and reinstall the distributor cap. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Regulator The voltage regulator works with the battery and alternator to comprise the charging system. As the voltage regulator's name e implies, it Print regulates the voltage output of the alternator to a safe level (so the alternator does not overcharge the battery). A properly working regulator also prevents excessive voltage from burning out wiring, bulbs and other electrical components. All Buick, Olds and Pontiac models covered in this guide are equipped with integral regulators, which are built into the alternator case. The regulators are solid state and require no maintenance or adjustment. REMOVAL & INSTALLATION See Figures 1, 2 and 3 1975-1987 SI Series 1. Remove the alternator from the vehicle. Position the assembly in a suitable holding fixture. 2. Make scribe marks on the case end frames to aid in reassembly. 3. Remove the through bolts. Separate the drive end frame assembly from the rectifier end frame assembly. 4. Remove the rectifier attaching nuts and the regulator attaching screws from the end frame assembly. Note the position of the screws with the insulated washers for reassembly. 5. Remove the voltage regulator from the end frame assembly. To install: 6. Position the brushes in the brush holder and retain them in place using a brush retainer wire or equivalent. 7. Assemble the brush holder, regulator, resistor, diode trio and rectifier bridge to the end frame. Be sure to assemble the screws with the insulated washers in the correct locations. 8. Assemble the end frames together with the through bolts. Remove the brush retainer wire. Fig. Fig. 1: Regulator mounting on SI series alternators Fig. Fig. 2: On all alternator models, the brushes can be retained with a wire in the holder 1987-1990 CS Series TYPE 130 1. Remove the alternator from the vehicle. Scribe marks on the end frames to facilitate assembly. Remove the through bolts and separate the end frames. 2. Remove the cover rivets or pins and remove the cover. 3. Unsolder the stator leads at the three terminals on the rectifier bridge. Avoid excessive heat, as damage to the assembly will occur. Remove the stator. 4. Remove the brush holder screw. Disconnect the terminal and remove the brush holder assembly. 5. Unsolder and pry open the terminal between the regulator and the rectifier bridge. Remove the terminal and the retaining screws. Remove the regulator and the rectifier bridge from the end frame. To install: 6. Position the brushes in the brush holder and retain them in place using a brush retainer wire or equivalent. 7. Assembly is the reverse of disassembly. Be sure to remove the brush retainer wire when the alternator has been reassembled. TYPE 144 1. Remove the alternator from the vehicle. Scribe marks on the end frames to facilitate assembly. Remove the through bolts and separate the end frames. 2. Remove the stator attaching nuts and the stator from the end frame. 3. Unsolder the connections, remove the retaining screws and connector from the end frame. Separate the regulator and brush holder from the end frame. To install: 4. Position the brushes in the brush holder and retain them in place using a brush retainer wire or equivalent. 5. Assembly is the reverse of disassembly. Be sure to remove the brush retainer wire when the alternator has been reassembled. Fig. Fig. 3: Regulator mounting on CS series alternators Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Safety Precautions Observing these precautions will ensure safe handling of the electrical system components, and will avoid damage to the vehicle's electrical system: Print Be absolutely sure of the polarity of a booster battery before making connections. Connect the cables positive-to-positive, and negative-to-negative. Connect positive cables first and then make the last connection to a ground on the body of the booster vehicle so that arcing cannot ignite hydrogen gas that may have accumulated near the battery. Even momentary connection of a booster battery with the polarity reserved will damage alternator diodes. Disconnect both vehicle battery cables before attempting to charge a battery. Never ground the alternator output or battery terminal. Be cautious when using metal tools around a battery to avoid creating a short circuit between the terminals. Never ground the field circuit between the alternator and regulator. Never run an alternator or generator without load unless the field circuit is disconnected. Never attempt to polarize an alternator. Never wear metal jewelry when working on any electrical system. This includes watches! Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Sending Units and Sensors REMOVAL & INSTALLATION Print See Figures 1 and 3 Coolant Temperature 1. Disconnect the negative battery cable. 2. Drain the coolant to a level below the coolant temperature sensor or sending unit. 3. Disconnect the electrical connection. 4. Remove the sensor or sending unit from the engine. 5. Installation is the reverse of removal. Torque to 23 ft. lbs (32 Nm). Fig. Fig. 1: Common sensor locations on V6 engines Oil Pressure 1. Disconnect the negative battery cable. 2. Disconnect the electrical connector. 3. Remove the sending unit from the engine. 4. Installation is the reverse of removal. Torque to 23 ft. lbs (32 Nm). See Figure 2 Fig. Fig. 2: Common sensor locations on V8 gasoline engines Knock Sensor 1. Disconnect the negative battery cable. 2. On some vehicles, it may be necessary to raise the car to access the sensor. Be sure to properly secure it. 3. Disconnect the electrical connector from the sensor. 4. Remove the sensor from the engine. 5. Installation is the reverse of removal. Apply a thread sealer, such as a soft sealing tape, to the ESC sensor threads. Torque to 23 ft. lbs (32 Nm). Fig. Fig. 3: Sensor locations on diesel engines Oxygen Sensor The oxygen sensor may be difficult to remove when the engine temperature is below 120°F (48°C). Excessive force may damage the threads in the exhaust manifold or pipe. Care must be taken during removal. 1. Disconnect the negative battery cable. 2. Disconnect the electrical connector. 3. Carefully remove the oxygen sensor using a special sensor removal tool. To install: 4. Coat the threads of the sensor with a special oxygen sensor anti-seize compound. Do not use a anti-seize compound not made for oxygen sensors. 5. Install the sensor and torque to 30 Ft. lbs (41 Nm). 6. Connect the electrical connector and negative battery cable. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Starter REMOVAL & INSTALLATION Print See Figures 1, 2, 3, 4 and 5 Gasoline Engines The starters on some engines require the addition of shims to provide proper clearance between the starter pinion gear and the flywheel. These shims are available in 0.015 in. (0.4mm) sizes from Buick, Oldsmobile and Pontiac dealers. Flat washers can be used if shims are unavailable. 1. Important: disconnect the negative battery cable before proceeding. 2. Raise the vehicle to a convenient working height and safely support it with jackstands. 3. Remove the exhaust crossover pipe. 4. Disconnect all wiring from the starter solenoid. Replace each nut as the connector is removed, as thread sizes differ from connector to connector. Tag the wires for later connection. 5. Remove the flywheel housing cover and disconnect the oil cooler lines at the transmission, if necessary. 6. Starter removal on certain models may necessitate the removal of the frame support. This support runs from the corner of the frame to the front crossmember. To remove: A. Loosen the mounting bolt that attaches the support to the corner of the frame. B. Loosen and remove the mounting bolt that attaches the support to the front crossmember and then swing the support out of the way. C. Install the crossmember and mounting bolts. Torque the bolts to 80 ft. lbs. (109 Nm). 7. Remove the front bracket from the starter and the two mounting bolts. On engines with a starter solenoid heat shield, remove the front bracket upper bolt and detach the bracket from the starter. 8. Remove the front bracket bolt or nut. Lower the starter front end first, then remove the unit from the vehicle. 9. Installation is the reverse of removal. Make sure that any shims removed are replaced (please refer to the shimming procedure). Torque the two mounting bolts to 25-35 ft. lbs. (34-48 Nm). Connect the starter wires and install heat shields if removed. Fig. Fig. 1: It may be necessary to remove the flywheel cover on some models to remove the starter Fig. Fig. 2: On some models it may be helpful to disconnect the cooler lines at the transmission before removing the flywheel cover Fig. Fig. 3: Removing the starter attaching bolts Fig. Fig. 4: To remove the starter from the vehicle, first pull it straight out then lower it away from the vehicle Fig. Fig. 5: On some models the connections at the starter solenoid are not accessible when it is installed. Do not let the starter hang by it's wires once it has been lowered from it's mount. Have a helper hold it, then disconnect the wires Diesel Engines 1. Disconnect both batteries. Raise the vehicle and support it securely with jackstands. 2. Remove the flywheel cover. 3. Remove the starter heat shield upper bolt and side nut and then remove the shield. 4. Label the wires and then disconnect them, keeping attaching nuts in order. On the Olds 88 and 98 models, it may be necessary to work on the wiring from the front of the engine. 5. Support the starter from underneath. Remove the two mounting bolts that can be reached from underneath the starter, and remove it by pulling it out between the flywheel and exhaust crossover. To install: 6. Support the starter and connect the wiring harness as previously marked. 7. Position the starter into the mounting area and install the shims (if used) and mounting bolts. Torque the mounting bolts to 35 ft. lbs. (47 Nm). 8. Install the flywheel cover and heat shield, if so equipped. 9. Connect the battery cables and start the engine to check for proper operation. SHIMMING See Figures 6 and 7 Starter noise during cranking and after the engine fires is often a result of too much or too little distance between the starter pinion gear and the flywheel. A high pitched whine during cranking (before the engine fires) can be caused by the pinion and flywheel being too far apart. Likewise, a whine after the engine starts (as the key is released) is often a result of the pinion-flywheel relationship being too close. In both cases flywheel damage can occur. Shims are available in 0.015 in. (0.4mm) sizes to properly adjust the starter on its mount. You will also need a flywheel turning tool, available at most auto parts stores or from any auto tool store or salesperson. If your vehicle's starter emits the above noises, follow the shimming procedure: 1. Disconnect the negative battery cable. 2. Remove the flywheel inspection cover on the bottom of the bellhousing. 3. Using the flywheel turning tool, turn the flywheel and examine the flywheel teeth. If damage is evident, the flywheel should be replaced. 4. Insert a suitable prybar into the small hole in the bottom of the starter and move the starter pinion and clutch assembly so the pinion and flywheel teeth mesh. If necessary, rotate the flywheel so that a pinion tooth is directly in the center of the two flywheel teeth and on the centerline of the two gears, as shown in the accompanying illustration. 5. Check the pinion-to-flywheel clearance by using a 0.020 in. (0.5mm) wire gauge (a spark plug wire gauge may work here, or you can make your own). Make sure you center the pinion tooth between the flywheel teeth and the gauge, NOT in the corners, as you may get a false reading. If the clearance is under this minimum, shim the starter away from the flywheel by adding shim(s) one at a time to the starter mount. Check clearance after adding each shim. 6. If the clearance is a good deal over 0.020 in. (0.5mm), in the vicinity of 0.050 in. (1.27mm) plus, shim the starter toward the flywheel. Broken or severely mangled flywheel teeth are also a good indicator that the clearance here is too great. Shimming the starter toward the flywheel is done by adding shims to the outboard starter mounting pad only. Check the clearance after each shim is added. A shim of 0.015 in. (0.4mm) at this location will decrease the clearance about 0.010 in. (0.25mm). Fig. Fig. 6: Shimming the starter; diesel shown at right Fig. Fig. 7: Checking the pinion-to-flywheel clearance SOLENOID REPLACEMENT See Figure 8 1. Disconnect the negative battery cable. 2. Remove the starter motor from the vehicle as previously outlined. 3. Remove the screw and washer from the field strap terminal. 4. Remove the two solenoid-to-housing retaining screws and the motor terminal bolt. 5. Remove the solenoid by twisting the unit 90 degrees. To install: 6. Install the solenoid and twist 90 degrees. Make sure the return spring is on the plunger, and rotate the solenoid unit into place on the starter. 7. Install the retaining screws and torque to 100 inch lbs. (11 Nm). 8. Connect the field strap terminal, install the starter, connect the negative battery cable and start the engine to check for proper operation. Fig. Fig. 8: Exploded view of the solenoid assembly Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Understanding The Engine Electrical System The engine electrical system can be broken down into three separate and distinct systems: Print 1. The starting system 2. The charging system 3. The ignition system The battery is the first link in the chain of mechanisms which work together to provide cranking of the automobile engine. In most modern vehicles, the battery is a lead-acid electrochemical device consisting of six two-volt (2V) subsections connected in series so the unit is capable of producing approximately 12V of electrical pressure. Each subsection, or cell, consists of a series of positive and negative plates held a short distance apart in a solution of sulfuric acid and water. The two types of plates are of dissimilar metals. This causes a chemical reaction to be set up, and it is this reaction which produces current flow from the battery when its positive and negative terminals are connected to an electrical appliance such as a lamp or motor. The continued transfer of electrons would eventually convert the sulfuric acid in the electrolyte to water, and make the two plates identical in chemical composition. As electrical energy is removed from the battery, its voltage output tends to drop. Thus, measuring battery voltage and battery electrolyte composition are two ways of checking the ability of the unit to supply power. During the starting of the engine, electrical energy is removed from the battery. However, if the charging circuit is in good condition and the operating conditions are normal, the power removed from the battery will be replaced by the generator (or alternator) which will force electrons back through the battery, reversing the normal flow, and restoring the battery to its original chemical state. The battery and starting motor are linked by very heavy electrical cables designed to minimize resistance to the flow of current. Generally, the major power supply cable that leaves the battery goes directly to the starter, while other electrical system needs are supplied by a smaller cable. During the starter operation, power flows from the battery to the starter and is grounded through the vehicle's frame and the battery's negative ground strap. The starting motor is a specially designed, direct current electric motor capable of producing a very great amount of power for its size. One thing that allows the motor to produce a great deal of power is its tremendous rotating speed. It drives the engine through a tiny pinion gear (attached to the starter's armature), which drives the very large flywheel ring gear at a greatly reduced speed. Another factor allowing it to produce so much power is that only intermittent operation is required of it. Thus, little allowance for air circulation is required, and the windings can be built into a very small space. The starter solenoid is a magnetic device which employs the small current supplied by the starting switch circuit of the ignition switch. This magnetic action moves a plunger which mechanically engages the starter and electrically closes the heavy switch which connects it to the battery. The starting switch circuit consists of the starting switch contained within the ignition switch, a transmission neutral safety switch or clutch pedal switch, and the wiring necessary to connect these with the starter solenoid or relay. A pinion gear is mounted to a one-way drive clutch. This clutch is splined to the starter armature shaft. When the ignition switch is moved to the START position, the solenoid plunger slides the pinion toward the flywheel ring gear via collar and spring. If the teeth on the pinion and flywheel match properly, the pinion will engage the flywheel immediately. If the gear teeth butt one another, the spring will be compressed and will force the gears to mesh as soon as the starter turns far enough to allow them to do so. As the solenoid plunger reaches the end of its travel, it closes the contacts that connect the battery and starter, then the engine is cranked. As soon as the engines starts, the flywheel ring gear begins turning fast enough to drive the pinion at an extremely high rate of speed. At this point, the one-way clutch begins allowing the pinion to spin faster than the starter shaft so that the starter will not operate at excessive speed. When the ignition switch is released from the starter position, the solenoid is de-energized, and a spring contained within the solenoid assembly pulls the gear out of mesh and interrupts the current flow to the starter. Some starters employ a separate relay, mounted away from the starter, to switch the motor and solenoid current on and off. The relay thus replaces the solenoid electrical switch, but does not eliminate the need for a solenoid mounted on the starter used to mechanically engage the starter drive gears. The relay is used to reduce the amount of current the starting switch must carry. The automobile charging system provides electrical power for operation of the vehicle's ignition and starting systems, as well as for all electrical accessories. The battery serves as an electrical surge or storage tank, storing (in chemical form) the energy originally produced by the engine driven generator (alternator). The system also provides a means of regulating generator output to protect the battery from being overcharged and to avoid excessive voltage to the accessories. As stated earlier, the storage battery is a chemical device incorporating parallel lead plates in a tank containing a sulfuric acid-water solution. Adjacent plates are slightly dissimilar, and the chemical reaction of the two dissimilar plates produces electrical energy when the battery is connected to a load such as the starter motor. The chemical reaction is reversible, so that when the generator is producing a voltage (electrical pressure) greater than that produced by the battery, electricity is forced into the battery, which is then returned to its fully charged state. The vehicle's generator is driven mechanically, through V-belts, by the engine crankshaft. It consists of two coils of fine wire, one stationary (the stator) and one movable (the rotor). The rotor may also be known as the armature, and consists of fine wire wrapped around an iron core which is mounted on a shaft. The electricity which flows through the two coils of wire (provided initially by the battery in some cases) creates an intense magnetic field around both rotor and stator. The interaction between the two fields creates voltage, allowing the generator to power the accessories and charge the battery. Newer automobiles use alternating current generators or alternators because they are more efficient, can be rotated at higher speeds, and have fewer brush problems. In an alternator, the field rotates while all the current produced passes only through the stator windings. The brushes bear against continuous slip rings rather than a commutator. This causes the current produced to periodically reverse the direction of its flow. Diodes (electrical oneway switches) block the flow of current from traveling in the wrong direction. A series of diodes is wired together to permit the alternating flow of the stator to be converted to a pulsating, but unidirectional flow at the alternator output. The alternator's field is wired in series with the voltage regulator. Back to Top Driveability & Emissions Controls GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Air Injection Reactor System (A.I.R.) Print OPERATION See Figure 1 The AIR system injects compressed air into the exhaust system, near enough to the exhaust valves to continue burning the normally unburned segment of the exhaust gases. To do this it employs an air injection pump and a system of hoses, valves, tubes, etc., necessary to carry the compressed air from the pump to the exhaust manifolds. Carburetors and distributors for AIR engines have specific modifications to adapt them to the air injection system; those components should not be interchanged with those intended for use on engines that do not have the system. A diverter valve is used to prevent backfiring. The valve senses sudden increases in manifold vacuum and ceases the injection of air during fuel rich periods. During coasting, this valve diverts the entire air flow through the pump muffler and during high engine speeds, expels it through a relief valve. Check valves in the system prevent exhaust gases from entering the pump. Fig. Fig. 1: AIR system The AIR system on the V6 engines is slightly different, but its purpose remains the same. SERVICE The AIR system's effectiveness depends on correct engine idle speed and ignition timing. These settings should be strictly adhered to and checked frequently. All hoses and fittings should be inspected for condition and tightness of connections. Check the drive belt for wear and tension every 12 months or 12,000 miles. REMOVAL & INSTALLATION See Figures 2, 3 and 4 Air Pump CAUTION Do not pry on the pump housing or clamp the pump in a vise; the housing is soft aluminum and may become distorted. 1. Disconnect the negative (-) battery cable and the air hoses at the pump. 2. Hold the pump pulley from turning and loosen the pulley bolts. 