GM Bonneville/Eighty Eight/LeSabre 1986-1999

Intake Manifold

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REMOVAL & INSTALLATION




CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by 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. Coolant should be reused unless it is contaminated or several years old.

1986-90 Vehicles
3.8L (VIN 3) ENGINE

See Figure 1

  1. Relieve the pressure in the fuel system before disconnecting any fuel line connections. Refer to the procedure in Fuel System .
  2.  
  3. If not already done, disconnect the negative battery cable.
  4.  
  5. Remove the mass air flow sensor and air intake duct.
  6.  
  7. Remove the serpentine accessory drive belt, alternator and bracket.
  8.  
  9. Remove the ignition coil module, TV cable, throttle cable and cruise control cable.
  10.  
  11. Tag and disconnect all necessary vacuum hoses and electrical wiring.
  12.  
  13. Drain the cooling system into a suitable container. Disconnect the heater hoses from the throttle body and upper radiator hose.
  14.  
  15. Disconnect the fuel lines from the fuel rail and injectors.
  16.  
  17. Unfasten the intake manifold retaining bolts and remove the intake manifold and gasket.
  18.  



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Fig. Fig. 1: You must tighten the intake manifold bolts in the proper sequence - 3.8L (VIN 3) engine

To install:
  1. Clean the cylinder head and intake manifold surfaces from any foreign matter, nicks or heavy scratches.
  2.  
  3. Install the intake manifold gasket and rubber seals. Apply sealer 1050026 or equivalent, on the gasket. Apply sealer/lubricant 1052080 or equivalent, to all pipe thread fittings.
  4.  
  5. Carefully position the intake manifold on the cylinder block. Install the intake manifold bolts, then tighten them in sequence to 47 ft. lbs. (65 Nm).
  6.  
  7. Connect the fuel lines to the fuel rail and injectors.
  8.  
  9. Install the heater hoses to the throttle body and upper radiator hose.
  10.  
  11. Connect all vacuum hoses and electrical wiring, as tagged during removal.
  12.  
  13. Install the ignition coil module, TV cable, throttle cable and cruise control cable.
  14.  
  15. Install the bracket, alternator and serpentine belt.
  16.  
  17. Install the mass air flow sensor and air intake duct.
  18.  
  19. Connect the negative battery cable.
  20.  
  21. Fill cooling system and check for leaks. Start the engine and allow to come to normal operating temperature. Recheck for leaks. Check coolant level and add if necessary.
  22.  

3.8L (VIN C) ENGINE

See Figures 2 through 17

  1. Properly relieve the fuel system pressure, as outlined in Fuel System .
  2.  
  3. If not already done, disconnect the negative battery cable.
  4.  
  5. Disconnect the fuel lines from the fuel rail.
  6.  
  7. Place a clean drain pan under the radiator, open the draincock and drain the cooling system.
  8.  
  9. Remove the serpentine drive belt, alternator and bracket.
  10.  



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Fig. Fig. 2: Unfasten the 3 mounting bolts, then remove the alternator bracket (with the ignition coil attached)

  1. Disconnect the coolant bypass hose, the heater pipe and the upper radiator hose from the intake manifold.
  2.  



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Fig. Fig. 3: Disconnect the coolant bypass hose from the intake manifold



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Fig. Fig. 4: Detach the heater pipe from the intake manifold

  1. Remove the power steering pump and braces, and move them aside; do not disconnect the pressure lines.
  2.  



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Fig. Fig. 5: Unfasten the power steering pump brace retaining bolts



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Fig. Fig. 6: Remove the power steering pump brace

  1. Remove the vacuum hoses and tag and detach the electrical connectors from the intake manifold.
  2.  
  3. Remove the EGR pipe, EGR valve and adapter from the throttle body.
  4.  



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Fig. Fig. 7: The EGR pipe is located on the side of the front valve cover (see arrow)



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Fig. Fig. 8: Unfasten the hose clamp, then disconnect the EGR pipe

  1. Remove the throttle body coolant pipe, the throttle body and the throttle body adapter.
  2.  



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Fig. Fig. 9: Unfasten the throttle body adapter retaining bolts ...