3. Loosen the pump mounting bolt and adjustment bracket bolt. Remove the drive belt. 4. Remove the mounting bolts, and then remove the pump. To install: 5. Position the pump into the mounting brackets and loosely install the bolts. 6. Install the drive belt and adjust the tension to 146 ft. lbs. for a new belt and 90 ft. lbs. for an old belt. Torque the mounting bolts to 25 ft. lbs. (34 Nm). 7. Install and reconnect the pump hoses and electrical connections. Fig. Fig. 2: Removing the air pump Pump Filter 1. Remove the drive belt and pump pulley. 2. Using needlenose pliers, pull the fan/filter unit from the pump hub. Use care to prevent any dirt or fragments from entering the air intake hole. DO NOT insert a screwdriver between the pump and the filter, and do not attempt to remove the metal hub. It is seldom possible to remove the filter without destroying it. Fig. Fig. 3: Air pump filter removal 3. To install a new filter, draw it on with the pulley and pulley bolts. Do not hammer or press the filter onto the pump. 4. Draw the filter down evenly by torquing the bolts alternately. Make sure the outer edge of the filter slips into the housing. A slight amount of interference with the housing bore is normal. The new filter may squeal initially until the sealing lip on the pump outer diameter has worn in. Fig. Fig. 4: Common air pump mounting and location Diverter (Anti-Afterburn) Valve 1. Detach the vacuum sensing line and electrical connections from the valve. 2. Remove the other hose(s) from the valve. 3. Unfasten the diverter valve from the elbow or the pump body. To install: 4. Always use a new gasket. Tighten the valve securing bolts to 85 inch lbs. (10 Nm). Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Air Management System See Figures 1 and 2 Print OPERATION The Air Management system is used on 1981 and later vehicles to provide additional oxygen to continue the combustion process after the exhaust gases leave the combustion chamber; it works in much the same way as the AIR system described earlier in this section. Air is injected into either the exhaust port(s), the exhaust manifold(s) or the catalytic converter by an engine driven air pump. The system is in operation at all times and will bypass air only momentarily during deceleration and at high speeds. The bypass function is performed by the air management valve, while the check valve protects the air pump by preventing any backflow of exhaust gases. The AIR system helps to reduce HC and CO contents in the exhaust gases by injecting air into the exhaust ports during cold engine operation. This air injection also helps the catalytic converter to reach the proper temperature quicker during warm-up. When the engine is warm (closed loop), the AIR system injects air into the beds of a three-way converter to lower the HC and CO content in the exhaust. The air management system utilizes the following components: 1. An engine driven air pump 2. Air management valves (Air Control and Air Switching) 3. Air flow and control hoses 4. Check valves 5. A dual-bed, three-way catalytic converter The belt driven, vane type air pump is located at the front of the engine and supplies clean air to the system for purposes already stated. When the engine is cold, the Electronic Control Module (ECM) energizes an air control solenoid. This allows air to blow to the air switching valve. The air switching valve is then energized to direct air into the exhaust ports. When the engine is warm, the ECM de-energizes the air switching valve, thus directing the air between the beds of the catalytic converter. This then provides additional oxygen for the oxidizing catalyst in the second bed to decrease HC and CO levels, while at the same time keeping oxygen levels low in the first bed, enabling the reducing catalyst to effectively decrease the levels of NOx. Fig. Fig. 1: Air management valve If the air control valve detects a rapid increase in manifold vacuum (deceleration), certain operating modes (wide open throttle, etc.) or if the ECM selfdiagnostic system detects any problems in the system, air is diverted to the air cleaner or directly into the atmosphere. The primary purpose of the ECM's divert mode is to prevent backfiring. Throttle closure at the beginning of deceleration will temporarily create air/fuel mixtures which are too rich to burn completely. These mixtures will become burnable when they reach the exhaust if they are combined with injection air. The next firing of the engine will ignite the mixture causing an exhaust backfire. Momentary diverting of the injection air from the exhaust prevents this. The air management system check valves and hoses should be checked periodically for any leaks, cracks or deterioration. Fig. Fig. 2: Check valve and hoses SERVICE This effectiveness depends on correct engine idle speed and ignition timing. These settings should be strictly adhered to and checked frequently. All hoses and fittings should be inspected for condition and tightness of connections. Check the drive belt for wear and tension every 12 months or 12,000 miles. REMOVAL & INSTALLATION Air Pump 1. Disconnect the negative (-) battery cable. Remove the valves and/or adapter at the air pump. 2. Loosen the air pump adjustment bolt and remove the drive belt. 3. Unscrew the three mounting bolts and then remove the pump pulley. 4. Unscrew the pump mounting bolts and then remove the pump. To install: 5. Be sure to adjust the drive belt tension after installing the pump. 6. Install the three mounting bolts and adjust the belt to 146 ft. lbs. for a new belt and 90 ft. lbs. for an old belt. 7. Torque the air pump adjustment bolt to 25 ft. lbs. (34 Nm). 8. Connect the negative (-) battery cable. Install the valves and/or adapter at the air pump. Check Valve 1. Disconnect the negative (-) battery cable. Release the clamp and disconnect the air hoses from the valve. The valve may be seized to the injection pipe due to rust. Soak the fitting with penetrating oil for an hour or two before attempting removal. Always use a backup wrench when attempting to remove the valve. 2. Unscrew the check valve from the air injection pipe. 3. Install the valve and torque to 30 ft. lbs. (41 Nm). Connect all disconnected hoses and negative battery cable. Air Management Valve 1. Disconnect the negative battery cable. 2. Remove the air cleaner. 3. Tag and disconnect the vacuum hose from the valve. 4. Tag and disconnect the air outlet hoses from the valve 5. Bend back the lock tabs and then remove the bolts holding the elbow to the valve. 6. Tag and disconnect any electrical connections at the valve and then remove the valve from the elbow. To install: 7. Install the valve and connect any electrical connections at the valve. 8. Torque the valve bolts to 10 ft. lbs. (14 Nm) and bend back the lock tabs. 9. Connect the air outlet hoses to the valve 10. Connect the vacuum hose to the valve. 11. Install the air cleaner. 12. Connect the negative battery cable. Pump Filter 1. Remove the drive belt and pump pulley. 2. Using needlenose pliers, pull the fan/filter unit from the pump hub. Use care to prevent any dirt or fragments from entering the air intake hole. DO NOT insert a screwdriver between the pump and the filter, and do not attempt to remove the metal hub. It is seldom possible to remove the filter without destroying it. 3. To install a new filter, draw it on with the pulley and pulley bolts. Do not hammer or press the filter onto the pump. 4. Draw the filter down evenly by torquing the bolts alternately. Make sure the outer edge of the filter slips into the housing. A slight amount of interference with the housing bore is normal. The new filter may squeal initially until the sealing lip on the pump outer diameter has worn in. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Catalytic Converter See Figures 1, 2 and 3OPERATION Print The catalytic converter is a muffler-like container built into the exhaust system to aid in the reduction of exhaust emissions. The catalyst element consists of individual pellets or a honeycomb monolithic substrate coated with a metal such as platinum, palladium, rhodium or a combination of these. When the exhaust gases come into contact with the catalyst, a chemical reaction occurs which will reduce the pollutants into harmless substances like water and carbon dioxide. There are essentially two types of catalytic converters: an oxidizing type is used on all 1975-80 models with the exception of those 1980 models built for California. It requires the addition of oxygen to spur the catalyst into reducing the engine's HC and CO emissions into H 2 O and CO 2 . Because of this need for oxygen, the AIR system is used with all these models. Fig. Fig. 1: Bead type catalytic converter The oxidizing catalytic converter, while effectively reducing HC and CO emissions, does nothing in the way of reducing NOx emissions. Thus, the threeway catalytic converter was developed to reduce the NOx emissions. Fig. Fig. 2: Dual bed type catalytic converter The three-way converter, unlike the oxidizing type, is capable of reducing HC, CO and NOx, emissions, all at the same time. In theory, it seems impossible to reduce all three pollutants in one system since the reduction of HC and CO requires the addition of oxygen, while the reduction of NOx calls for the removal of oxygen. In actuality, the three-way system really can reduce all three pollutants, but only if the amount of oxygen in the exhaust system is precisely controlled. Due to this precise oxygen control requirement, the three-way converter system is used only in vehicles equipped with an oxygen sensor system (1980 Calif. vehicles and all 1981 and later models). Fig. Fig. 3: Single bed monolith type converter SERVICE There are no service procedures required for the catalytic converter, although the converter body should be inspected occasionally for damage. Some models with the V6 engine require a catalyst change at 30,000 mile intervals (consult your Owner's Manual). REMOVAL & INSTALLATION Refer to Engine & Engine Overhaul for Removal and Installation procedures. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Controlled Combustion System OPERATION Print The CCS system relies upon leaner air/fuel mixtures and altered ignition timing to improve combustion efficiency. A special air cleaner with a thermostatically controlled opening is used on most CCS equipped models to ensure that air entering the carburetor is kept at 100°F (38°C). This allows leaner carburetor settings and improves engine warm-up. A 15°F higher temperature thermostat is employed on CCS vehicles to further improve emission control. SERVICE Since the only extra component added with a CCS system is the thermostatically controlled air cleaner, there is no additional maintenance required; however, tune-up adjustments such as idle speed, ignition timing, and dwell become much more critical. Care must be taken to ensure that these settings are correct, both for trouble free operation and a low emission level. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Crankcase Ventilation Systems OPERATION Print Gasoline Engines See Figures 1 and 2 All Buick, Oldsmobile, Chevrolet and Pontiac gasoline engines covered in this guide are equipped with a positive crankcase ventilation (PCV) system to control crankcase blow-by vapors. The system functions as follows: When the engine is running, a small portion of the gases which are formed in the combustion chamber leak by the piston rings and enter the crankcase. Since these gases are under pressure, they tend to escape from the crankcase and enter the atmosphere. If these gases are allowed to remain in the crankcase for any period of time, they contaminate the engine oil and cause sludge to build up in the crankcase. If the gases are allowed to escape into the atmosphere, they pollute the air with unburned hydrocarbons. The job of the crankcase emission control equipment is to recycle these gases back into the engine combustion chamber where they are reburned. The crankcase (blow-by) gases are recycled in the following way: as the engine is running, clean, filtered air is drawn through the air filter and into the crankcase. As the air passes through the crankcase, it picks up the combustion gases and carries them out of the crankcase, through the oil separator, through the PCV valve, and into the induction system. As they enter the intake manifold, they are drawn into the combustion chamber where they are reburned. The most critical component in the system is the PCV valve. Located in the valve cover or intake manifold, this valve controls the amount of gases which are recycled into the combustion chamber. At low engine speeds, the valve is partially closed, limiting the flow of the gases into the intake manifold. As engine speed increases, the valve opens to admit greater quantities of the gases into the intake manifold. As engine speed increases, the valve opens to admit greater quantities of the gases into the intake manifold. If the valve should become blocked or plugged, the gases will be prevented from escaping from the crankcase by the normal route. Since these gases are under pressure, they will find their own way out of the crankcase. This alternate route is usually a weak oil seal or gasket in the engine. As the gas escapes by the gasket, it also creates an oil leak. Besides causing oil leaks, a clogged PCV valve also allows these gases to remain in the crankcase for an extended period of time, promoting the formation of sludge in the engine. See Routine Maintenance for PCV valve replacement intervals. Fig. Fig. 1: V6 PCV valve location Fig. Fig. 2: V8 PCV valve location Diesel Engines See Figure 3 A Crankcase Depression Regulator Valve (CDRV) or flow control valve is used to regulate (meter) the flow of crankcase gases back into the engine to be burned. The CDRV is designed to limit vacuum in the crankcase as the gases are drawn from the valve covers through the CDRV and into the intake manifold (air crossover). Fresh air enters the engine through the combination filter, check valve and oil fill cap. The fresh air mixes with blow-by gases and enters both valve covers. The gases pass through a filter installed on the valve covers and are drawn into connecting tubing. Intake manifold vacuum acts against a spring loaded diaphragm to control the flow of crankcase gases. Higher intake vacuum levels pull the diaphragm closer to the top of the outlet tube. This reduces the amount of gases being drawn from the crankcase and decreases the vacuum level in the crankcase. As the intake vacuum decreases, the spring pushes the diaphragm away from the top of the outlet tube allowing more gases to flow to the intake manifold. Fig. Fig. 3: Diesel crankcase ventilation flow SERVICE Gasoline Engines Slow, unstable idling, frequent stalling, oil leaks and oil in the air cleaner are all signs that the PCV valve may be clogged or faulty. Follow the PCV valve testing procedure in Routine Maintenance and replace the valve if necessary. Check the valve at every tune-up. Diesel Engines Do not attempt to test these valves. Instead, follow the cleaning procedures in Routine Maintenance if you are experiencing problems with the system. REMOVAL & INSTALLATION Gasoline Engines 1. To replace the filter, slide the rubber coupling that joins the tube coming from the valve cover to the filter off the filter nipple. Then, remove the top of the air cleaner. Slide the spring clamp off the filter, and remove the filter. 2. Inspect the rubber grommet in the valve cover and the rubber coupling for brittleness and cracking. Replace parts as necessary. 3. Insert the new PCV filter through the hole in the air cleaner with the open portion of the filter upward. Make sure that the square portion of filter behind the nipple fits into the (square) hole in the air cleaner. 4. Install a new spring clamp onto the nipple. Make sure the clamp goes under the ridge on the filter nipple all the way around. Then, reconnect the rubber coupling and install the air cleaner cover. 5. To replace the valve, gently pull the hose from the top of the valve, then pull the valve out of the cover grommet. 6. Installation is the reverse of removal. Diesel Engines The filter assemblies can be removed by carefully prying them from the valve covers. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide ENGINE EMISSION CONTROLS In its normal operation, the internal combustion engine releases several compounds into the atmosphere. Since most of these compounds are harmful to our health if inhaled or ingested for long periods (and in sufficient quantity), the Federal Government has placed a limit on the quantities of the three main groups of compounds: unburned hydrocarbons (HC); carbon monoxide (CO); and oxides of nitrogen (NOx). Print The emissions systems covered in this section are designed to regulate the output of these fumes by your vehicle's engine and fuel system. Three areas of the automobile are covered, each with its own anti-pollution system or systems; the engine crankcase, which emits unburned hydrocarbons in the form of oil and fuel vapors; the fuel storage system (fuel tank and carburetor), which also emits unburned hydrocarbons in the form of evaporated gasoline; and the engine exhaust. Exhaust emissions comprise the greatest quantity of auto emissions, in the forms of unburned hydrocarbons, carbon monoxide, and oxides of nitrogen. Because of this, there are more pollution devices on your vehicle dealing with exhaust emissions than there are dealing with the other two emission types. Exhaust emission controls comprise the largest body of emission controls installed on your vehicle. Included in this category are: Thermostatic Air Cleaner (THERMAC) Air Injection Reactor System (A.I.R., 1975-80) Air Management System (1981 and later) Early Fuel Evaporation system (EFE) Exhaust Gas Recirculation Controlled Combustion System (CCS) Computer Controlled Catalytic Converter system (C-4) Computer Command Control (CCC) Mixture Control Solenoid (M/C) Throttle Position Sensor (TPS) Idle Speed Control (ISC) Electronic Spark Timing (EST) Electronic Spark Control (ESC) Transmission Converter Clutch (TCC) Catalytic Converter and the Oxygen Sensor system A brief description of each system and any applicable service procedures follows. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Early Fuel Evaporation (EFE) System See Figures 1, 2 and 3 Print OPERATION Two types of EFE have been used on the engines covered in this guide. Both provide quick heat to the induction system. This helps evaporate fuel (allowing the choke to close faster and thus reducing emissions) when the engine is cold. It also aids cold driveability. The vacuum servo EFE system uses a valve between the exhaust manifold and exhaust pipe, operated by vacuum and controlled by either a thermal vacuum valve or electric solenoid. The valve causes hot exhaust gas to enter the intake manifold heat riser passages, heating the incoming fuel mixture. The electrically heated type EFE uses a ceramic heater plate located under the carburetor, controlled through the ECM. The vacuum type EFE should be checked for proper operation at every tune-up. On 1981 and later V6 engines, the EFE system is controlled by the ECM. COMPONENT TESTING Vacuum type 1. Locate the EFE valve on the exhaust manifold and not the position of the actuator arm. On some vehicles, the valve and arm are covered by a twopiece cover which must be removed for access. Make sure the engine is overnight cold. 2. Watch the actuator arm when the engine is started. The valve should close when the engine is started cold; the actuator link will be pulled into the diaphragm housing. 3. If the valve does not close, stop the engine. Remove the hose from the EFE valve and apply 10 in. Hg of vacuum by hand pump. The valve should close and stay closed for at least 20 seconds (you will hear it close). If the valve opens in less than 20 seconds, replace it. The valve could also be seized if it does not close; lubricate it with spray type manifold heat valve lube. If the valve does not close when vacuum is applied and when it is lubricated, replace the valve. 4. If the valve closes, the problem is not with the valve. Check for loose, cracked, pinched or plugged hoses, and replace as necessary. Test the EFE solenoid (located on the valve cover bracket); if it is working, the solenoid plunger will emit a noise when the current is applied. 5. Warm up the engine to operating temperature. 6. Watch the EFE valve to see if it has opened. It should now be open. If the valve is still closed, replace the solenoid if faulty, and/or check the engine thermostat; the engine coolant may not be reaching normal operating temperature. Fig. Fig. 1: Vacuum-servo type EFE system Electric type 1. To test the EFE heater, turn the ignition OFF and disconnect the electrical connector. 2. Using an ohmmeter, check the resistance between the two terminals of the heater connector. 3. If resistance is under two ohms, the heater is good. If not, replace the heater. Fig. Fig. 2: Electric-type EFE system REMOVAL & INSTALLATION Vacuum type EFE valve If the vehicle is equipped with an oxygen sensor, it is located near the EFE valve. Use care when removing the EFE valve as not to damage the oxygen sensor. 1. Disconnect the negative (-) battery cable and vacuum hose at the EFE valve. 2. Remove the exhaust pipe-to-manifold nuts, and the washers and tension springs if used. 3. Lower the exhaust cross-over pipe. On some models, complete removal of the pipe is not necessary. 4. Remove the EFE valve. To install: 5. Always install new seals and gaskets. 6. Torque the exhaust nuts to 22 ft. lbs. (30 Nm). 7. Connect the negative battery cable and vacuum hose to the valve. Electric type EFE 1. Remove the air cleaner. 2. Disconnect all vacuum, electrical and fuel connections from the carburetor. 3. Disconnect the EFE heater electrical connector. 4. Remove the carburetor. 5. Remove the EFE heater insulator (plate) assembly. 6. Installation is the reverse of removal. EFE Solenoid 1. Disconnect the battery ground. 2. Remove the air cleaner assembly if necessary. 3. Disconnect and tag all electrical and vacuum hoses as required. 4. Remove the screw securing the solenoid to the valve cover bracket and remove the solenoid. 5. Installation is reverse of removal. Thermal Vacuum Switch (TVS) 1. Disconnect the negative (-) battery cable. 2. Remove the air cleaner. 3. Partially drain the engine coolant. 4. Remove the hoses from the TVS assembly located in the engine coolant outlet housing or at the rear of the intake manifold. Remove the switch from the engine. To install: 5. Refer to the number stamped on the base of the TVS for calibration temperature. 