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Fig. Fig. 10: ... then remove the throttle body adapter



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Fig. Fig. 11: Remove the throttle body adapter gasket

  1. Disconnect the rear spark plug wires. Unfasten the intake manifold-to-engine bolts and remove the manifold.
  2.  



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Fig. Fig. 12: Overview of the intake manifold and retaining bolt tightening sequence



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Fig. Fig. 13: Remove the intake manifold retaining bolts ...



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Fig. Fig. 14: ... then lift the manifold up and remove it from the vehicle

  1. Remove and discard the manifold gaskets and seals, then clean the gasket mating surfaces.
  2.  



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Fig. Fig. 15: Remove the intake manifold gaskets ...



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Fig. Fig. 16: ... and the seals from each end of the manifold



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Fig. Fig. 17: A piece of Scotchbrite®, or similar non-abrasive scouring pad, works well to clean the manifold gasket mating surfaces

To install:
  1. Install new gaskets and the proper sealant on the ends of the manifold seals.
  2.  
  3. Install the intake manifold and tighten the mounting bolts, in sequence, twice to 23 inch lbs. (10 Nm).
  4.  
  5. Connect the rear spark plug wires.
  6.  
  7. Install the throttle body adapter, throttle body and throttle body coolant pipe. Tighten the bolts to 20 ft. lbs. (27 Nm).
  8.  
  9. Install the EGR valve and adapter. Replace the EGR pipe.
  10.  
  11. Connect the vacuum hoses and the electrical connections to the intake manifold.
  12.  
  13. Install the coolant pipe, upper radiator hose and the upper bypass hose to the intake manifold.
  14.  
  15. Install the power steering pump and bracket assembly.
  16.  
  17. Install the alternator and bracket assembly. Replace the serpentine belt.
  18.  
  19. Refill the cooling system and connect the negative battery cable. Start the engine, allow it to reach normal operating temperatures and check for leaks.
  20.  

1991-97 Vehicles

EXCEPT 1995-97 VIN 1 AND K ENGINES

See Figures 18 and 19

  1. Remove the plastic engine cover and air intake duct.
  2.  
  3. Properly relieve the fuel system pressure, as outlined in Fuel System of this repair guide. If not already done, disconnect the negative battery cable.
  4.  
  5. Tag and disconnect the spark plug wires on the right side of the engine and set aside.
  6.  
  7. Remove the fuel rail from the vehicle.
  8.  
  9. Remove the exhaust crossover heat shield.
  10.  
  11. Unfasten the cable bracket-to-cylinder head mounting bolt.
  12.  
  13. Remove the power steering pump bracket.
  14.  
  15. Loosen the alternator mounting bolts, then position the alternator aside for clearance.
  16.  
  17. Remove the alternator bracket.
  18.  
  19. Disconnect the heater pipes and bypass hose.
  20.  
  21. Unfasten the retaining bolts, then remove the intake manifold from the vehicle. Remove and discard the gasket and thoroughly clean the gasket mating surfaces and intake manifold bolts and bolt holes.
  22.  



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Fig. Fig. 18: Exploded view of the intake manifold and gaskets - 12763.8L (VIN C) engine shown, later models similar



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Fig. Fig. 19: Intake manifold bolt tightening sequence - 1276-95 vehicles

To install:
  1. Apply a suitable sealer to the ends of the manifold seals.
  2.  
  3. Position a new intake manifold gasket, then place the intake manifold over it. Apply a suitable threadlocking sealer to the retaining bolts, then install and tighten them twice, in the sequence shown in the accompanying figure, to 23 inch lbs. (10 Nm).
  4.  
  5. Connect the bypass hose and the heater pipes.
  6.  
  7. Install the alternator bracket. Move the alternator into position, then tighten the mounting bolts.
  8.  
  9. Install the power steering pump bracket.
  10.  
  11. Tighten the cable bracket-to-cylinder head mounting bolt.
  12.  
  13. Install the exhaust crossover heat shield.
  14.  
  15. Install the fuel rail in the vehicle.
  16.  
  17. Connect the right side spark plug wires, as tagged during removal.
  18.  
  19. Connect the negative battery cable.
  20.  
  21. Install the air intake duct and engine cover.
  22.  

1995-97 VIN K ENGINE

See Figures 19, 20 and 21

On these engines, the upper and lower intake manifolds must be removed separately.

  1. Properly relieve the fuel system pressure, as outlined in Fuel System of this repair guide.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Drain the cooling system into a suitable container.
  6.  
  7. Remove the fuel injector sight shield and air intake duct.
  8.  
  9. Tag and disconnect the spark plug wires on the right side of the engine and position aside.
  10.  
  11. Remove the manifold vacuum source.
  12.  
  13. Remove the fuel rail.
  14.  
  15. Remove the EGR heat shield.
  16.  
  17. Unfasten the cable bracket-to-cylinder head mounting bolt.
  18.  
  19. Disconnect the throttle cable.
  20.  
  21. Remove the throttle body support bracket.
  22.  
  23. Unfasten the upper intake manifold bolts, then remove the upper manifold.
  24.  

This engine has two bolts which are hidden beneath the upper intake. These bolts are located in the right front and left rear corners of the lower intake manifold. This is why it is necessary to remove the upper before servicing the lower manifold.

  1. Disconnect the upper radiator hose.
  2.  
  3. Remove the alternator, as outlined in Engine Electrical of this repair guide.
  4.  
  5. Remove the drive belt tensioner.
  6.  
  7. Remove the EGR valve outlet pipe.
  8.  
  9. Unfasten the intake manifold bolt, then remove the manifold from the vehicle. Remove and discard the gaskets. Thoroughly clean the gasket mating surfaces, intake manifold bolts and bolt holes.
  10.  

To install:
  1. Position a new gasket, then place the lower intake manifold over it. Apply a suitable threadlocking compound to the bolts, then install them. For 1995 vehicles, tighten the bolts twice, to 24 inch lbs. (10 Nm), in the sequence shown in the accompanying figure. For 1996-97 vehicles, tighten the bolts to 1 ft. lbs. (15 Nm), in the sequence shown in the accompanying figure.
  2.  



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Fig. Fig. 20: Exploded view of the upper and lower intake manifold and gaskets - 1995 3.8L (VIN K) engine



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Fig. Fig. 21: Intake manifold bolt tightening sequence - 1996-97 3.8L (VIN K) engine; VIN 1 similar

  1. Install the EGR valve outlet pipe.
  2.  
  3. Install the drive belt tensioner.
  4.  
  5. Install the alternator.
  6.  
  7. Connect the upper radiator hose.
  8.  
  9. Position the upper intake manifold on the lower manifold. Install the retaining bolts and tighten to 24 inch lbs. (10 Nm).
  10.  
  11. Install the throttle body support bracket, then connect the throttle cable.
  12.  
  13. Install the cable bracket-to-cylinder head mounting bolt.
  14.  
  15. Install the EGR heat shield.
  16.  
  17. Install the fuel rail.
  18.  
  19. Install the manifold vacuum source.
  20.  
  21. Connect the right side spark wires on the right side of the engine.
  22.  
  23. Install the fuel injector sight shield and air intake duct.
  24.  
  25. Fill the cooling system with the proper type and amount of fluid.
  26.  
  27. Connect the negative battery cable. Start the engine and check for leaks. Check the cooling system, and add as necessary.
  28.  