6. Apply a soft setting pipe sealant to the switch threads. 7. Install the switch and torque to 120 inch lbs. (14 Nm). Reconnect the vacuum hoses and negative battery cable. 8. Install the air cleaner assembly. Fig. Fig. 3: TVS switch used on some EFE systems Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Evaporative Emission Control System See Figures 1, 2, 3, 4 and 5 Print OPERATION This system reduces the amount of escaping gasoline vapors. Float bowl emissions are controlled by internal carburetor modifications. Redesigned bowl vents, reduced bowl capacity, heat shields, and improved intake manifold-to-carburetor insulation reduce vapor loss into the atmosphere. The venting of fuel tank vapors into the air has been stopped by means of the carbon canister storage method. This method transfers fuel vapors to an activated carbon storage device which absorbs and stores the vapor that is emitted from the engine's induction system while the engine is not running. When the engine is running, the stored vapor is purged from the carbon storage device by the intake air flow and then consumed in the normal combustion process. As the manifold vacuum reaches a certain point, it opens a purge control valve atop the charcoal storage canister. This allows air to be drawn into the canister, thus forcing the existing fuel vapors back into the engine to be burned normally. On 1981 and later V6s, the purge function is electronically controlled by a purge solenoid in the line which is itself controlled by the Electronic Control Module (ECM). When the system is in the Open Loop mode, the solenoid valve is energized, blocking all vacuum to the purge valve. When the system is in the Closed Loop mode, the solenoid is de-energized, thus allowing existing vacuum to operate the purge valve. This releases the trapped fuel vapor and it is forced into the induction system. Fig. Fig. 1: Canister Control Valve (CCV) Some canister systems (those without a vapor vent valve) starting in 1981 have a Canister Control Valve (C.C.V.). This is mounted near the carburetor and has four hoses connected to it. When the engine is off, manifold vacuum is non-existent at the C.C.V. and a spring loaded valve in the C.C.V. interconnects the carburetor vent hose to the canister via a Thermostatic Vacuum Valve which opens at 170°F (77°C). Vapors generated in the carburetor float bowl thus pass into the canister. When the engine is restarted, this valve closes as manifold vacuum is applied to it. When the TVS is open, the canister is purged as fuel vapors are drawn out of the canister and into the carburetor throttle body. Most carbon canisters used are of the open design, which means that the incoming air is drawn directly from the air cleaner. Fig. Fig. 2: Open canister evaporative emission control system (EECS). This system is more common than the closed system Fig. Fig. 3: Closed canister EECS Fig. Fig. 4: Common EECS canister Fig. Fig. 5: This model has a TVS located on the air cleaner SERVICE The only service required for the evaporative emissions system is the periodic replacement of the charcoal canister filter. Closed canisters do not require that this operation be performed. If the fuel tank cap on your vehicle ever requires replacement, make sure that it is of the same type as the original. REMOVAL & INSTALLATION 1. Tag and disconnect all hoses. 2. Loosen the retainer clamps and lift out the canister. 3. Grasp the filter element and pull it out. 4. Replace the filter, then place the canister in the clamps and reconnect all hoses. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Exhaust Gas Recirculation (EGR) System OPERATION Print Gasoline Engines See Figures 1, 2 and 3 All engines covered in this guide are equipped with exhaust gas recirculation (EGR). This system consists of a metering valve, a vacuum line to the carburetor, and cast-in exhaust gas passages in the intake manifold. The EGR valve is controlled by carburetor vacuum, and accordingly opens and closes to admit exhaust gases into the fuel/air mixture. The exhaust gases lower the combustion temperature, and reduce the amount of oxides of nitrogen (NOx) produced. The valve is closed at idle between the two extreme throttle positions. In most installations, vacuum to the EGR valve is controlled by a thermal vacuum switch (TVS); the switch, which is installed into the engine block, shuts off vacuum to the EGR valve until the engine is hot. This prevents the stalling and rough idle which would result if EGR occurred when the engine was cold. As the vehicle accelerates, the carburetor throttle plate uncovers the vacuum port for the EGR valve. At 3-5 in. Hg, the EGR valve opens and then some of the exhaust gases are allowed to flow into the air/fuel mixture to lower the combustion temperature. At full throttle the valve closes again.Some California engines are equipped with a dual diaphragm EGR valve. This valve further limits the exhaust gas opening (compared to the single diaphragm EGR valve) during high intake manifold vacuum periods, such as high speed cruising, and provides more exhaust gas recirculation during acceleration when manifold vacuum is low. In addition to the hose running to the thermal vacuum switch, a second hose is connected directly to the intake manifold. Fig. Fig. 1: EGR valve location For 1977, all California models and vehicles delivered in areas above 4000 feet are equipped with back pressure EGR valves. This valve is also used on all 1978-81 models. The EGR valve receives exhaust back pressure through its hollow shaft. This exerts a force on the bottom of the control valve diaphragm, opposed by a light spring. Under low exhaust pressure (low engine load and partial throttle), the EGR signal is reduced by an air bleed. Under conditions of high exhaust pressure (high engine load and large throttle opening), the air bleed is closed and the EGR valve responds to an unmodified vacuum signal. At wide open throttle, the EGR flow is reduced in proportion to the amount of vacuum signal available. Fig. Fig. 2: Positive backpressure EGR valve 1979 and later models have a ported signal vacuum EGR valve. The valve opening is controlled by the amount of vacuum obtained from a ported vacuum source on the carburetor and the amount of backpressure in the exhaust system. Some late model vehicles with V6 and V8 engines use EGR Vacuum Control. This system uses a solenoid controlled by the Electronic Control Module to control vacuum going to the EGR valve. The ECM evaluates a number of engine parameters to determine EGR requirements, and then opens and closes the solenoid many times a second to produce the required vacuum. The length of each open cycle is increased to transmit increased vacuum. Fig. Fig. 3: Solenoid controlled EGR valve system Diesel Engines The diesel EGR systems work in the same basic manner as the gasoline engines. There are two systems used on the V8 diesels. One is used on the B-body station wagons and the other type is used on all other models. On the B-body type EGR, vacuum from a vacuum pump is modulated by the Vacuum Regulator Valve (VRV) mounted on the injection pump. Vacuum is highest at idle and decreases to zero at wide open throttle. A Response Vacuum Reducer Valve is used between the VRV and the EGR valve to allow the EGR to change position quickly as throttle position is changed. On all other V8 diesels, the EGR system is the same as used on the B-body system, except a solenoid is added to the system that shuts off vacuum to the EGR valve when the Torque Converter Clutch is engaged. This solenoid is fed 12V from the TCC switch portion of the VRV and is grounded through the transmission's governor pressure switch. COMPONENT TESTING Gasoline Engines To check the EGR valve operation, check with a mirror under the valve to see if the valve moves when the throttle is opened. If the diaphragm does not move, there is either a problem with vacuum or the valve is stuck. With the valve stuck open, the engine will run very rough at idle or may not even start. If it is stuck closed, you would likely experience severe pinging when the engine is under load or on acceleration. With a vacuum gauge hooked up at the EGR vacuum line, you should see vacuum on the gauge when the throttle is opened. To find out if the exhaust gas is actually recirculating, use a hand vacuum pump to open the EGR valve with the engine idling. If the engine runs rough or stalls, the exhaust gas is recirculating. If it does not, remove the EGR valve and clean it as well as the EGR ports in the intake manifold. When testing with a hand vacuum pump, EGR valves should hold a steady vacuum and not leak. If they do leak, they must be replaced. The newer back-pressure type EGR valves cannot be tested with a vacuum pump. The only practical way to test these valves is by substitution of a known good valve. Diesel Engines See Figure 4 VACUUM REGULATOR VALVE (VRV) The Vacuum Regulator Valve is attached to the side of the injection pump and regulates vacuum in proportion to throttle angle. Vacuum from the vacuum pump is supplied to port A and vacuum at port B is reduced as the throttle is opened. At closed throttle, the vacuum is 15 in. Hg; at half throttle, 6 in. Hg; at wide open throttle there is zero vacuum. Fig. Fig. 4: Vacuum regulator valve EXHAUST GAS RECIRCULATION (EGR) VALVE See Figure 5 Apply vacuum to vacuum port. The valve should be fully open at 10.5 in. Hg and closed below 6 in. Hg on 1984 and earlier models. On 1985 models, the valve should be wide open at 21 in. Hg and closed below 6 in. Hg. Fig. Fig. 5: Diesel EGR valve RESPONSE VACUUM REDUCER (RVR) See Figure 6 Connect a vacuum gauge to the port marked To EGR valve or T.C.C. solenoid. Connect a hand operated vacuum pump to the VRV port. Draw a 50.66 kPa (15 in. Hg) vacuum on the pump and the reading on the vacuum gauge should be lower than the vacuum pump reading. Models up to 1983: 0.75 in. Hg Except High Altitude; 2.5 in. Hg High Altitude. 1984 Models: 2 in. Hg. Fig. Fig. 6: Diesel EGR vacuum reducer TORQUE CONVERTER CLUTCH OPERATED SOLENOID When the torque converter clutch is engaged, an electrical signal energizes the solenoid allowing ports 1 and 2 to be interconnected. When the solenoid is not energized, port 1 is closed and ports 2 and 3 are interconnected. Specific operation is listed below. Models up to 1983: Solenoid Energized - Ports 1 and 3 are connected Solenoid De-energized - Ports 2 and 3 are connected 1984 Models: Solenoid Energized - Ports 1 and 2 are connected Solenoid De-energized - Ports 2 and 3 are connected QUICK VACUUM RESPONSE VALVE See Figure 7 Tee a vacuum gauge into the line running from this valve to the Exhaust Pressure Regulator (EPR) valve, which is located on the bottom of the exhaust manifold. Disconnect the hose that runs from the inlet port S and connect a hand vacuum pump to the open end of the hose. Draw a vacuum of 22 in. Hg at the pump. The gauge located at the outlet side should read 20.7 in. Hg within two seconds. Reduce the vacuum coming from the pump to 0.9 in. Hg. The vacuum gauge should read the same within half a second. Fig. Fig. 7: Quick Vacuum Response Valve EGR-TVS (1984-85 MODELS) See Figure 8 1. Drain coolant from the engine until the level is below the EGR-TVS. Then, remove the valve from the engine by disconnecting all vacuum lines and electrical leads and unscrewing it with a wrench on the flats. CAUTION When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. 2. Inspect the valve for any visible defects and replace it if any are visible. Allow the valve to cool to room temperature. 3. Connect a vacuum gauge to port 2 and hand operated vacuum pump to port 4. 4. Connect a self-powered test lamp across the switch terminals. 5. Immerse just the bottom (threaded portion) of the valve in a pan of cool water. Put a thermometer in the water and then heat the water slowly as you pull vacuum and watch the vacuum gauge and also watch the test lamp. The two functions of the switch should respond as specified below: Vacuum: Port 2 and 3 should become connected and Port 1 should become blocked as the temperature passes 100°F plus or minus 3.6° (38°C). Electrical: The contacts should open at 107°F plus or minus 3.6° (42°C). 6. Now remove the water from heat, watch the temperature, and check for an appropriate response as the temperature falls: Vacuum: Port 2 and 1 should be connected and port 3 blocked as the temperature falls below 89°F plus or minus 3.6° (32°C). Electrical: The contacts should close at 89°F plus or minus 3.6° (32°C). 7. If any of the tests are failed, the valve must be replaced. Coat the threads of the old or replacement valve with sealer and install it. Make all vacuum and electrical connections, replace water/antifreeze mix, operate the engine until hot and check for leaks. Fig. Fig. 8: EGR-TVS used on 1984 and later models REMOVAL & INSTALLATION Gasoline and Diesel Engines See Figures 9, 10 and 11 1. Detach the vacuum lines from the EGR valve. 2. Unfasten the two bolts or bolt and clamp which attach the valve to the manifold. Withdraw the valve. To install: 3. Clean the valve and intake manifold. For valves that protrude from the mounting face, hold the valve assembly in hand, tap the valve lightly with a small plastic hammer to remove exhaust deposits from the valve seat. Shake out any loose particles. DO NOT put the valve in a vise. Carefully remove any exhaust deposits from the mounting surface of the valve with a wire wheel or putty knife. Do not damage the mounting surface. Depress the valve diaphragm and inspect the valve seating area through the valve outlet for cleanliness. If the valve and/or seat are not completely clean, repeat procedure. Look for exhaust deposits in the valve outlet, and remove any deposits with a suitable cleaning tool. For valves that do not protrude, clean the base of the valve with a wire brush or wheel to remove exhaust deposits from the mounting surface. Clean the valve seat and valve in an abrasive-type spark plug cleaning machine or sandblaster. Most machine shops provide this service. Make sure the valve portion is cleaned (blasted) for about 30 seconds, and that the valve is also cleaned with the diaphragm spring fully compressed (valve unseated). The cleaning should be repeated until all deposits are removed. The valve must be blown out with compressed air thoroughly to ensure all abrasive material is removed from the valve. CAUTION DO NOT wash the valve assembly in solvents or degreasers; permanent damage to the valve diaphragm may result. 4. Clean the mounting surface of the intake manifold. 5. With the valve removed, start the engine for two seconds to blow out the loose carbon deposits. To install: 6. Clean the mounting surfaces of the intake manifold and valve assembly. Always use a new gasket between the valve and the manifold. Torque the retaining bolts or nuts to 15 ft. lbs. (20 Nm). On dual diaphragm valves, attach the carburetor vacuum line to the tube at the top of the valve, and the manifold vacuum line to the tube at the center of the valve. Fig. Fig. 9: After you disconnect the vacuum hose, be sure to label it Fig. Fig. 10: On some EGR valves you must pry the lock-tab away from the bolt Fig. Fig. 11: Removing the EGR valve from the engine Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Service Flags RESETTING Print Vehicles equipped with the C-4 system have an emission indicator flag which will appear in the odometer window when service is necessary. The flags are marked SENSOR, EMISSION, and CATALYST, depending on the device that is scheduled for regular maintenance. To reset the flag, first remove the instrument panel trim plate and cluster cover lens. There are reset notches on the drivers side of the indicator flag. Insert a long, pointed probe diagonally into the detents on the upper left side and rotate the flag downward until an alignment mark becomes visible in the left side of the odometer window. Once the flag has been reset, replace the cluster lens and trim plate. C-4 and CCC vehicles are equipped with a Service Engine Soon or Check Engine light. This light is on the instrument panel below the fuel gauge. The light will come ON during engine start-up to let you know the bulb is working. Have the system checked by your dealer if the light does not come on during start-up or if the light illuminates intermittently or continuously while driving. These conditions may indicate that the Computer Command Control system is in need of service. In most cases, the vehicle will not have to be towed, but the vehicle should be serviced as soon as possible. For more information about the service light, refer to Computer Command Control section in this section. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Thermostatic Air Cleaner (THERMAC) OPERATION Print See Figures 1 and 2 All engines covered in this guide utilize the THERMAC system (in 1978 it was called TAC, but was the same). This system is designed to warm the air entering the carburetor when underhood temperatures are low, and to maintain a controlled air temperature into the carburetor at all times. By allowing preheated air to enter the carburetor, the amount of time the choke is on is reduced, resulting in better fuel economy and lower emissions. Engine warmup time is also reduced. Fig. Fig. 1: THERMAC air cleaner The Thermac system is composed of the air cleaner body, a filter, sensor unit, vacuum diaphragm, damper door, and associated hoses and connections. Heat radiating from the exhaust manifold is trapped by a heat stove and is ducted to the air cleaner to supply heated air to the carburetor. A movable door in the air cleaner case snorkel allows air to be drawn in from the heat stove (cold operation) or from underhood air (warm operation). The door position is controlled by the vacuum motor, which receives intake manifold vacuum as modulated by the temperature sensor. Fig. Fig. 2: Vacuum motor positions COMPONENT TESTING 1. Check the vacuum hoses for leaks, kinks, breaks, or improper connections and correct any defects. 2. With the engine off, check the position of the damper door within the snorkel. A mirror can be used to make this job easier. The damper door should be open to admit outside air. 3. Apply at least 7 in. Hg of vacuum to the damper diaphragm unit. The door should close. If it does not, check the diaphragm linkage for binding and correct hookup. 4. With vacuum still applied and the door closed, clamp the tube to trap the vacuum. If the door does not remain closed, there is a leak in the diaphragm assembly. 5. If the diaphragm is holding vacuum and the system has source vacuum, the last choose is the air bleed valve located in the air cleaner assembly. 6. The air bleed may be holding the damper door closed even after the vehicle has warmed up. Or the valve may not close the door at all. In any case, if the damper diaphragm and vacuum source are OK, replace the air bleed valve. REMOVAL & INSTALLATION See Figures 3, 4, 5, 6 and 7 Vacuum Motor 1. Remove the air cleaner and the vacuum hose from the motor. 2. Drill out the two spot welds and remove the retaining strap. 3. Lift up motor, cocking it to one side to unhook the motor linkage at the control damper assembly. 4. Install the vacuum motor linkage into the control damper assembly. 5. Use a sheet metal screw to resecure the motor retaining strap. 6. Reinstall the vacuum hose and the air cleaner. Sensor 1. Remove the air cleaner and vacuum hoses. 2. Pry up the tabs on the sensor retaining clip. Remove the clip and the sensor from the air cleaner. Note the position of sensor for installation. 3. Install the sensor and gasket in original position. 4. Install vacuum hoses and air cleaner. Fig. Fig. 3: Remove the air cleaner cover and element Fig. Fig. 4: On some models, the air intake hose is retained by small lock tabs Fig. Fig. 5: Be sure to label all vacuum hoses when disconnecting them Fig. Fig. 6: To remove any other sensors or switches from the side of the air cleaner, simply pull the retaining clip out Fig. Fig. 7: The Thermac sensor is located on the bottom of the air cleaner. Pry the retaining off to remove the sensor Back to Top Fuel System GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Description of System See Figure 1 Print This is a throttle body fuel injection system with two fuel injectors mounted at the top of the throttle body, which spray fuel down through the throttle valves and into the intake manifold. The throttle body resembles a carburetor in appearance but does away with much of the complexity (choke system, power valves, accelerator pump, fuel circuits, etc.), replacing them with an electronically operated fuel injector. The injector is actually a solenoid which when activated, lifts a pintle off it's seat, allowing the pressurized fuel behind the valve to spray out. The nozzle of the injector is designed to atomize the fuel for a complete air/fuel mixture. The activating signal for the injector originates with the Electronic Control Module (ECM), which monitors engine temperature, throttle position, vehicle speed and several other engine-related conditions. The ECM continuously updates the injector opening times in relation to the information given by these sensors. Fuel pressure for the system is provided by an in-tank fuel pump. The pump is designed to provide fuel at about 18 psi (125 kPa). A fuel pressure regulator in the TBI unit keeps fuel available to the injectors at a constant pressure between 9-13 psi (62-90 kPa). Fuel in excess of injector needs is returned to the fuel tank by a separate line. Fig. Fig. 1: TBI operation Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Electric Fuel Pump See Figure 1 Print REMOVAL & INSTALLATION 1. Allow the fuel pressure to bleed off. 2. Disconnect the negative battery cable. 3. Raise the rear of the car and support it with jackstands. Make sure to block the front wheels. 4. Remove the fuel tank. Pleaser refer to the Fuel Tank procedure found later in this section. 5. Remove the fuel lever sending unit and pump assembly by turning the cam lock ring counterclockwise. Lift the assembly from the fuel tank and remove the fuel pump from the fuel lever sending unit 6. Pull the pump up into the attaching hose while pulling outward away from the bottom support. Take care to prevent damage to the rubber insulator and strainer during removal. After pump assembly is clear of the bottom support, pull pump assembly out of the rubber connector for removal. To install: 7. Inspect the pump attaching hose for any signs of deterioration. Replace as necessary. Also check the rubber sound insulator at the bottom of the pump; replace if required. 8. Push fuel pump assembly into the attaching hose. 9. Install the fuel lever sending unit and pump assembly into the tank assembly. Use new O-ring during reassembly. Care should be taken not to fold over or twist the strainer when installing the sending unit as this will restrict fuel flow. 10. Install the cam lock over the assembly and lock by turning clockwise. 11. Reverse fuel tank removal procedure to finish installing. Fig. Fig. 1: In-tank fuel pump TESTING Flow Test 1. Allow the fuel pressure to bleed off. 2. Disconnect the fuel feed line and install a hose on the line. 3. Apply battery voltage (using a fused jumper wire) to terminal "G" of the Assembly Line Date Link (ALDL) connector located under the dash. Terminal "G" is the first terminal on the left of the bottom row. 4. The fuel pump should supply 1 / 2 pint or more in 15 seconds. Pressure Test 1. Allow the fuel pressure to bleed off. 2. Obtain two sections 3 / 8 in. steel tubing. Each should be about 10 in. (254mm) long. Double-flare one end of each section. 3. Install a flare nut on each section. Connect each of the above sections of tubing into the "flare nut-to-flare nut adapters" that are included in the J29658-82 Gage Adapters. 4. Attach the pipe and adapter assemblies to the J-29658 gage. 5. Using proper procedures, raise and support the front of the car. 6. Disconnect the front fuel feed hose from the fuel pipe on the body. 7. Install the 10 in. (254 mm) length of 3 / 8 in. fuel hose onto the fuel feed pipe on the body. Attach the other end of the hose onto one of the sections of pipe mentioned earlier. Secure the hose connections with clamps. 8. Attach the front fuel feed hose onto the other section of tubing. Secure the hose connection with a clamp. 9. Start the engine and check for leaks. 10. Observe the fuel pressure reading. It should be 9-13 psi (62-90 kPa). Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Fuel Pressure Regulator See Figure 1 Print REMOVAL & INSTALLATION The fuel meter cover contains the pressure regulator and is only serviced as a complete preset assembly. CAUTION DO NOT remove the four screws securing the pressure regulator to the fuel meter cover. The pressure regulator includes a large spring under heavy compression which could cause injury if released. Fig. Fig. 1: Fuel meter cover and pressure regulator assembly Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Idle Air Control Valve See Figure 1 Print REMOVAL & INSTALLATION 1. Remove the air cleaner and disconnect the IAC valve electrical connection. 2. Remove the valve using a 1 1 / 4 in. (32mm) wrench on the hex surface only. To install: 3. Before installing the new valve, measure from motor housing to the end of the cone. Distance should be no greater than 1 1 / 8 in. (28 mm). If necessary, reduce the distance. On Type 1 valves exert firm pressure on the valve to retract it. On Type 2 valves, compress the retaining spring while turning valve in with a clockwise motion. 4. Install the new idle air control valve to the throttle body; use a new gasket. 5. Reconnect the electrical connector and install the air cleaner. 6. Start engine and allow it to reach operating temperature. The ECM will reset idle speed when the vehicle is driven above 35 mph (56 kph). Fig. Fig. 1: IAC valve identification Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Relieving Fuel System Pressure This system incorporates a bleed in the pressure regulator which automatically relieves pressure any time the engine is turned off, but a small amount of fuel may be released when the fuel line is disconnected. To reduce the chance of personal injury, cover the fuel line with a shop cloth to collect the fuel, and then place the cloth in an approved container. Print Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Throttle Body See Figures 1, 2 and 3 REMOVAL & INSTALLATION Print 1. Allow the fuel pressure to bleed off. 2. Disconnect the negative battery cable. 3. Remove the air cleaner assembly, noting and labeling the vacuum and electrical connections. 4. Disconnect and label the electrical connectors at the TBI unit. 5. Disconnect the throttle cable at the TBI unit. 6. Disconnect the fuel feed and return lines. 7. Unbolt and remove the TBI unit. 8. Installation is the reverse of removal. Fig. Fig. 1: TBI unit INJECTOR REPLACEMENT 1. Allow the fuel pressure to bleed off and disconnect the negative battery cable. 2. Remove the air cleaner assembly. 3. Squeeze the two tabs of the injector connector and pull straight up. 4. Remove the fuel meter cover. 5. With the fuel meter cover gasket in place to prevent damage to the casting, use a screwdriver to lift the injector carefully until it is free from the fuel meter body. Fig. Fig. 2: Removing fuel injector 6. Remove the small O-ring from the nozzle end of the injector. Carefully rotate the injector back and forth and remove the filter from the base of the injector. 7. Remove and discard the fuel meter cover gasket. 8. Remove the large O-ring and steel back-up washer from the top of the counterbore of the fuel meter body injector cavity. To install: 9. Install the fuel injector nozzle filter on the nozzle end of the fuel injector. Use a twisting motion to position the filter against the base of the injector. 10. Lubricate a new small O-ring with automatic transmission fluid. Push the O-ring on the nozzle end of the injector until it presses against the injector fuel filter. 11. Install the steel backup washer in the top counterbore of the fuel meter body injector cavity. 12. Lubricate a new large O-ring with automatic transmission fluid and install it directly over the backup washer. Be sure the O-ring is seated properly in the cavity and is flush with the top of the fuel meter casting surface. 13. Install the injector in the cavity, aligning the raised lug on the injector base with the cast-in notch in the fuel meter body cavity. Push down on the injector until it is fully seated in the cavity. 14. Install the fuel meter cover. Thread locking compound must be used on the threads. 15. Install the injector electrical connector. 16. Install the air cleaner and reconnect the negative battery cable. Fig. Fig. 3: Fuel injector components Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Throttle Position Sensor REMOVAL & INSTALLATION Print 1. Remove the air cleaner and disconnect the TPS electrical connector. 2. Remove the two attaching screws, washers and retainers. 3. Remove the sensor. To install: 4. With the throttle valve in the normal closed idle position, install the TPS on the throttle body assembly. Make sure the TPS pickup lever is located ABOVE the tang on the throttle actuator lever. 5. Install the two attaching screws, washers and retainers. Use a thread locking compound on the threads. 6. Reconnect the electrical connector and install the air cleaner. Back to Top Chassis Electrical GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Blower Motor See Figures 1, 2, 3 and 4 Print REMOVAL & INSTALLATION Buick 1975 AND 1976 1. Disconnect the negative battery cable. Support the hood and loosen the hood hinge from the extension and plate assembly. 2. Remove the extension and plate assembly. 3. Disconnect the blower motor wire. 4. Remove the blower motor attaching screws and motor. Oldsmobile and Pontiac 1975 AND 1976 1. Raise the front of the vehicle, support with jackstands and remove the right front wheel. 2. Cut an access hole along the stamped outline on the right fender skirt, using an air chisel or electric hand sabre saw. 3. Disconnect the blower power wire. 4. Remove the blower. To install: 5. Install the blower with the fan, tighten the mounting screws, connect the motor wiring and covering the access hole with a metal plate secured with sealer and sheet metal screws if a hole was cut. 6. Connect the negative battery cable and check for proper operation. Fig. Fig. 1: Blower motor and heater module without A/C; all models similar Fig. Fig. 2: Blower motor and heater module with A/C; all models similar All Models 1977 TO 1990 1. Disconnect the negative battery cable, the blower motor feed wire and the ground wire. 2. Remove the blower motor retaining screws and remove the motor. To install: 3. Use sealer as needed to make a watertight seal, position the motor/fan into the heater module, tighten the mounting screws, connect the motor wiring and negative battery cable and check for proper operation. Fig. Fig. 3: Disconnecting the electrical connections for blower motor removal Fig. Fig. 4: Removing the blower motor from the heater module Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Blower Switch REMOVAL & INSTALLATION Print 1. Remove the control panel. 2. Disconnect the electrical connector. 3. Remove the switch screws and the switch. 4. Installation is the reverse of removal. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Control Panel REMOVAL & INSTALLATION Print See Figure 1 1. Disconnect the negative battery cable. 2. Remove the center instrument panel trim. On some models, screws for this panel are covered by the left and right panel trims. If screws are hidden, first remove those panels on either side of the center panel; then remove the center panel. 3. Slide all controls all the way to the left. Mark the routing of each cable to each damper lever. Then, unscrew the cable clip attaching screws from the heater case until the cable housing can be freed and the cable can be unhooked from the damper lever; then, free the cable and unhook the damper. 4. Remove the screws from the control face. Then, pull the face outward until you can gain access to the electrical and/or vacuum connectors. Disconnect all electrical and vacuum connections. Remove the control head, pulling the cables out through the hole in the dash. To install: 5. Feed the cables through the hole in the dash and locate the head so the vacuum and electrical connections can be made. Connect vacuum and/or electrical connectors. 6. Install the mounting screws for the head. Then, connect the cables. Adjust each so that its damper is forced all the way closed or open, depending on its position. 7. Install the trim panels and moldings in reverse order of their removal. Fig. Fig. 1: Control panel installation; all models similar CABLE ADJUSTMENT See Figure 2 To adjust the vent cable, adjust the turnbuckle at the heater end of the cable so the shut-off valve is firmly seated with the selector lever in the heater position. This adjusts the shut-off valve for both the heater and vent modes. The center, left and right vent valve cables are not adjustable. To adjust the defrost or temperature cables: 1. Slide the clip at the heater end of the cable away from the end of the cable. 2. Move the levers at the control to full "HOT" or "DEFROST" position. This adjusts the cables for proper operation of the valves. Fig. Fig. 2: Control cable attachments at the control head Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Heater Core REMOVAL & INSTALLATION Print See Figures 1, 2, 3, 4, 5, 6, 7, 8, 9 Models Without A/C 1975 AND 1976 1. Disconnect the negative battery cable. Drain the radiator and disconnect the heater inlet and outlet hoses at the dash. Be careful not to damage the heater core if the hoses are stuck onto the core. 2. Disconnect the control wires from the defroster door and vacuum hose diverter door actuator, and the control cable from the temperature door lever. 3. Remove the 4 nuts securing the heater assembly to the firewall. 4. Remove the screw securing the defroster outlet tab to the heater assembly. 5. Remove the heater from the vehicle. To install: 6. Make sure the heater assembly seal is in good condition. 7. Position the assembly onto the dash and tighten the retaining screws. 8. Reconnect the heater hoses, electrical connectors and negative battery cable. Refill the engine with coolant, start the vehicle and check for coolant leaks. 1977 TO 1981 1. Disconnect the negative battery cable and drain the cooling system. 2. Remove the heater hoses from the core tubes. 3. Disconnect the electrical connections. 4. Remove the front module cover screws, and remove the module assembly. 5. Remove the heater core from the module. To install: 6. Make sure the heater assembly seal is in good condition. 7. Position the assembly onto the dash and tighten the retaining screws. 8. Reconnect the heater hoses, electrical connectors and negative battery cable. Refill the engine with coolant, start the vehicle and check for coolant leaks. 1982 AND 1983 1. Disconnect the negative battery cable and the Hoses from the core tubes. Plug them to avoid coolant loss. 2. On the engine side of the firewall, remove the heater core cover from the case. 3. Remove the core bracket and ground screw. 4. Lift out the core. To install: 5. Make sure the heater assembly seal is in good condition. 6. Position the assembly onto the dash and tighten the retaining screws. 7. Reconnect the heater hoses, electrical connectors and negative battery cable. Refill the engine with coolant, start the vehicle and check for coolant leaks. 1984 AND LATER 1. Disconnect the negative battery cable, heater blower resistor wires and blower wires. Disconnect the heater core ground strap at the dash panel. 2. Drain the cooling system and then disconnect both heater hoses at the heater. 3. Remove the seven screws attaching the heater/blower case to the plenum and remove the heater/blower base. 4. Remove the four screws from the heater core shroud, and then remove the shroud and core assembly. 5. Separate the core from the shroud by removing the three screws and core mounting clamps and then separating the two. To install: 6. Using sealer as necessary to prevent leaks at all joints and flanges. 7. Position the assembly onto the dash and tighten the retaining screws. 8. Reconnect the heater hoses, electrical connectors and negative battery cable. Refill the engine with coolant, start the vehicle and check for coolant leaks. Models with A/C BUICK-1975 AND 1976 1. Disconnect the negative battery cable, drain the radiator and disconnect the hoses from the core. 2. Disconnect the wires from the defroster door, diverter door and temperature door. 3. Remove the four nuts securing the core assembly to the dash. 4. Remove the screw securing the defroster outlet tab to the heater assembly. 5. Remove the core assembly. To install: 6. Using sealer as necessary to prevent leaks at all joints and flanges. 7. Position the assembly onto the dash and tighten the retaining screws. 8. Reconnect the heater hoses, electrical connectors and negative battery cable. Refill the engine with coolant, start the vehicle and check for coolant leaks. OLDSMOBILE-1975 AND 1976 1. Disconnect the negative battery cable and drain the radiator. 2. Remove the heater case securing nuts. Disconnect the heater hoses. 3. Remove the instrument panel trim pad. 4. Remove the heater case-to-firewall bolts from inside the vehicle. 5. Remove the bottom air duct. 6. Remove the instrument panel crash pad. Unfasten the leads from the clock and glovebox light. 7. Remove the upper right hand trim panel. 8. Separate the air distribution manifold and defroster duct from the heater case. 9. Remove the lower dash trim panel. 10. Lift out the heater case and disconnect the hoses and cables from it. 11. Remove the core from the case. To install: 12. Install the core into the case. 13. Connect the hoses and cables to the case. 14. Install the lower dash trim panel. 15. Connect the air distribution manifold and defroster duct to the heater case. 16. Install the upper right hand trim panel. 17. Install the instrument panel crash pad. Connect the leads from the clock and glovebox light. 18. Install the bottom air duct. 19. Install the heater case-to-firewall bolts from inside the vehicle. 20. Install the instrument panel trim pad. 21. Install the heater case securing nuts. Connect the heater hoses. 22. Refill the radiator, connect the negative battery cable and check for leaks. PONTIAC-1975 AND 1976 1. Disconnect the negative battery cable and drain the coolant. 2. Disconnect the hoses from the heater core. Plug the tubes to prevent damage to the carpeting on removal. 3. Remove the three nuts and one screw holding the core and case assembly in place. 4. Remove the glove box and upper and lower instrument panel trim plates. 5. Remove the radio. 6. Remove the cold air duct. 7. Remove the heater outlet duct. 8. Remove the screw holding the defroster duct to the heater case. 9. Disconnect the vacuum hoses from the diaphragm, and the air conditioner temperature cable at the heater case. 10. Remove the core from the case, after removing the 3 retaining screws. To install: 11. Install the core into the case and tighten the 3 retaining screws. 12. Connect the vacuum hoses to the diaphragm, and the air conditioner temperature cable to the heater case. 13. Install the screw holding the defroster duct to the heater case. 14. Install the heater outlet duct. 15. Install the cold air duct. 16. Install the radio. 17. Install the glove box and upper and lower instrument panel trim plates. 18. Install the three nuts and one screw holding the core and case assembly in place. 19. Connect the hoses to the heater core. 20. Connect the negative battery cable and refill the coolant. 21. Start the engine and check for leaks. ALL MODELS-1977 AND LATER 1. Disconnect the negative battery cable and drain the cooling system. 2. Disconnect the heater hoses. 3. Remove the retaining bracket and the ground strap. Disconnect the module rubber seal and module screen. 4. Remove the right windshield wiper arm. 5. Remove the diaphragm connections, the hi/blower relay, the thermal switch mounting screws, and all the electrical connections from the module top. 6. Remove the module top cover and remove the core. To install: 7. Apply a strip of caulk-type sealer when installing the module top. 8. Install the core and module top cover. 9. Install the diaphragm connections, the hi/blower relay, the thermal switch mounting screws, and all the electrical connections to the module top. 10. Install the right windshield wiper arm. 11. Install the retaining bracket and the ground strap. Connect the module rubber seal and module screen. 12. Connect the heater hoses. 13. Connect the negative battery cable and refill the cooling system. 14. Start the engine and check for coolant and vacuum leaks. Fig. Fig. 1: To remove the heater core, first remove the rubber seal Fig. Fig. 2: Remove the windshield washer nozzle attaching screw Fig. Fig. 3: Remove the washer nozzle from the heater module Fig. Fig. 4: Remove the module top attaching screws Fig. Fig. 5: Be sure to remove the module screws in the well Fig. Fig. 6: Remove the module cover Fig. Fig. 7: Remove the heater core hoses; be sure the cooling system is drained first Fig. Fig. 8: Remove the heater core retainer Fig. Fig. 9 Remove the heater core Back to Top Drive Train GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Diesel Engine Adjustments Before making any adjustments, check the injection timing, and adjust if necessary. Also note that these adjustments should be performed together. The vacuum valve adjustment (THM350's only) on 1979 and later models requires the use of several special tools. If you do not have these tools at your disposal, refer the adjustment to a qualified, professional technician. Print THROTTLE ROD See Figure 1 1. If equipped with cruise control, remove the clip from the control rod, then remove the rod from the bellcrank. 2. Remove the throttle valve cable (THM200) or detent cable (THM350) from the bellcrank. 3. Loosen the locknut on the throttle rod, then shorten the rod several turns. 4. Rotate the bellcrank to the full throttle stop, then lengthen the throttle rod until the injection pump lever contacts the injection pump full throttle stop. Release the bellcrank. 5. Tighten the throttle rod locknut. 6. Connect the throttle valve or detent cable and cruise control rod to the bellcrank. Adjust if necessary. Fig. Fig. 1: Diesel throttle linkage THROTTLE VALVE (TV) OR DETENT CABLE See Figure 2 1979-82 Models 1. Make sure the ignition switch is off. Depress and hold the metal readjustment tab all the way down. This is located on the engine end of the Throttle Valve cable. Move the slider until it is located directly against the fitting, and then release the adjustment tab. 2. Rotate the throttle lever to give wide open throttle position. Watch the slider as you do this; it must move toward the lever as you rotate the throttle. If the slider works properly, this will complete the adjustment. After the adjustment, make sure the cable works freely after the engine has warmed to operating temperature. 1983-84 Models 1. Disconnect the transmission detent cable from the throttle assembly. If the vehicle has cruise control, disconnect it from the cruise control servo rod as well. 2. Depress and hold the metal lock tab on the upper end of the cable. Move the slider through the fitting away from the bellcrank lever assembly until the slider stops against the metal fitting. Release the metal tab. 3. Install the cruise control serve rod if the vehicle has cruise control. Reconnect the cable. Then, rotate the bellcrank lever assembly until it reaches the full throttle stop and release it. Fig. Fig. 2: Diesel throttle valve adjustment VACUUM VALVE 1978 Models See Figure 3 1. Remove the throttle rod from the bellcrank. 2. Loosen the transmission vacuum valve attaching bolts just enough to disengage the valve from the injection pump shaft. 3. Hold the injection pump lever against the full throttle stop. 4. Rotate the valve to the full throttle position, then insert a 0.090 in. (2.28mm) pin to hold the valve in the full throttle position. 5. Rotate the assembly clockwise until the injection pump lever is contacted. 6. While holding the assembly in contact with the lever, tighten the two bolts holding the vacuum valve to the pump, remove the pin and release the lever, and reconnect the throttle rod to the bellcrank. Fig. Fig. 3: Vacuum valve adjustment; 1978 diesel models 1979 and Later See Figures 4, 5, 6 and 7 1. Remove the air cleaner assembly. 2. Remove the air intake crossover from the intake manifold. Cover the intake manifold passages to prevent foreign material from entering the engine. 3. Disconnect the throttle rod from the injection pump throttle lever. 4. Loosen the transmission vacuum valve-to-injection pump bolts. 