1995 VIN 1 ENGINE
  1. Properly relieve the fuel system pressure, as outlined in Fuel System of this repair guide.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Drain the cooling system into a suitable container.
  6.  
  7. Remove the fuel injector sight shield and air intake duct.
  8.  
  9. Tag and disconnect the spark plug wires from the right side of the engine and position it aside.
  10.  
  11. Remove the manifold vacuum source.
  12.  
  13. Disconnect the fuel feed and return lines.
  14.  
  15. Disconnect the upper radiator hose and bypass hose.
  16.  
  17. Tag and detach the electrical connectors from the following components:
    1. EGR valve.
    2.  
    3. Throttle Position (TP) sensor.
    4.  
    5. Idle Air Control (IAC) solenoid.
    6.  
    7. Fuel injectors.
    8.  
    9. Manifold Air Pressure (MAP) solenoid.
    10.  

  18.  
  19. Disconnect the EGR outlet pipe.
  20.  
  21. Detach the throttle and cruise cables.
  22.  
  23. Unbolt the throttle bracket with the power steering reservoir and position aside.
  24.  
  25. Remove the inner accessory drive belt.
  26.  
  27. Disconnect the heater hose pipe from the intake manifold.
  28.  
  29. Remove the tensioner bracket-to-supercharger retaining stud using the standard double nut procedure.
  30.  
  31. Unfasten the intake manifold bolts, then remove the intake manifold from the vehicle. If equipped, remove and discard the intake manifold gasket. Thoroughly clean the gasket mating surfaces, bolts and bolt holes.
  32.  

To install:
  1. Apply a suitable sealer to the ends of the manifold seals.
  2.  
  3. Position a new intake manifold gasket. Apply a suitable threadlocking compound to the threads of the intake manifold bolts.
  4.  
  5. Install the intake manifold, then secure with the mounting bolts. Tighten the bolts to 1 ft. lbs. (15 Nm).
  6.  
  7. Install the tensioner bracket.
  8.  
  9. Connect the heater hose pipe to the intake.
  10.  
  11. Install the inner accessory drive belt.
  12.  
  13. Place the throttle bracket, with the power steering reservoir, in position and secure with the retainers.
  14.  
  15. Connect the throttle and cruise cables.
  16.  
  17. Attach the EGR outlet pipe.
  18.  
  19. Attach the electrical connectors to the following components, as tagged during removal:
    1. MAP sensor.
    2.  
    3. Fuel injectors.
    4.  
    5. Idle Air Control (IAC) solenoid.
    6.  
    7. TP sensor.
    8.  
    9. EGR valve.
    10.  

  20.  
  21. Connect the upper radiator hose and bypass hose.
  22.  
  23. Attach the fuel feed and return lines.
  24.  
  25. Fill the cooling system with the proper type and amount of coolant.
  26.  
  27. Install the manifold vacuum source.
  28.  
  29. Connect the spark plug wires on the right side of the engine, as tagged during removal.
  30.  
  31. Install the fuel injector sight shield and air intake duct.
  32.  
  33. Connect the negative battery cable.
  34.  

1996-97 3.8L (VIN 1) Engine
  1. Disconnect the negative battery cable.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. Remove the front splash shield.
  6.  
  7. Drain the engine coolant into a suitable container. Don't forget to close the radiator draincock.
  8.  
  9. Install the front splash shield.
  10.  
  11. Carefully lower the vehicle.
  12.  
  13. Remove the supercharger, as outlined in this section.
  14.  
  15. Remove the thermostat housing.
  16.  
  17. Disconnect the EGR tube from the intake manifold.
  18.  
  19. Detach the electrical connection from the temperature sensor.
  20.  
  21. Unfasten the retainers, then remove the intake manifold from the vehicle. If equipped, remove and discard the intake manifold gasket. Thoroughly clean the gasket mating surfaces, bolts and bolt holes.
  22.  

To install:
  1. Position a new gasket or seal(s), as applicable, then install the intake manifold. Install a suitable threadlocking compound to the intake manifold bolts. Install the bolts and tighten to 1 ft. lbs. (15 Nm), in the sequence shown in the accompanying figure.
  2.  
  3. Attach the electrical connector to the temperature sensor.
  4.  
  5. Connect the EGR tube to the intake manifold.
  6.  
  7. Install the thermostat housing.
  8.  
  9. Install the supercharger, as outlined in this section.
  10.  
  11. Fill the cooling system with the proper type and amount of coolant.
  12.  
  13. Connect the negative battery cable, then start the engine and check for leaks. Check the coolant level and add if necessary.
  14.  