5. Mark and disconnect the vacuum lines from the vacuum valve. 6. Attach a carburetor angle gauge adapter (Kent-Moore tool J-26701-15 or its equivalent) to the injection pump throttle lever. Attach an angle gauge (J-26701 or its equivalent) to the gauge adapter. 7. Turn the throttle lever to the wide open throttle position. Set the angle gauge to 0. 8. Center the bubble in the gauge level. 9. Set the angle gauge to the correct setting according to the year and type of engine. 10. Attach a vacuum gauge to port 2 and a vacuum source (e.g. hand-held vacuum pump) to port 1 of the vacuum valve (as illustrated). 11. Apply 18-22 in. Hg of vacuum to the valve. Slowly rotate the valve until the vacuum reading drops to the correct value. 12. Tighten the vacuum valve retaining bolts. 13. Reconnect the original vacuum lines to the vacuum valve. 14. Remove the angle gauge and adapter. 15. Connect the throttle rod to the throttle lever. 16. Install the air intake crossover, using new gaskets. 17. Install the air cleaner assembly. Fig. Fig. 4: Angle gauge position for vacuum valve adjustment is dependent on the type of throttle lever used Fig. Fig. 5: Angle gauge settings Fig. Fig. 6: Vacuum setting values Fig. Fig. 7: Vacuum valve adjustment; 1979 and later Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Extension Housing Seal REMOVAL & INSTALLATION Print 1. Disconnect the negative battery cable. 2. Raise and properly support the vehicle 3. Mark the driveshaft and remove it from the vehicle. 4. Carefully distort the seal with a punch and remove it from the extension housing. Be careful not to damage the housing. To install: 5. Apply a non-hardening sealer on the outside of the new seal and drive the new seal into the housing using the proper tool. 6. Install the driveshaft with the marks aligned. 7. Lower the car and reconnect the negative battery cable. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Fluid Pan REMOVAL & INSTALLATION Print The fluid should be changed with the transmission warm. A 20 minute drive at highway speeds should accomplish this. 1. Raise and support the vehicle, preferably in a level attitude. 2. On some models it may be necessary to remove the crossmember, make sure to support the transmission if this is necessary. 3. Place a large pan under the transmission pan. Remove all the front and side pan bolts. Loosen the rear bolts about four turns. 4. Pry the pan loose and let it drain. 5. Remove the pan and gasket. Clean the pan thoroughly with solvent and air dry it. Be very careful not to get any lint from rags in the pan. It is normal to find a SMALL amount of metal shavings in the pan. An excessive amount of metal shavings indicates transmission damage which must be handled by a professional automatic transmission mechanic. 6. Install the pan with a new gasket. Tighten the bolts evenly to 12 ft. lbs. 7. Lower the vehicle and add the proper amount of DEXRON®II automatic transmission fluid through the dipstick tube. 8. Start the engine in PARK and let it idle. Do not race the engine. Shift into each shift lever position, shift back into PARK , and check the fluid level on the dipstick. The level should be 1 / 4 in. (6mm) below ADD. Be very careful not to overfill. Recheck the level after the vehicle has been driven long enough to thoroughly warm up the transmission. Add fluid as necessary. The level should then be at FULL. FILTER SERVICE See Figures 1, 2, 3, 4 and 5 1. Remove the fluid pan. 2. Remove the strainer-to-valve body screws, the strainer, and the gasket. Most transmissions will have a throw-away filter instead of a strainer. On the 400 transmission, remove the filter retaining bolt, filter, and intake pipe O-ring. 3. If there is a strainer, clean it in solvent and air dry. 4. Install the new filter or cleaned strainer with a new gasket. Tighten the screws to 12 ft. lbs. (16 Nm). On the 400, install a new intake pipe O-ring and a new filter, tightening the retaining bolt to 120 inch. lbs. (14 Nm). 5. Install the pan with a new gasket and add the proper amount of DEXRON®II automatic transmission fluid through the dipstick tube. Follow the procedure in removal and installation. Fig. Fig. 1: To replace the filter, start by removing the bolts on all but one side. These bolts will hold the pan while the fluid is draining Fig. Fig. 2: Loosen, but don't remove, the remaining bolts a few turns to allow the fluid in the pan to drain Fig. Fig. 3: After the fluid has drained, remove the remaining bolts and remove the pan Fig. Fig. 4: On this model, the filter is retained by a clip Fig. Fig. 5: Remove the filter from the valve body assembly Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Gasoline Engine Adjustments INTERMEDIATE BAND Print Turbo Hydra-Matic 250 Only the 250 series has an externally adjustable band; the procedure is covered below. The intermediate band must be adjusted with every required fluid change or whenever there is slippage. 1. Position the shift lever in NEUTRAL. 2. Loosen the locknut on the right side of the transmission. Tighten the adjusting screw to 30 inch lbs. (3 Nm). SHIFT LINKAGE See Figure 1 1. Loosen the clamp spring screw on the shift linkage clamp. This is the screw which will slide up and down the rod coming down from the steering column once it is loosened. 2. Set the lever on the transmission into NEUTRAL by moving it counterclockwise to the L1 detent, then clockwise the correct number of detent positions to NEUTRAL. With three speed automatics, move the lever three positions to NEUTRAL ; with four speed overdrive units, move it four positions to NEUTRAL. 3. Place the transmission selector lever (in the vehicle) in NEUTRAL as determined by the stop in the steering column. DO NOT Use the indicator pointer for reference. 4. Hold the clamp (into which the clamp spring screw is threaded) flush against the equalizer shaft lever and then tighten the shift linkage screw just finger tight. You must not exert any force in either direction on the rod or equalizer lever as you tighten the screw. Once the screw is hand tight and its position is fixed, torque it to 21 ft. lbs. (29 Nm). 5. Check that the key cannot be removed and that the steering wheel is not locked with the key in Run and the transmission in REVERSE . Check that the key can be removed and the transmission linkage is locked when the key is in Lock and the transmission is in PARK . Be sure the vehicle will start only in PARK and NEUTRAL . If it starts in any gear, the neutral start switch must be adjusted. Start the engine and check for proper shifting in all ranges. Fig. Fig. 1: Exploded view of a shift linkage assembly; all models similar THROTTLE VALVE (TV) CABLE See Figures 2 and 3 200-4R and 700-4R Models 1. Make sure the ignition switch is off. Depress and hold the metal readjustment tab all the way down. This is located on the engine end of the Throttle Valve cable. Move the slider until it is located directly against the fitting, and then release the adjustment tab. 2. Rotate the throttle lever to give wide open throttle position. Watch the slider as you do this; it must move toward the lever as you rotate the throttle. If the slider works properly, this will complete the adjustment. After the adjustment, make sure the cable works freely after the engine has warmed to operating temperature. Fig. Fig. 2: Throttle valve cable adjustment; 200-4R and 700-4R models All Other Models 1. With a small screwdriver, pry gently on the bottom of the snap lock to release the detent cable. 2. Push the throttle lever to the wide open throttle position (engine off) and hold. Push the snaplock tab downward until flush with the cable. Fig. Fig. 3: Throttle valve cable adjustment; snap lock type DETENT (DOWNSHIFT) SWITCH ADJUSTMENT See Figure 4 Turbo Hydra-Matic 400 All the General Motors divisions covered in this guide use the same detent switch on their THM 400 equipped models. The switch is mounted on the accelerator pedal bracket and is for all intents and purposes, self-adjusting. If a new switch is installed, a preliminary adjustment should be performed according to the accompanying illustration. 1. Perform the adjustment with the engine off. 2. Push the plunger of the downshift switch forward until it is flush with the switch housing. 3. Push the accelerator pedal to the wide open throttle position to set the switch. Fig. Fig. 4: Detent switch adjustment Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Identification See Figures 1, 2, 3, 4 and 5 Print General Motors Turbo Hydra-Matic transmissions are used in all models covered in this guide. Through the years 1975-83, four basic transmission series have been used, covering four load capacities. The 200 series, which includes the 200C and 200-4R. The 250 series, which includes the 250C. The 350/375B series, including the 350C. And the 400. Starting in 1984, most of the automatics used were in the 200 Series. The 200C offers a lockup clutch; the 2004R offers not only the lockup function, but a 4-speed, overdrive capability. These two transmissions are used through 1990. In addition, there is a 700 Series unit, known as the 700R4. This unit has four speeds with converter lockup. Fig. Fig. 1: TH-250, 350, 375B pan shape Fig. Fig. 2: TH-200 pan shape Fig. Fig. 3: TH-400 pan shape Fig. Fig. 4: TH-200-4R pan shape Fig. Fig. 5: TH-700-4R pan shape Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Neutral Safety/Backup Switch See Figure 1 Print 1977 and later full size Buick, Olds and Pontiac vehicles do not have a neutral safety switch. Instead, these vehicles have a mechanical interlock between the lock and the transmission selector, which is nonadjustable. REMOVAL & INSTALLATION 1. Remove any trim panels which may interfere with the switch removal. 2. Remove the switch attaching screws and disconnect the electrical connector. 3. Remove the switch. To install: 4. Place the shift lever in NEUTRAL . 5. Mount the switch but do not tighten the screws. Reconnect the electrical connector. 6. Move the switch until you can insert a gauge pin, 0.092 in. (2.33mm), for 1975-76, into the hole in the switch and through to the alignment hole. 7. Tighten the screws and remove the pin. 8. Step on the brake pedal and check to see that the engine will only start in NEUTRAL or PARK . Fig. Fig. 1: Neutral safety/backup switch adjustment Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Transmission REMOVAL & INSTALLATION Print See Figures 1 and 2 1. Disconnect the negative (-) battery cable. Open the hood and place protectors on the fenders. Remove the air cleaner assembly. 2. Disconnect the detent cable at its upper end. 3. Remove the transmission oil dipstick, and the bolt holding the dipstick tube if it is accessible. 4. Raise the vehicle and safety support it with jackstands. If a floor pan reinforcement is used, remove it if it interferes with driveshaft removal or installation. 5. Disconnect the speedometer cable at the transmission. 6. Disconnect the shift linkage at the transmission. 7. Disconnect all electrical leads at the transmission and any clips that hold these leads to the transmission case. 8. Remove the flywheel cover and matchmark the flywheel and torque converter for later assembly. 9. Remove the torque converter-to-flywheel bolts and/or nuts. 10. On gasoline engined vehicles, disconnect the catalytic converter support bracket. 11. Remove the transmission support-to-transmission mount bolt and transmission support-to-frame bolts, and any insulators (if used). 12. Position a transmission jack under the transmission and raise it slightly. 13. Slide the transmission support rearward. 14. Loosen the transmission enough to gain access to the oil cooler lines and detent cable attachments. 15. Disconnect the oil cooler lines and detent cable. Plug all openings. 16. Support the engine and remove the engine-to-transmission bolts. 17. Disconnect the transmission assembly, being careful not to damage any cables, lines or linkage. 18. Install a C-clamp or torque converter holding tool onto the transmission housing to hold the converter in the housing. Remove the transmission assembly from the vehicle (a hydraulic floor jack is best for this). To install: Fig. Fig. 1: Transmission oil cooler lines Fig. Fig. 2: Transmission mounting; all models similar 19. Install the transmission assembly into the vehicle (a hydraulic floor jack is best for this). When installing the flex plate-to-converter bolts, make sure that the weld nuts on the converter are flush with the flex plate and that the converter rotates freely by hand. Coat the threads with thread locking compound, hand-start the three bolts, tighten them finger tight and torque them evenly to 35 ft. lbs. (48 Nm). 20. Support the engine and install the engine-to-transmission bolts. Torque the bolts to 40 ft. lbs. (54 Nm). 21. Connect the oil cooler lines and detent cable. 22. Slide the transmission support forward. 23. Position a transmission jack under the transmission and raise it slightly. 24. Install the transmission support-to-transmission mount bolt and transmission support-to-frame bolts, and any insulators (if used). 25. On gasoline engined vehicles, connect the catalytic converter support bracket. 26. Install the flywheel cover. 27. Connect all electrical leads to the transmission and any clips that hold these leads to the transmission case. 28. Connect the shift linkage at the transmission. 29. Connect the speedometer cable at the transmission. 30. Check to see if all under vehicle components and fasteners are properly installed and torqued. 31. Lower the vehicle safely. 32. Install the transmission oil dipstick, and the bolt holding the dipstick tube if it is accessible. 33. Connect the detent cable at its upper end. 34. Connect the negative (-) battery cable. Recheck all procedures for completion of repair. Close the hood and remove the protectors on the fenders. 35. Install the air cleaner assembly. Refill the transmission with fluid as outlined in the "Oil Pan" section in this information. 36. Start the vehicle and check operation. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Vacuum Modulator REMOVAL & INSTALLATION Print 1. Raise and safely support the vehicle 2. Locate and remove the modulator retaining bolt. Disconnect the vacuum line. 3. Pull the modulator straight back from the case. 4. Installation is the reverse of removal. Lube the O-ring with petroleum jelly and torque the retaining bolt to 20 ft. lbs. Back to Top Suspension & Steering GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Coil Springs REMOVAL & INSTALLATION Print See Figures 1, 2 and 3 CAUTION The coil springs are under a considerable amount of tension. Be extremely careful when removing or installing them; they can exert enough force to cause serious injury. Use only approved spring compressors for suspension servicing. 1. Raise the front of the vehicle and support with jackstands at the frame so the control arms hang free. 2. Remove the shock absorber. Disconnect the stabilizer bar at the steering knuckle. 3. Support the inner end of the control arm with a floor jack. 4. Raise the jack enough to take the tension off the lower control arm pivot bolts. Install the spring compressor through the spring and frame. Tighten the compressor until the lower control arm pivots bolts can be removed. Compress the spring far enough to remove the lower control arm and spring. 5. Remove the lower ball joint nut and separate from the knuckle using a ball joint separator tool J-23742 or equivalent. 6. Chain the spring to the lower control arm. 7. Remove first the rear, then the front pivot bolt. 8. Cautiously loosen the spring compressor until all spring tension is released. 9. Note the way in which the spring is installed in relation to the drain holes on the control arm and remove it. To install: 10. On installation, position the spring to the control arm and raise it into place. On 1985 and later Oldsmobile models, note that the spring must be positioned so that the end of the coil covers all or part of one inspection/drain hole in the lower control arm, and the other hole must be only partly covered. 11. Compress the spring far enough to install the front and rear pivot bolts. 12. Install the pivot bolts and torque the nuts to 100 ft. lbs. (136 Nm) on models built through 1984. On 1985-90 models, torque the bolts to 90 ft. lbs. (122 Nm). 13. Install the lower ball joint to the knuckle, torque the nut to 85 ft. lbs. (112 Nm) and install a new cotter pin. 14. Replace the shock absorber and stabilizer bar. Fig. Fig. 1: Compressing the front coil spring Fig. Fig. 2: Spring compressed and ready to install Fig. Fig. 3: Proper coil spring installation Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide FRONT SUSPENSION See Figure 1 Print The front suspension is designed to allow each wheel to compensate for changes in the road surface level without appreciably affecting the opposite wheel. Each wheel is independently connected to the frame by a steering knuckle, ball joint assemblies, and upper and lower control arms. The control arms are specifically designed and positioned to allow the steering knuckles to move in a prescribed three dimensional arc. The front wheels are held in proper relationship to each other by two tie rods which are connected to steering arms on the knuckles and to an intermediate rod. Chassis coil springs are mounted between the spring housings on the frame or front end sheet metal and the lower control arms. Ride control is provided by double, direct acting, shock absorbers mounted inside the coil springs and attached to the lower control arms by bolts and nuts. The upper portion of each shock absorber extends through the upper control arm frame bracket and is secured with two grommets, two grommet retainers, and a nut. Side roll of the front suspension is controlled by a spring steel stabilizer shaft. It is mounted in rubber bushings which are held to the frame side rails by brackets. The ends of the stabilizer are connected to the lower control arms by link bolts isolated by rubber grommets. The upper control arm is attached to a cross shaft through isolating rubber bushings. The cross shaft, in turn, is bolted to frame brackets. A ball joint assembly is riveted to the outer end of the upper arm. It is pre-loaded by a rubber spring to insure proper seating of the ball in the socket. The upper ball joint is attached to the steering knuckle by a torque prevailing nut. The inner ends of the lower control arm have pressed in bushings. Bolts, passing through the bushings, attach the arm to the frame. The lower ball joint assembly is a press fit in the arm and attaches to the steering knuckle with a torque prevailing nut. Rubber grease seals are provided at ball socket assemblies to keep dirt and moisture from entering the joint and damaging bearing surfaces. Fig. Fig. 1: An exploded view of front suspension components Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Front End Alignment See Figures 1 and 2 Print The procedure for checking and adjusting front wheel alignment requires specialized equipment and professional skills. The following descriptions and adjustment procedures are for general reference only. Front wheel alignment is the position of the front wheels relative to each other and to the vehicle. It is determined, and must be maintained to provide safe, accurate steering with minimum tire wear. Many factors are involved in wheel alignment and adjustments are provided to return those that might change due to normal wear to their original value. The factors which determine wheel alignment are dependent on one another; therefore, when one of the factors is adjusted, the others must be adjusted to compensate. Descriptions of these factors and their affects on the vehicle are provided below. Do not attempt to check and adjust the front wheel alignment without first making a thorough inspection of the front suspension components. CASTER Caster angle is the number of degrees that a line drawn through the steering knuckle pivots is inclined from the vertical, toward the front or rear of the vehicle. Caster improves directional stability and decreases susceptibility to crosswinds or road surface deviations. CAMBER Camber angle is the number of degrees that the centerline of the wheel is inclined from the vertical. Camber reduces loading of the outer wheel bearing and improves the tire contact patch while cornering. TOE-IN Toe-in is the difference of the distance between the centers of the front and rear of the front wheels. It is most commonly measured in inches, but is occasionally referred to as an angle between the wheels. Toe-in is necessary to compensate for the tendency of the wheels to deflect rearward while in motion. Due to this tendency, the wheels of a vehicle, with properly adjusted toe-in, are traveling straight forward when the vehicle itself is traveling straight forward, resulting in directional stability and minimum tire wear. The Do-it-Yourself mechanic should not attempt to perform any wheel alignment procedures. Expensive alignment tools are needed and would not be cost efficient to purchase these tools. The wheel alignment should be performed by a certified alignment technician using the proper alignment tools. Fig. Fig. 1: Caster, camber and toe-in STEERING AXIS INCLINATION Steering axis inclination is the number of degrees that a line drawn through the steering knuckle pivots is inclined from the vertical, when viewed from the front of the vehicle. This, in combination with caster, is responsible for directional stability and self-centering of the steering. As the steering knuckle swings from lock to lock, the spindle generates an arc, the high point being the straight-ahead position of the wheel. Due to this arc, as the wheel turns, the front of the vehicle is raised. The weight of the vehicle acts against this lift and attempts to return the spindle to the high point of the arc, resulting in self-centering, when the steering wheel is released, and straight line stability. Fig. Fig. 2: Steering axis inclination Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Front Wheel Bearings REPLACEMENT Print See Figures 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 1. Remove the front wheel and caliper assembly. Do not allow the caliper to hang by it's hose, secure it with a length of wire. 2. Remove the hub bearing cup and the cotter pin. 3. Remove the castellated nut and washer, then remove the outer bearing race and hub assembly. 4. Pry the seal from the hub, then remove the inner roller bearing assembly. 5. To replace the inner or outer bearing race, insert a brass drift into the hub, indexing the end of the drift with the notches in the hub and tap with a hammer. To install: 6. Clean off any grease from the hub and spindle. 7. Drive the new inner and outer bearing races into the hub. Use tools J-8092 and J-8850 for the inner race and tools J-8092 and J-8457 for the outer race or their equivalent. 8. Use an approved high temperature front wheel bearing grease. Do not mix greases as this can change the properties and lead to poor performance. 9. Apply a thin film of grease to the spindle at the outer bearing seat and at the inner bearing seat, shoulder, and seal seat. 10. Put a small quantity of grease inboard of each bearing cup in the hub. This can be applied with your finger, forming a dam to provide extra grease availability to the bearing and to keep thinned grease from flowing out of the bearing. 11. Fill the bearing cone and roller assemblies full of grease. Work the grease thoroughly into the bearings between the rollers, cone and the cage. Failure to do so could result in premature bearing failure. 12. Place the inner bearing cone and roller assembly in the hub. Then, using your finger, put an additonal amount of grease outboard of the bearing. 13. Install a new seal using a large socket or flat plate until the seal is flush with the hub. Apply force only on the outer edge of the seal, not on the rubber portion. Lubricate the seal lip with a thin layer of grease. 14. Carefully install the rotor and hub assembly. Place the outer cone and roller assembly in the outer bearing cup. Install the washer and nut and intially tighten the nut to 12 ft. lbs (16 Nm) while turning the wheel assembly forward by hand. Put an additional quantity of grease outboard of the bearing. This provides extra grease availability to the bearing. 15. Adjust the wheel bearings according to the procedures in Routine Maintenance . Fig. Fig. 1: An exploded view of the hub assembly Fig. Fig. 2: Carefully pry the bearing cup out, be careful not to distort it Fig. Fig. 3: Remove the cotter pin from the spindle; always use a new cotter pin during reassembly Fig. Fig. 4: Remove the castellated nut and the washer Fig. Fig. 5: Once the above mentioned nut and washer is removed, the outer bearing can be removed from the hub Fig. Fig. 6: Carefully pull the hub assembly off of the spindle Fig. Fig. 7: Pry the seal from the hub; once the seal is removed the inner bearing can be removed Fig. Fig. 8: When installing the new seal, be sure to apply force only on the outer edge of the seal. Don't forget the inner bearing must be installed first Fig. Fig. 9: Installing the inner bearing race Fig. Fig. 10: Installing the outer bearing race Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Knuckle and Spindle REMOVAL & INSTALLATION Print In order to perform this procedure, you will need a tool for forcing ball joint studs out of the control arms. It would also be helpful to have a tool that will permit you to press the tie rod end out of the steering knuckle. A special tool for seating the tie rod ends when installing them back into the knuckles, GM J-29193 or equivalent, will ensure proper seating. 1. Raise the vehicle and support it securely under the frame. Do not support the lower control arm yet. CAUTION Some brake pads contain asbestos, which has been determined to be a cancer causing agent. Never clean the brake surfaces with compressed air! Avoid inhaling any dust from any brake surface! When cleaning brake surfaces, use a commercially available brake cleaning fluid. 2. Refer to Brakes and remove the brake caliper. Then, refer to the procedure for removing the brake disc in the sameand remove the disc and hub. 3. Remove the three bolts attaching the water shield to the steering knuckle. Remove the shield and its gasket. Disconnect the tie rod ends from the steering knuckle as described later in the "Steering" section in this information. 4. Pry the knuckle seal off the knuckle carefully in order to avoid damaging the knuckle sealing surfaces and discard the old seal. 5. Remove the cotter pin and then loosen the ball joint stud retaining nut just a turn or two on both upper and lower ball joints. You want just enough clearance to break the ball joint studs loose in the control arms. CAUTION The nuts must remain on the studs with plenty of extra threads in order to prevent the release of spring tension. Use an appropriate special tool to press the upper and lower ball joint studs out of the control arms until the nuts bottom out against the arms. CAUTION There is tremendous spring pressure forcing the lower control arm downward. You must assure yourself that you have a floor jack or other appropriate means to safely and securely support the lower control arm by the area under the spring in the next step; otherwise, remove the spring as described earlier to eliminate spring tension. 6. Securely support the lower control arm by the area directly under the spring. You can locate a floor jack directly under the control arm and raise it just until is contacts the control arm to do this. Then, remove the nuts from the ball studs. 7. Remove the tie rod end cotter pin, nut and rod end using a tie rod puller tool J-6627-A. Refer to the "Steering" section in thisfor assistance. 8. Raise the upper control arm for clearance and rock the knuckle outward so the ball stud clears the knuckle. Then, pull the knuckle upward and off the lower ball joint stud and remove it. 9. Inspect the tapered holes in the steering knuckle, cleaning out dirt and checking for any out-of-roundness, cracking, deformation, or other damage. Replace the knuckle if there are any such indications or dangerous front end problems could result. To install: 10. Position the knuckle onto the lower ball joint stud and then raise the upper control arm, working the upper ball stud into the tapered hole in the top of the knuckle. 11. Install the ball joint stud nuts, torque them, and install the cotter pins as described under "Ball Joint" removal and installation earlier in this information. CAUTION It is vitally important that the tie rod end seat fully in the steering knuckle. You may want to use a tool such as GM J-29193 or equivalent to ensure complete seating. This tool is installed over the partly assembled knuckle and tie rod end and its nut is torqued to 15 ft. lbs. (20 Nm) to draw the tie rod end into the knuckle. 12. Install the tie rod end into the steering knuckle. Install the nut and torque it to 40 ft. lbs. (54 Nm). 13. Install a new shield-to-knuckle splash shield and install the shield, torquing the three mounting bolts to 120 inch lbs. (14 Nm). Grease its lips with wheel bearing grease and carefully install a new grease seal. 14. Repack the wheel bearings, install the hub and rotor, and readjust the bearings. 15. Install the caliper and remaining parts in reverse order, referring to the "Caliper" removal and installation procedure in Brakes . Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Lower Ball Joints See Figures 1 and 2 Print INSPECTION Before performing this inspection, make sure the wheel bearings are adjusted correctly and that the control arm bushings are in good condition. All models covered in this guide are equipped with wear indicators on the lower ball joint. As long as the indicator extends below the ball stud seat, replacement is unnecessary; if only the lower ball joint is bad, however, both upper and lower ball joints should be replaced. Fig. Fig. 1: Lower ball joint wear indicator REMOVAL & INSTALLATION 1. Raise the vehicle and support it securely. Support the lower control arm with a jack or jackstand. Remove the wheel. 2. Remove the lower ball stud cotter pin, and loosen the ball stud nut 2-3 turns. 3. Install a special tool designed for such work between the two ball studs, and press the stud downward in the steering knuckle to free it. Then, remove the stud nut. 4. Guide the lower control arm out of the opening in the splash shield with a putty knife or something similar. Lift up on the upper control arm and place a block of wood between it and the frame. Be careful not to put tension on the brake hose as you do this. 5. Remove the ball joint seal by prying off the retainer with a prybar or driving it off with a chisel. 6. Remove grease fittings and install a tool designed for this purpose and press the ball joint out of the lower control arm. On some models, you may have to disconnect the tie rod at the knuckle to do this. To install: 7. Position the ball joint in the control arm so that the grease purge on the seal faces inboard. Press the joint in with a tool designed for this purpose until it bottoms on the control arm. Remove the block of wood and then insert the ballstud through the steering knuckle hole on the control arm. 8. Turn the ball stud cotter pin hole so it faces fore and aft. Install the nut on the ball stud and torque it to: 105 ft. lbs. (140 Nm) on 1975-77 vehicles; 83 ft. lbs. (112 Nm) on 1978-79 vehicles; 90 ft. lbs. (122 Nm) on 1980-81 vehicles; 70 ft. lbs. (95 Nm) on 1982-83 models; and 90 ft. lbs. (122 Nm) on 1984-90 models. Then, as necessary, turn the nut tighter to line up one of the castellations with the cotter pin hole. Finally, install the cotter pin and bend both prongs down and back against the nut. Lubricate the joint until grease appears at the seal. Remove supports and lower the vehicle. Fig. Fig. 2: Pressing out the lower ball joint Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Lower Control Arm See Figures 1, 2, 3, 4, 5 and 6 Print REMOVAL & INSTALLATION CAUTION The coil springs are under a considerable amount of tension. Be extremely careful when removing or installing them; they can exert enough force to cause serious injury. Use only approved spring compressors for suspension servicing. 1. Remove the spring as described earlier. 2. Remove the ball stud from the steering knuckle as described earlier. 3. Remove the control arm pivot bolts and the control arm. On later models, you may have to guide the control arm out of the splash shield, using a putty knife or similar tool to protect parts. To install: 4. Position the control arm into spring and locate the bushing-to-frame brackets. If any bolts are to be replaced, do so with bolts of equal strength and quality. 5. Install the bolts and nuts loosely. Connect the control arm with the knuckle and torque the nut to 83 ft. lbs. (112 Nm). Install a new cotter pin. 6. With a jack supporting the lower control arm, torque the attaching bolts. 7. Install the shock absorber, sway bar and wheel. Lower the vehicle and check operation. Fig. Fig. 1: Exploded view of the lower control arm CONTROL ARM BUSHING REPLACEMENT Front Bushing 1. Remove the lower control arm. 2. Using proper bushing removal tools remove the bushing from the control arm. To install: 3. Using suitable bushing driver tools, install the bushing onto the control arm. 4. Remove the bushing driver tools and install a suitable bushing flaring tool. 5. Turn the nut until the bushing is flared. Fig. Fig. 2: Removing the front bushing Fig. Fig. 3: Installing the front bushing Fig. Fig. 4: Flaring the front bushing Rear Bushing 1. Remove the bushing from the control arm using the proper bushing removal tools. To install: 2. Install the bushings using the appropriate tools. When properly installed, the bushings should bottom against the control arm. 3. Install the control arm using the procedures above. Fig. Fig. 5: Removing the rear bushing Fig. Fig. 6: Installing the rear bushing Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Shock Absorbers REMOVAL & INSTALLATION Print See Figures 1, 2, 3 and 4 1. Raise the vehicle, and with an open end wrench hold the upper stem of the shock absorber from turning. Remove the upper stem retaining nut, retainer and grommet. 2. Remove the two bolts retaining the lower shock absorber pivot to the lower control arm and then pull the shock out through the bottom of the control arm. 3. With the lower retainer and the rubber grommet in place over the upper stem, install the shock (fully extended) back through the lower control arm. 4. Install the upper grommet, retainer and nut onto the upper stem. 5. Hold the upper stem from turning with an open end wrench and then tighten the retaining nut. 6. Reinstall the retainers on the lower end of the shock. Fig. Fig. 1: Exploded view of the front shock absorber mounting Fig. Fig. 2: Remove the upper stem retaining nut, be sure to hold the stem of the shock absorber with an open end wrench to prevent turning Fig. Fig. 3: Remove the two lower retaining bolts Fig. Fig. 4: Pull the shock absorber through the lower control arm TESTING Visually inspect the shock absorber. If there is evidence of leakage and the shock absorber is covered with oil, the shock has reached the end of its life and should be replaced. If there is no sign of excessive leakage (a small amount of weeping is normal) bounce the vehicle at one corner by pressing down on the fender or bumper and releasing. When you have the vehicle bouncing as much as you can, release the fender or bumper. The vehicle should stop bouncing after the first rebound. If the bouncing continues past the center point of the bounce more than once, the shock absorbers are worn and should be replaced. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Sway Bar See Figures 1, 2 and 3 Print REMOVAL & INSTALLATION 1. Raise the front end of the vehicle and safely support it with jackstands. 2. Disconnect each side of the sway bar linkage by removing the nut from the link bolt. Pull the bolt from the linkage and remove the retainers, grommets and spacer. 3. Remove the bracket-to-frame or body bolts on both sides of the vehicle and remove the sway bar, rubber bushings and brackets. To install: 4. Make sure the rubber bushings are installed squarely in the bracket with the slit in the bushings facing the front of the vehicle. Torque the sway bar link nuts to 13 ft. lbs. (18 Nm). Fig. Fig. 1: Exploded view of the sway bar mounts Fig. Fig. 2: Removing the sway bar link bolt Fig. Fig. 3: Removing the bracket-to-frame bolts Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Upper Ball Joints See Figures 1, 2, 3 and 4 Print INSPECTION Before performing this inspection, make sure the wheel bearings are adjusted correctly and that the control arm bushings are in good condition. All models covered in this guide are equipped with wear indicators on the lower ball joint. As long as the indicator extends below the ball stud seat, replacement is unnecessary; if only the lower ball joint is bad, however, both upper and lower ball joints should be replaced. 1. Raise the vehicle by placing the jack under the lower control arm at the spring seat. 2. Raise the vehicle until there is a 1-2 in. (25-51mm) clearance under the wheel. 3. Insert a bar under the wheel and pry upward. If the wheel raises more than 1 / 8 in. (3mm), the ball joints are worn. Determine whether the upper or lower ball joint is worn by visual inspection while prying on the wheel. REMOVAL & INSTALLATION 1. Raise the vehicle and support securely. Support the lower control arm securely with jackstands. Remove the tire and wheel. 2. Remove the upper ball stud cotter pin and loosen the ball stud nut just one turn. 3. Procure a special tool designed to press out ball joints. These tools are available at most automotive parts stores. Locate the tool between the upper and lower ball joints and press the joints out of the steering knuckle. Remove the tool. 4. Remove the ball joint stud nut, and separate the joint from the steering knuckle. Lift the upper arm up and place a block of wood between the frame and the arm to support it. 5. With the control arm in the raised position, drill a hole 6. Use a 1 1 / 4 in. (6mm) deep hole into each rivet. Use a 1 / 8 in. (3mm) drill bit. / 2 in. drill bit and drill off the heads of each rivet. 7. Punch out the rivets using a small punch and then remove the ball joint. 8. Install the new ball joint using fasteners that meet GM specifications. Bolts should come in from the bottom with the nuts going on top. Torque to specifications included in the ball joint kit. 9. Turn the ball stud cotter pin hole to the fore and aft position on models up to 1981. 1982 and later models use no cotter pin. Remove the block of wood from between the upper control arm and frame. 10. Clean and inspect the steering knuckle hole. Replace the steering knuckle if any out of roundness is noted. 11. Insert the ball stud into the steering knuckle, and install and torque the stud nut to 60 ft. lbs. (81 Nm). Install a new cotter pin. If the nut must be turned to align cotter pin holes, turn them further. Do not back off! 12. Install a lube fitting, and fill the joint with fresh grease. 13. Remove the lower control arm support (jack, etc.) and lower the vehicle. Fig. Fig. 1: Ball joint cotter pin installation Fig. Fig. 2: Drilling the upper ball joint rivet heads Fig. Fig. 3: When installing the new upper ball joints, make sure the nuts are on top Fig. Fig. 4: Ball joint removal tool Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Upper Control Arm See Figures 1, 2, 3 and 4 Print REMOVAL & INSTALLATION 1. Raise the vehicle and support safely with jackstands. 2. Support the outer end of the lower control arm with a jack. CAUTION Leave the jack in place during removal and installation, in order to keep the spring and control arm positioned. 3. Remove the wheel. 4. Separate the upper ball joint from the steering knuckle as described above under Upper Ball Joint Replacement. 5. Remove the control arm shaft-to-frame nuts. Tape the shims together and identify them so that they can be installed in the positions from which they were removed. 6. Remove the bolts which attach the control arm shaft to the frame and remove the control arm. Note the positions of the bolts. To install: 7. Make sure that the shaft-to-frame bolts are installed in the same position they were in before removal and that the shims are in their original positions. 8. Use free running nuts (not locknuts) to pull serrated bolts through the frame. 9. Install the locknuts. Tighten the thinner shim pack first. 10. After the vehicle has been lowered to the ground, bounce the front end to center the bushings and then tighten the bushing collar bolts to 45 ft. lbs. (61 Nm). Tighten the shaft-to-frame bolts to 90 ft. lbs. (122 Nm). The control arm shaft nuts are tightened to 75 ft. lbs. (102 Nm) on models through 1982. Use 85 ft. lbs. (115 Nm) on 1983-90 models. Fig. Fig. 1: Exploded view of the upper control arm CONTROL ARM BUSHING REPLACEMENT 1. Remove the upper control arm assembly from the car. 2. Remove the nuts from the ends of the pivot shaft. 3. Push the bushings out of the control arm using suitable bushing removal tools. To install: 4. Place the pivot shaft in the control arm and push new bushings into the control arm and over the end of the pivot shaft using suitable bushing driver tools. Upper control arm bushings are to be installed 0.5 in. (13.3 mm) from the face of the control arm to the bushing outer sleeve. 5. Assemble the nuts to the ends of the pivot shafts. 6. Install the upper control arm assembly following the procedures above. Fig. Fig. 2: Upper control arm bushings Fig. Fig. 3: Removing the upper control arm bushing Fig. Fig. 4: Make sure the bushings are pressed in the proper distance Back to Top Brakes GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Adjustments DISC BRAKES Print There is no adjustment provision on hydraulic disc brakes; they are inherently self-adjusting. DRUM BRAKES Drum brakes are self-adjusting, but provision is made for manual adjustment as follows: 1. Raise the rear of the vehicle and support it with jackstands. 2. The inner sides of the brake backing plates have a lanced area, oblong in shape. Knock this area out with a punch. You will have to remove the brake drum to clean out any metal pieces that will be deposited by the punch, and you will have to purchase rubber plugs at a parts distributor to plug the punched holes now in the backing plats. Many vehicles will already have the holes punched and plugs installed. 3. Adjustment to tighten: A. Insert a brake adjusting spoon into the hole. B. Turn the star-shaped adjusting screw inside the drum with the spoon, until the wheel has a slight drag. Do this to both wheels until there is equal drag on each wheel. DO NOT make the adjustment overtight! 4. Adjustment to loosen and remove the drum: A. Insert a brake adjusting spoon and small prybar to hold the adjusting lever away from the sprocket. B. Back off each adjusting screw until the drum turns freely. If the brake shoes drag with the adjusters backed off all the way, the parking brake cables could be excessively tight. 1 BRAKE PEDAL / 4 in. on 1975 to 1984 models, 2 1 models and 3 / 3 in. on Hydro-boost systems. 3 / 4 in. on 1985 to 1990 The pedal travel is measured as the distance which the pedal moves towards the floor from the fully released position. Inspection should be made with the pedal firmly depressed and the brake system cold. Pedal travel should be 2 If equipped with power brakes, pump the 3 times with the engine OFF to remove vacuum reserve before checking pedal travel. 1. Under the dash, remove the pushrod-to-pedal clevis pin. 2. Loosen the pushrod adjusting locknut and adjust the pushrod. 3. After the correct travel is established, tighten the locknut. 4. Engage the pushrod and secure using the clevis pin. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide BRAKE SYSTEM Print CAUTION Some brake pads contain asbestos, which has been determined to be a cancer causing agent. Never clean the brake surfaces with compressed air! Avoid inhaling any dust from any brake surface! When cleaning brake surfaces, use a commercially available brake cleaning fluid. All Buick, Oldsmobile and Pontiac models covered in this guide are equipped with front disc brakes and rear drum brakes as standard equipment. Four wheel disc brakes are optional on some models. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Brake Bleeding The hydraulic brake system must be bled any time one of the lines is disconnected or any time air enters the system. If the brake pedal feels Print spongy upon application, and goes almost to the floor but regains height when pumped, air has entered the system. It must be bled out. Check for leaks that would have allowed the entry of air and repair them before bleeding the system. The correct bleeding sequence is: right rear wheel cylinder, left rear, right front, and left front. If the master cylinder is equipped with bleeder valves, bleed them first then go to the wheel cylinder nearest the master cylinder (left front) followed by the right front, left rear, and right rear. MANUAL BLEEDING See Figures 1 and 2 Standard Systems This method of bleeding requires two people, one to depress the brake pedal and the other to open the bleeder screws. 