1998-99 Vehicles

See Figures 22 through 29

  1. Properly relieve the fuel system pressure, as outlined in Fuel System of this repair guide.
  2.  
  3. If not done already, disconnect the negative battery cable.
  4.  
  5. Drain the engine cooling system into a suitable container.
  6.  
  7. Tag and disconnect the right side spark plug wires, then position them aside.
  8.  



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Fig. Fig. 22: Disconnect the right side spark plugs, then position the harness aside

  1. Detach the spark plug wires from the fuel injector rail.
  2.  
  3. Unfasten the fuel lines from the fuel rail. Remove the mounting nuts, then remove the fuel rail from the engine.
  4.  
  5. Remove the accelerator control cable bracket bolts, then remove the cable bracket from the manifold.
  6.  



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Fig. Fig. 23: Remove the bolts, then remove the accelerator control cable bracket

  1. Unfasten the throttle body nuts, then remove the throttle body. Remove the throttle body gasket.
  2.  



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Fig. Fig. 24: Exploded view of the throttle body mounting

The two bolts which hold the lower intake manifold to the cylinder head are only accessible after the upper intake manifold is removed. The bolts are found in the right front and left rear corners of the lower intake manifold. You must remove the upper intake manifold to service the lower manifold.

  1. Unfasten the upper intake manifold bolts and stud, then remove the upper manifold.
  2.  



Click image to see an enlarged view

Fig. Fig. 25: Exploded view of the upper intake manifold mounting

  1. Remove the EGR outlet pipe from the intake manifold.
  2.  
  3. Unfasten the lower intake manifold bolts, then remove the lower manifold and gasket.
  4.  



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Fig. Fig. 26: Removing the lower intake manifold and gasket - VIN K engine shown, VIN 1 similar

  1. Thoroughly clean the gasket mating surfaces, bolt and bolt holes.
  2.  

To install:
  1. Position the lower manifold gasket. Install the lower intake manifold.
  2.  
  3. Apply a suitable threadlocking compound to the lower manifold bolts. Install the bolts, including the 2 hidden bolts, and tighten to 1 ft. lbs. (15 Nm), in the sequence shown in the accompanying figures.
  4.  



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Fig. Fig. 27: Lower intake manifold bolt tightening sequence - VIN K engine



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Fig. Fig. 28: Bolt tightening sequence for the lower intake manifold - VIN 1 engine

  1. Install the EGR outlet pipe to the intake manifold and secure with the mounting bolt. Tighten the bolt to 21 ft. lbs. (29 Nm).
  2.  
  3. Position a new upper intake manifold gasket, then place the upper manifold on the gasket.
  4.  
  5. Install the upper intake manifold bolts, then tighten the bolts to 89 inch lbs. (10 Nm), in the sequence shown in the accompanying figure.
  6.  



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Fig. Fig. 29: Upper intake manifold bolt tightening sequence

  1. Install the throttle body gasket and throttle body. Install the retaining nuts and tighten to 24 inch lbs. (10 Nm).
  2.  
  3. Install the engine wiring harness shield bracket and retaining bolt and nut. Tighten to 24 inch lbs. (24 Nm).
  4.  
  5. Install the accelerator control cable bracket. Secure with the bracket retaining bolts and tighten to 18 ft. lbs. (16 Nm).
  6.  
  7. Install the fuel rail and secure with the nuts. Tighten to 24 inch lbs. (10 Nm). Connect the fuel lines.
  8.  
  9. Place the right side spark plug wiring harness in position, then connect the wires as tagged during removal.
  10.  
  11. Fill the cooling system with the proper type and amount of coolant.
  12.  
  13. Connect the negative battery cable, then start the engine and check for leaks. Check the coolant level and add if necessary.
  14.  

 
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