1. Clean the top of the master cylinder, remove the cover and fill the reservoirs with clean fluid. To prevent squirting fluid, replace the cover. CAUTION On vehicles with front disc brakes, it will be necessary to hold in the metering valve pin during the bleeding procedure. The metering valve is located beneath the master cylinder and the pin is situated under the rubber boot on the end of the combination valve housing. This may be taped in or held by an assistant. Never reuse brake fluid which has been bled from the system. 2. Fill the master cylinder with brake fluid. 3. Install a box-end wrench on the bleeder screw on the right rear wheel. 4. Attach a length of small diameter, clear vinyl tubing to the bleeder screw. Submerge the other end of the rubber tubing in a glass jar partially filled with clean brake fluid. Make sure the rubber tube fits on the bleeder screw snugly or you may be squirted with brake fluid when the bleeder screw is opened. 5. Have your friend slowly depress the brake pedal. As this is done, open the bleeder screw half a turn and allow the fluid to run through the tube. Close the bleeder screw, then return the brake pedal to its fully released position. 6. Repeat this procedure until no bubbles appear in the jar. Refill the master cylinder. 7. Repeat this procedure on the left rear, right front, and left front wheels, in that order. Periodically refill the master cylinder so it does not run dry. 8. If the brake warning light is on, depress the brake pedal firmly. If there is no air in the system, the light will go out. Fig. Fig. 1: Have an assistant pump the brake pedal while you bleed each wheel Fig. Fig. 2: Bleeder screw location on rear drum brakes Powermaster® System 1. Pump the brake pedal 10 times with the ignition switched off to remove all power boost effect from the system. Fill the reservoir to the indicated full mark with clean, fresh fluid meeting the specifications shown on the cover. 2. Disconnect the brake line connectors at the master cylinder outlet ports. Allow the fluid to bleed through the system by gravity until it flows out all four ports. Reconnect the brake lines to the ports. Refill the fluid reservoir, if necessary. 3. Tighten the connector closest to the cowl. Then, have an assistant slowly apply the brake pedal fully (50 lbs. pressure). As he holds this position, tighten the forward connector. Then, have the assistant release the pedal. Refill the fluid reservoir, if necessary. 4. Wait five seconds, and then have your assistant re-apply the brake pedal, and hold it down. Open the forward connector 1 / 2 turn to purge air. Before the pedal bottoms out, retighten the connector and have your assistant release the pedal again. Repeat the procedure in this step until all air is purged from this port. Refill the fluid reservoir, if necessary. 5. Repeat Steps 3 and 4 to bleed the remaining connectors (the connector closest to the cowl need not be bled). When the bleeding operation has been completed, operate the brakes with the ignition on and system pressure restored. Brake pedal travel should be normal and the brake warning indicator must not light when brakes are applied. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Brake Hoses and Pipes REMOVAL & INSTALLATION Print Brake Hose 1. Raise the end of the vehicle with the hose to be replaced. Secure the vehicle properly with jackstands. 2. If necessary, remove the wheel. 3. Note the hose routing for ease of installation later. 4. Remove any attaching brackets and loosen the fittings using a flare nut wrench only. 5. Remove the hose any plug any open lines. To install: 6. Install the brake hose and any brackets which were removed. 7. Torque all fittings to 10-15 ft. lbs (14-20 Nm). 8. Properly bleed the system. 9. Remove the jackstands and lower the vehicle. Brake Pipe 1. Raise the end of the vehicle with the line to be replaced. Secure the vehicle properly with jackstands. 2. If necessary, remove any components which will interfere with removal. 3. Note the line routing for ease of installation later. 4. Loosen the fittings using a flare nut wrench only. Plug the open line. 5. Trace the line from one end to the other and loosen the fitting using a flare nut wrench only. Plug any open lines. 6. Remove any retaining clips and remove the line from the vehicle. To install: 7. Obtain a replacement line. If it is longer than the original, one end must be cut and flared. 8. If necessary, bend tubing using an approved tubing bender only. When bending, don't kink or crack the line. If it does kink or crack, the line must be replaced. 9. Flush the line before installing. 10. Install the line and torque to 10-15 ft. lbs (14-20 Nm). 11. Bleed the system properly. Install any components removed earlier. BRAKE PIPE FLARING Flaring steel lines is a skill which needs to be practiced before it should be done on a line to be used on a vehicle. A special flaring kit with double flaring adapters is required. It is essential that the flare be done uniformly to prevent any leaks when the brake system is under pressure. Only steel lines, not copper lines, should be used. It is also mandatory that the flare be a double flare. With the supply of parts available today, a pre-flared steel brake line should be available to fit your needs. Due to the high pressures in the brake system and the serious injuries that could occur if the flare should fail, it is strongly advised that pre-flared lines should be installed when repairing the braking system. If a line were to leak brake fluid due to a defective flare, and the leak were to go undetected, brake failure would result. WARNING A double flaring tool must be used as single flaring tools cannot produce a flare strong enough to hold the necessary pressure. 1. Determine the length of pipe needed. Allow 1 / 8 in. (3.2 mm) for each flare. Cut using an appropriate tool. 2. Square the end of the tube with a file and chamfer the edges. Remove any burrs. 3. Install the required fittings on the pipe. 4. Install the flaring tool into a vice and install the handle into the operating cam. 5. Loosen the die clamp screw and rotate the locking plate to expose the die carrier. 6. Select the required die set and install in the carrier. 7. Insert the prepared line through the rear of the die and push forward until the line end is flush with the die face. 8. Make sure the rear of both halves of the die are resting against the hexagon die stops. Then rotate the locking plate to the fully closed position and clamp the die firmly by tightening the clamp screw. 9. Rotate the punch turret until the appropriate size points towards the open end of the line to be flared. 10. Pull the operating handle against the line resistance in order to create the flare, then return the handle to the original position. 11. Release the clamp screw and rotate the locking plate to the open position. 12. Remove the die set and the line then separate by gently tapping both halves on the bench. Inspect the flare for proper size and shape. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Brake Light Switch See Figure 1 Print REMOVAL & INSTALLATION 1. Disconnect the negative battery cable. 2. Disconnect the switch electrical connector. 3. Withdraw the switch from the pedal mounting bracket. To install: 4. Make sure the clip is in the pedal mounting bracket. 5. Depress the brake pedal and insert the switch. 6. Pull the brake pedal rearward until it contacts the brake pedal stop. You should not hear any more clicks. 7. Check stop lamp switch operation by applying and releasing the brake, make certain the stop lamps go off when the brake pedal is in the released position. Fig. Fig. 1: Brake light switch installation and adjustment Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Combination Valve See Figures 1 and 2 Print The combination valve used on the large Buicks, Oldsmobiles and Pontiacs is a three-function valve. It serves as a metering valve, balance valve, and brake warning switch. There are two different valves, one manufactured by Bendix and one manufactured by Kelsey-Hayes. Both valves serve the same function and differ only in minor details. In any case, all combination valves are non-adjustable and must be replaced if they are found to be defective. REMOVAL & INSTALLATION 1. Disconnect all the brake lines at the valve. Plug the lines to prevent contamination and loss of fluid. 2. Disconnect the warning switch wiring connector from the valve switch terminal. 3. Remove the attaching bolts and remove the valve. 4. Install the valve and torque the brake lines to 20 ft. lbs. (27 Nm) using flare nut wrench only. 5. Bleed the entire brake system after valve installation. Fig. Fig. 1: Combination valve mounting; all models similar Fig. Fig. 2: Cutaway view of the Bendix combination valve Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Hydraulic (Hydro-boost®) Power Booster REMOVAL and INSTALLATION Print See Figure 1 Power steering fluid and brake fluid cannot be mixed; also, power steering fluid damages seals designed for brake fluid, and brake fluid damages power steering type seals. 1. With the engine off, pump the brake pedal 5 times to deplete fluid stored in the accumulator. 2. Remove the two master cylinder mounting nuts and pull the master cylinder forward and away from the power booster with brake lines attached. 3. Disconnect the three hydraulic lines at the booster. Remove the retainer and washer at the brake pedal, inside the vehicle. 4. Remove the four nuts attaching the booster to the firewall from inside the vehicle and remove it. Remove the gasket. To install: 5. Position the booster on the dash panel over the gasket and install the four mounting nuts onto the firewall from inside the vehicle. Torque to 15 ft. lbs. (20 Nm). Install the pedal rod washer and retainer. 6. Position the master cylinder to the hydro-booster, install the mounting nuts, and torque to 20 ft. lbs. (27 Nm). 7. Install the three hydraulic lines, torquing the two high pressure lines (which are screwed in) to 20 ft. lbs. (27 Nm). 8. Install power steering fluid into the steering pump until fluid is at the base of the pump reservoir neck. 9. Disconnect the diesel injection pump 12V wire or the 12V wire to the distributor. THE ENGINE MUST NOT START. 10. Crank the engine for several seconds. Then, check the fluid level and replenish as necessary. 11. Connect wiring and start the engine. Turn the wheel from stop to stop two full times. Then, turn the engine off and depress the brake pedal five times to fully discharge the hydraulic accumulator. Check and if necessary replenish the hydraulic fluid. 12. Again start the engine and turn the wheel from lock to lock two full times. If there is visible foam in the power steering pump reservoir, wait an hour for it to dissipate (engine off). Then, replenish fluid. Fig. Fig. 1: Hydro-boost power booster mounting Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Master Cylinder REMOVAL & INSTALLATION Print See Figures 1, 2, 3, 4, 5 and 6 Vacuum Power Brakes On vacuum power brake equipped models, the master cylinder can be removed without removing the power vacuum cylinder from the vehicle. WARNING Only use flare nut wrenches when removing the brake lines from any component. Standard wrenches will damage the flare nut and line. 1. Clean the area around the master cylinder. 2. Disconnect the hydraulic lines at the master cylinder using flare nut wrenches only. Plug or tape the ends of the lines to prevent dirt from entering and to prevent fluid from leaking out. 3. Remove the master cylinder attaching nuts and remove the master cylinder. 4. Drain the master cylinder. CAUTION Be careful to keep brake fluid away from all body paint. The fluid acts like paint remover, and a few drops will quickly bubble any paint with which it comes in contact. Fig. Fig. 1: Master cylinder mounting on cars equipped with vacuum power brakes Fig. Fig. 2: Use a flare nut wrench when removing the brake lines Fig. Fig. 3: Use a pan to catch any brake fluid; be sure to tape or plug the lines after removing them from the master cylinder Fig. Fig. 4: The master cylinder attaching nuts can be removed after the lines have been disconnected Fig. Fig. 5: Removing the master cylinder from the vehicle Powermaster® Power Brakes This system uses an electrically operated hydraulic pump and an accumulator (pressure storage system) to provide power braking assist. CAUTION Because of the very high pressures used, always follow procedures very carefully, being especially sure to discharge the system prior to disconnecting anything. 1. Disconnect the negative (-) battery cable. Turn the ignition switch off. Then, discharge all pressure from the system by applying the brake pedal with maximum force (50 lbs. or more) at least 10 full strokes. 2. Disconnect the electrical connector from the pressure switch, located at the rear of the master cylinder on top. 3. Disconnect the electrical connector from the front of the pump, located under the master cylinder. 4. Disconnect the brake and hydraulic pressure pipes at the master cylinder and tape or cap the openings. Use a flare nut wrench only. 5. Remove the two attaching nuts. Pull the clevis pin out of the linkage to the brake pedal. Remove the unit. To install: 6. Position the unit onto the firewall and torque the mounting nuts to 22-30 ft. lbs. (30-41 Nm) and the brake pipe nuts to 10-13 ft. lbs. (14-17 Nm). 7. Connect the brake and hydraulic pressure pipes at the master cylinder using a flare nut wrench. 8. Connect the electrical connector to the front of the pump, located under the master cylinder. 9. Connect the electrical connector to the pressure switch, located at the rear of the master cylinder on top. 10. Bleed the system as described in the System Bleeding procedures in this section. Fig. Fig. 6: Powermaster® master cylinder mounting OVERHAUL See Figures 7, 8, 9, 10, 11, 12, 13 and 14 Except Powermaster® The models covered in this guide are equipped with either Moraine or Bendix master cylinders. The rebuilding kits may differ slightly, but the procedures are the same. Follow the instructions that come with each particular kit. Overhaul procedures for power brake master cylinders and manual brake master cylinders is the same. Note the procedure below for Powermaster® units. 1. Remove the master cylinder from the vehicle. 2. Remove the mounting gasket and boot, and the main cover, and purge the unit of its fluid. 3. Secure the cylinder in a vise and remove the pushrod retainer and secondary piston stop bolt found inside the forward reservoir (Moraine iron cylinder only). The plastic composite master cylinder reservoir can be removed by prying against the cylinder and reservoir. Work the reservoir from the rubber grommets using care not to damage either component. 4. Compress the retaining (lock) ring and extract it along with the primary piston assembly from the end of the bore. 5. Blow compressed air into the piston stop screw hole, if equipped, to force the secondary piston, spring, and retainer from the bore of the cylinder. An alternative method is to use hooked wire to snag and extract the secondary piston. 6. Check the bass tube fitting inserts and if they are damaged, remove them. Leave undamaged inserts in place. 7. If replacement is necessary, thread a 3 / 16 in. × 5 / 8 in. self-tapping screw into the insert. Hook the end of the screw with a claw hammer and pry the insert free. 8. An alternative way to remove the inserts is to first drill the outlet holes to over the hole to serve as a spacer, and then thread a 1 / 4 in.-20 × 3 13 / 64 in. and thread them with a 1 / 4 in.-20 tap. Position a thick washer / 4 in. hex head bolt into the insert and tighten the bolt until the insert is freed. 9. Use denatured alcohol and compressed air to clean the parts. Slight rust may be removed with crocus cloth. Never use petroleum-based solvents to clean brake parts. Also, a brake hone is helpful in removing varnish and slight rust. To assemble: 10. Replace the brass tube inserts by positioning them in their holes and threading a brake line tube nut into the outlet hole. Turn down the nut until the insert is seated. 11. Check the piston assemblies for correct identification and, when satisfied, position the replacement secondary seals in the twin grooves of the secondary piston. 12. The outside seal is correctly placed when its lips face the flat end of the piston. 13. Slip the primary seal and its protector over the end of the secondary piston opposite the secondary seals. The flat side of this seal should face the piston's compensating hole flange. 14. Replace the primary piston assembly with assembled pieces in the overhaul kit. 15. Moisten the cylinder bore and the secondary piston's inner and outer seals with clean brake fluid. Assemble the secondary piston spring to its retainer and position them over the end of the primary seal. 16. Insert the combined spring and piston assembly into the cylinder and use a small wooden dowel or pencil to seat the spring against the end of the bore. 17. Moisten the primary piston seals with brake fluid and push it, pushrod receptacle end out, into the cylinder. 18. Keep the piston pushed in and snap the retaining (lock) ring into place. 19. Relax the pressure on the pistons and allow them to seek their static positions. 20. Replace the secondary piston stop screw and torque it to 25-40 inch. lbs. (3-4 Nm), if so equipped. 21. Replace the reservoir diaphragm and cover. 22. Install the master cylinder and bleed the entire system. Fig. Fig. 7: Iron reservoir master cylinder Fig. Fig. 8: Removing the plastic master cylinder reservoir Fig. Fig. 9: It may be helpful to slightly depress the piston when removing the lock ring Fig. Fig. 10: Removing the primary piston from the master cylinder Fig. Fig. 11: Removing the secondary piston Fig. Fig. 12: Seals can be removed from the piston with a small pick or awl Fig. Fig. 13: Internal components of a master cylinder Powermaster® Units CAUTION The Powermaster® master cylinder unit must be overhauled on a clean bench. Be especially careful that there are no traces of ordinary, mineral type lubricants, as these will ruin the seals. 1. Remove the reservoir cover and diaphragm. Drain all brake fluid. 2. Remove: A. The pressure switch and O-ring. B. Accumulator and O-ring C. Electro-hydraulic pump and pressure hose assembly D. The sump hose clamps and the sump hose. E. The tube and nut assembly that runs from the sump hose to the master cylinder. F. Remove the two pump brackets from the master cylinder. CAUTION Do not scratch or deform in any way the outside diameter and sealing surface at the pushrod end of the power piston assembly. Also avoid such damage to the bores of the Powermaster® body. 3. Remove the retainer (it resembles a piston ring) from the groove in the rear of the unit. Then, pull the pushrod to remove the boot, retainer, pushrod and power piston group. 4. Remove the retainer, boot, pushrod, socket group, and piston guide from the power piston assembly. 5. Remove the O-ring from the piston guide. Then, remove the O-rings from the power piston assembly and piston guide. 6. Remove the reaction body group from the power piston assembly. 7. Remove the reaction piston and reaction disc from the reaction body group. CAUTION Do not disassemble the reaction body group or power piston assembly any further! If either are damaged, they must be replaced only as complete assemblies. 8. Use compressed air cautiously, building pressure slowly, to remove the primary and secondary piston assemblies. Direct the air pressure into the outlet port at the blind end of the master cylinder body. Block the port at the other end of the body. 9. Remove the secondary seal, spring retainer, and primary seal from the secondary piston. 10. Remove the spring from the master cylinder body bore. 11. Mount the master cylinder in a vise with the outboard side upward, clamping the assembly by the mounting flange located at the rear, and not the body itself . Then, carefully pry the reservoir off the body with a prybar. 12. Remove the reservoir grommets. Then, gently tap an Easy-Out® type threaded remover tool into the bore of the valve seat. Pull the tool straight out and remove the seat and seal. Discard the seat. 13. Remove the poppet and spring and discard the spring. To assemble: 14. Clean all parts except the pressure switch and electro-hydraulic pump in denatured alcohol. If necessary, wipe external surfaces of the pressure switch and electro-hydraulic pump clean with a cloth dampened slightly in denatured alcohol. 15. Inspect all metal parts for cracks, distortion or other damage. Inspect the primary piston sealing surfaces for scoring, deep scratches, or other damage where the damage could cause leaks. Replace the assembly if any of these defects are found. 16. Inspect the power piston and master cylinder bores for scoring or corrosion. Replace the assembly if either problem is noted. CAUTION Do not attempt to use an abrasive means to clean up these bores, or dangerous driving conditions could result! Use clean, fresh brake fluid to lubricate all parts at sliding surfaces prior to assembly. Lubricate O-rings, grommets, and seals with the same fluid (all should be replaced). Lubricate both the master cylinder and power piston bores with the same fluid prior to installing the piston assemblies into these bores. 17. Install a new spring and poppet into the body of the Powermaster® unit. Then, install a new valve seat and seal. Bottom these out by threading the nut of the nut and tube assembly into the body port. 18. Remove the assembly from the vise. Install the three grommets (of two different sizes) into the top of the body making sure they are fully seated . Then, lay the reservoir down on its upper surface and install the master cylinder onto the reservoir from above, holding it upside down. 19. Install the remaining internal components in reverse order. When installing the retainer for the power piston group, depress the piston guide and power piston. Bench bleed the master cylinder side of the unit by filling the reservoirs and working the pistons back and forth. 20. Install the brackets with the mounting bolts. Install the sump hose, clamps, and hydraulic tube. Install the electro-hydraulic pump and pressure hose and clamp. 21. Install the accumulator and O-ring. Install the pressure switch and O-ring. 22. Install the master cylinder in the vehicle and make all connections as described above. 23. Fill both sides of the reservoir with clean, fresh brake fluid meeting the standards shown on the reservoir cover. Then, turn the ignition switch on. Time the running of the pump with your watch. It must not run more than 20 seconds. Have an assistant shut the ignition switch off after 20 seconds if the pump does not cycle off by itself. With the pump running, the fluid level in the booster side of the reservoir should drop. If necessary, add just enough brake fluid to keep the reservoir pump port covered and ensure an adequate supply of air-free fluid to the pump. 24. When the pump stops, check to make sure fluid does not flow back into the reservoir from the booster and check for leaks from the reservoir. 25. Install the reservoir cover securely. Then, pump the brake pedal fully 10 times. Remove the reservoir cover and fill the reservoir to the full line. Again, turn the ignition switch on and time the operation of the pump. It should not run more than 20 seconds. Make sure fluid remains above the level of the reservoir pump port. Again, install the reservoir cover. 26. Turn the ignition switch on and then apply and release the brake pedal to cycle the pump on and off. Count the cycles and repeat the process until the total reaches 15. Make sure the pump does not run more than 20 seconds each cycle (turn the key off if necessary). Recheck the fluid levels and replenish. Check that the pump does not cycle on and off unless you apply the brakes. 27. Install the assembly onto the vehicle and bleed the entire system. Fig. Fig. 14: Exploded view of a Powermaster® master cylinder Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Vacuum Power Booster REMOVAL & INSTALLATION Print See Figure 1 1. Disconnect the negative (-) battery cable. Disconnect the booster pushrod from the brake pedal arm by removing the retaining clip, and sliding the eyelet end of the pushrod off of the pin on the brake arm. 2. Disconnect the master cylinder from the booster. 3. Remove the attaching nuts and remove the booster from the firewall. To install: 4. Install the booster to the firewall and torque the booster-to-firewall attaching nuts to 22-33 ft. lbs. (29-45 Nm). Reconnect the pushrod at the brake arm. 5. Install the master cylinder and bleed the system if the brake lines had to be disconnected. Fig. Fig. 1: Vacuum power booster mounting Back to Top Body & Trim GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Antenna REPLACEMENT Print See Figure 1 Fixed 1. Remove the steel antenna out of the base and masking tape the front edge of the right door. 2. Using a antenna bezel socket, loosen the bezel nut at the top of the fender. 3. Remove the side mounting bolt and disconnect the antenna lead at the junction. 4. Raise the vehicle and support with jackstands. 5. Remove the lower fender-to-body bolt and rocker panel molding screws. 6. Remove the inner fender and block. 7. Remove the bezel and the antenna base assembly. To install: 8. Install the antenna assembly and loosely tighten the bezel nut. 9. Install the inner fender screws, rocker panel molding screws and lower fender-to-body bolt. 10. Lower the vehicle. 11. Connect the antenna leads and tighten the bezel nut using the bezel socket J28641 or equivalent. Install the side mounting bolt. Power 1. Disconnect the negative battery cable. 2. Protect the door with masking tape and remove the five outer-to-inner fender panel screws. 3. Remove the lower fender-to-body bolt and rocker panel molding screws. 4. Remove the three fender-to-inner fender screws along the rear half of the wheel opening. 5. Remove the antenna bezel nut using a bezel nut socket tool J28641 and disconnect the electrical wiring. 6. Block the lower edge of the fender out, remove the antenna bracket screw and remove the antenna assembly. To install: 7. Install the antenna, gasket and bezel nut. Do NOT tighten at this time. 8. Install the mounting bolts. Do NOT tighten at this time. 9. Torque the bezel using the bezel socket and the lower mounting bolts. 10. Connect all antenna leads. 11. Install the fender bolts and screws. 12. Connect the negative battery cable and check operation. Fig. Fig. 1: Power antenna assembly Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Bumpers REMOVAL & INSTALLATION Print See Figures 1, 2, 3, 4, 5, 6 and 7 Front 1. Raise the vehicle and support with jackstands. 2. Disconnect the parking lamp connectors. 3. With the aid of an assistant, remove the eight bumper reinforcement-to-energy absorber nuts and remove the bumper. Note the size and position of the shims if used. To install: 4. With an assistant, install the bumper shims and nuts only hand tight. 5. Move the bumper from side to side to gain sideward adjustment. Add or subtract shims to gain in or out adjustment. Torque the retaining nuts to 18 ft. lbs. (24 Nm). 6. Connect the parking lamp wires and lower the vehicle. Fig. Fig. 1: Front bumper assembly, all models similar Fig. Fig. 2: Buick front bumper alignment Fig. Fig. 3: Oldsmobile front bumper alignment Fig. Fig. 4: Pontiac front bumper alignment Rear 1. Raise the vehicle and support with jackstands. 2. Disconnect the license plate lamp connectors. 3. With the aid of an assistant, remove the eight bumper reinforcement-to-energy absorber nuts and remove the bumper. Note the size and position of the shims if used. To install: 4. With an assistant, install the bumper shims and nuts only hand tight. 5. Move the bumper from side to side to gain sideward adjustment. Add or subtract shims to gain in or out adjustment. Torque the retaining nuts to 18 ft. lbs. (24 Nm). 6. Connect the license plate lamp wires and lower the vehicle. Fig. Fig. 5: Rear bumper assembly, all models similar Fig. Fig. 6: Sedan rear bumper alignment Fig. Fig. 7: Station wagon rear bumper alignment Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Doors REMOVAL & INSTALLATION Print See Figure 1 CAUTION Removing a door is a simple operation, but it requires careful handling of a heavy object that is awkward to handle. You must have a helper who will hold the door and ensure that it does not get out of control, which could hurt someone or strip the threads of the mounting bolts. Put a floor jack or other adjustable means of holding the door underneath before starting, so that the helper must only keep the door from tipping as you remove the fasteners. The easiest and best way to remove the door is to remove the bolts that fasten the door assembly to the hinges, rather than attempting to remove the bolts fastening the hinges to the body. This is true because it is much easier to gain access to these bolts. 1. If the vehicle has power operated components in the doors (electric windows or motor operated mirrors), disconnect the negative battery cable, remove the trim panel (see the appropriate procedure later in this section), and lift the watershield out far enough to reach the electrical connectors. Then, disconnect these connectors. Detach the rubber wire conduit and pull the harness coming from the body out of the door. 2. Very precisely use a sharp scribe to mark the relationship between the door and the door hinges so that you can remount it without the need to adjust it. 3. Open the door all the way and, with the help of another person and using a floor jack or other means, support the door. 4. Remove both the upper and lower bolts attaching the door to the outer portions of the hinges. Remove the door. To install: 5. Install the mounting bolts and turn them in until they are nearly ready to clamp the hinge to the door. 6. Position the door carefully so that the matchmarks line up. 7. Tighten the bolts alternately top and bottom until the door is tightly held in position. Torque the bolts to 15-21 ft. lbs. (20-28 Nm). 8. Install and connect all disconnected wiring and battery cable. Fig. Fig. 1: Door hinge bolt locations ADJUSTMENT Doors are adjustable by using floating plates inside both the doors and hinge pillars. Always mark locations of bolts before loosening them and beginning adjustment. It is best to remove the door lock striker to permit the door to hang free and then close the door so you can observe exactly how it fits onto the body. Front Doors 1. If the door requires fore and aft or up or down adjustment, loosen the body hinge pillar adjustments. Shift the position of the door with the help of an assistant and a floor jack. Then, tighten the bolts. When the position fore and aft and up and down is correct, torque the bolts to 15-21 ft. lbs. (20-28 Nm). If you have to move the door to the rear, replace the door jamb light switch. 2. If the door must be adjusted in or out, loosen the bolts attaching the door at the hinge pillar attachments. Shift the position of the door with the help of an assistant and a floor jack. Then, tighten the bolts. When the position in or out is correct, torque the bolts to 15-21 ft. lbs. (20-28 Nm). Rear Doors 1. If the door requires in or out or significant up or down adjustment, loosen the door side hinge attaching screws. Shift the position of the door with the help of an assistant and a floor jack. Then, tighten the bolts. When the position in or out and up and down is correct, torque the bolts to 15-21 ft. lbs. (20-28 Nm). 2. If the door requires fore or aft or a slight up or down adjustment, loosen the body side, center pillar hinge adjusting bolts. Shift the position of the door with the help of an assistant and a floor jack. Then, tighten the bolts. When the position is correct, torque the bolts to 15-21 ft. lbs. (20-28 Nm). If you have to move the door to the rear, replace the door jamb light switch. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide EXTERIOR Print WARNING If equipped with the air cushion restraint system, do not attempt any adjustment, repair or removal of any portion of the chassis sheet metal which would require removal or disconnecting of the bumper impulse detector until the ignition switch is turned to the LOCK position and the negative battery cable is disconnected and the end taped. This procedure must be followed to prevent accidental deployment of the system which could result in personal injury and/or damage to the systems components. In addition, care must be exercised to never bump or strike the bumper impulse detector in a manner which could cause inadvertent deployment or improper operation of the system. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Fenders Fenders are adjustable with shims. To add or remove shims, loosen the bolts at the shim locations and carefully apply force with a prybar to provide clearance for adding or removing shims. Tape fender and door edges with masking tape to prevent damage during replacement. REMOVAL & INSTALLATION See Figures 1, 2, 3, 4, 5, 6, 7 and 8 1975 and 1976 1. Disconnect the negative battery cable then the positive cable. 2. Tape the fender and the door edge. 3. Disconnect the side marker lamp wires. 4. Remove the tie bar to front end panel seal. 5. Disconnect the headlamp wires. 6. Remove the tie bar to fender brace. 7. Remove the cowl to fender brace. 8. Remove the dash to fender top bolt. 9. Remove the hood hinge from the fender and block the hood. 10. Remove the fender to support bolts. 11. Remove the fender to cowl bolts. 12. Remove the fender and filler plate. 13. Remove the fender from the filler plate. 14. Installation is the reverse of removal. Fig. Fig. 1: 1975 and 1976 fender attachment, all models similar Print Fig. Fig. 2: 1975 and 1976 filler plate attachment, all models similar 1977 to 1990 1. Disconnect the negative battery cable. 2. Remove the hood and hood hinges. 3. Remove the fender bolt from the battery ground strap, if applicable. 4. Remove the battery and battery tray if they are located on the side to be replaced. 5. Remove any components mounted on the wheel housing/fender assembly on the side to be replaced. 6. Remove the cowl to fender bolts and shims. Note the position and number of shims used. 7. Remove the body to fender bolts. 8. Remove the fender extension bolts. 9. Remove the bolt from the frame brace to fender, if equipped. 10. Remove the bumper filler attaching bolts. 11. Remove the wheelhousing to radiator support bolts. 12. Remove the front end panel to fender bolts. 13. Disconnect the side marker lamp electrical connections. 14. Remove the front fender and wheelhousing with the aid of a helper. 15. Installation is the reverse of removal. Fig. Fig. 3: Front fender-to-body attachment, 1977 to 1990 Fig. Fig. 4: Buick and Oldsmobile front fender-to-radiator support attachment, 1977 to 1990 Fig. Fig. 5: Pontiac front fender-to-radiator support attachment, 1977 to 1990 Fig. Fig. 6: Buick front end panel dimensions Fig. Fig. 7: Oldsmobile front end panel dimensions Fig. Fig. 8: Pontiac front end panel dimensions Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Grille REMOVAL & INSTALLATION Print See Figures 1, 2 and 3 Buick 1. Remove the two grille return springs, radiator grille nuts and grille. 2. Install the grille, torque the nuts to 97 inch lbs. (11 Nm) and install the return springs. Fig. Fig. 1: Buick grille Oldsmobile and Pontiac 1. Remove the radiator grille bolts, grille and baffle if equipped. 2. Install the grille, baffle and bolts. Torque the bolts to 13 inch lbs. (1.5 Nm). Fig. Fig. 2: Oldsmobile grille Fig. Fig. 3: Pontiac grille Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Hood REMOVAL & INSTALLATION Print See Figures 1 and 2 1. Raise the hood. Cover the fenders with protective pads. This is necessary to protect the paint because the hood will often contact these areas during removal or installation procedures. Place masking tape on the fender and hood covers and edges. 2. On models equipped with an underhood light disconnect the lamp wiring. 3. Very precisely use a sharp scribe to mark the relationship between the hood and the hood hinges so that you can remount it without the need to adjust it. 4. Support the hood, especially at the front, in a secure manner. Remove the bolts on either side that fasten the tops of the hinges to the underside of the hood. Remove the bolts starting at the front and moving toward the rear to help avoid placing stress on the assembly. Make sure the hood is securely supported to help prevent bending of it as you work. 5. When all the bolts are removed, lift the rear of the hood off the hinges and then lift the unit off the vehicle. To install: 6. Carry the hood from either side and position it over the engine compartment in its normal position. Raise the front and position it at the right angle to the upper surfaces of the hinges. Pass all the bolts through the upper hinges and start them into the lower side of the hood. Do not tighten them, but leave plenty of clearance to adjust the position of the hood on the hinges. 7. Carefully shift the hood on both hinges simultaneously to align the matchmarks. Then, tighten the mounting bolts, torquing to 20 ft. lbs. (27 Nm). Close the hood and check its fit in the body and the alignment of the hood latch. If necessary, readjust the hood alignment as described below. Reconnect the underhood light wiring, if the vehicle is so equipped. Fig. Fig. 1: A hood and related components, all models similar Fig. Fig. 2: Hood mounting, all models similar ALIGNMENT Close the hood and check its fit in the body and the alignment of the hood latch. If necessary, loosen all the mounting bolts just slightly and shift the adjustment in the correct direction. Repeat this procedure until the hood latches smoothly and securely and all gaps between the hood and body are of equal width. Torque the mounting bolts to 20 ft. lbs. (27 Nm). Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Outside Mirrors REMOVAL & INSTALLATION Print 1. Disconnect the negative battery cable. 2. Remove the door trim panel, sound deflector and peel back the water shield as outlined in this information. 3. Remove the remote mirror control and cable from the instrument panel. If power mirrors, disconnect the electrical connector. 4. Disconnect the control cable guide clips from inside the door. 5. The window has to be down. Remove the two mirror-to-door retaining nuts and mirror. To install: 6. Thread the control cable or wire through the access hole, install the mirror and insulator. 7. Reconnect the control cable or wiring to the retaining clips. 8. Install the water deflector, sound insulator and trim panel. 9. Install the remote control to the instrument panel. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Power Sunroof REMOVAL & INSTALLATION Print See Figure 1 1. Disconnect the negative battery cable. 2. Place the sunshade in the stowed position. 3. Move the sliding panel rearward until the front rollers on the sliding panel contact the bottom of the cable guide ramp (forward down position). 4. Remove the garnish moldings, coat hooks, map lamp retainer, and dome lamp. 5. Remove the sunroof opening headlining close-out lace. 6. Remove the headlining material from the headlining retainer. 7. Disengage and lower the headlining. 8. Disconnect the wire harness from the switch and the dome lamp, remove the headlining. 9. Remove the dome lamp retaining studs. 10. Remove the hoses from the housing. 11. Remove the screws from each of the rearmost side supports. 12. Remove the screws holding the housing to the front header. 13. Support the sunroof housing and remove the nuts from the side front screws that retain the housing to the roof supports. Lower and remove the sun roof housing. 14. Installation is the reverse of removal. Torque nuts at the side front locations to 7-10 ft. lbs. (10-14 Nm). Fig. Fig. 1: Exploded view of the sunroof assembly Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Station Wagon Tailgate REMOVAL & INSTALLATION Print See Figure 1 3 To perform this procedure, you will need a length of rod /16in. (5mm) in diameter and 12 in. (305mm) long. You will also need new, service hinge pins and retaining rings. 1. First, rotate the tailgate up and down until the torque rod tension has been eliminated. This occurs at a point near the vertical position of the gate, when spring tension is not required to keep the gate under control. You should be able to feel the point at which there is no longer significant weight to be supported as you raise the gate, and stop there. CAUTION Proceed carefully with the next step in case there is still some tension on the torque rod. 2. Mark the position of the torque rod assist link on the rear body pillar, and then remove it. 3. Open the tailgate and support it in the horizontal position. When the gate is securely supported, disconnect the support cables at the sides of the gate. 4. Place the length of rod against the point of one of the hinge pins. Strike the rod hard with a hammer to force the pin out of the hinge. You have to shear the retaining ring tabs to do this. Repeat this on the hinge on the other side. Then, remove the tailgate. To install: 5. Install new retaining rings in the grooves in the new hinge pins, positioning the rings so the tabs point toward the heads of the pins. To install, first align the gate to the body and so the hinge halves fit together properly. Then, tap the new hinge pins into position in the same direction in which the original pins were installed. Reverse the remaining procedures, installing the torque rod assist link in the same position, according to the markings made earlier. Fig. Fig. 1: Station wagon tailgate components ALIGNMENT Adjust the tailgate horizontally by loosening all the hinge-to-body bolts, repositioning the gate, and then retightening the bolts. Make sure to retain all the shims in position, unless the gate is too close to or too far from the body. If it is necessary to move the tailgate bottom in or out, loosen the hinge bolts and add or subtract shims between the hinge and body. Back to Top GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide Trunk Lid REMOVAL & INSTALLATION Print See Figure 1 1. Raise the trunk lid. Cover the fenders with some sort of protective pads. This is necessary to protect the paint because the trunk lid will often contact these areas during removal or installation procedures. 2. On models equipped with an underhood light disconnect the lamp wiring. 3. Very precisely use a sharp scribe to mark the relationship between the trunk lid and the hinges so that you can remount it without the need to adjust it. 4. Support the trunk lid, especially at the rear, in a secure manner. Remove the bolts on either side that fasten the sides of the hinges to the underside of the trunk lid. Remove the bolts starting at the rear and moving toward the front to help avoid placing stress on the assembly. Make sure the trunk lid is securely supported to help prevent bending of it as you work. 5. When all the bolts are removed, lift the rear of the trunk lid off the hinges and then lift the unit off the vehicle. To install: 6. Carry the trunk lid from either side and position it over the luggage compartment in its normal position. Raise the rear and position it at the right angle to the upper surfaces of the hinges. Pass all the bolts through the trunk lid and start them into the side of the upper hinges. Do not tighten them, but leave plenty of clearance to adjust the position of the trunk lid on the hinges. 7. Carefully shift the trunk lid on both hinges simultaneously to align the matchmarks. Then, tighten the mounting bolts, torquing to 20 ft. lbs. (27 Nm). Close the trunk lid and check its fit in the body and the alignment of the trunk lid latch. If necessary, readjust the alignment. Reconnect the underhood light wiring, if the vehicle is so equipped. Fig. Fig. 1: Trunk lid mounting ADJUSTMENT All adjustments (fore and aft and up and down) are made by loosening the hinge strap-to-lid attaching bolts. Loosen all the bolts before adjusting the position of the lid to avoid springing it and to make adjustment easier. Slide the hood back and forth, locating both sides as required; then tighten the bolts. No side-to-side adjustment is provided. If the hood has adjustable rear bumpers and it does not sit level, loosen the locknuts and turn the bumper screws up or down as necessary. Retighten the locknuts. You may find it helpful to close the trunk lid and measure the gap between the hood and body with a finely calibrated ruler. Back to Top