GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2002 🢒 Century 🢒 Engine 🢒 Engine Mechanical - 3.1L 🢒 Lower Intake Manifold Replacement

Removal Procedure
  1. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  2. Remove the upper intake manifold. Refer to Upper Intake Manifold Replacement .
  3. Remove the left valve rocker arm cover. Refer to Valve Rocker Arm Cover Replacement - Left Side .
  4. Remove the right valve rocker arm cover. Refer to Valve Rocker Arm Cover Replacement - Right Side .

    5. Object Number: 190517 Size: SH
  5. Disconnect the engine coolant temperature (ECT) sensor electrical connector.

    6. Object Number: 190518 Size: SH
  6. Disconnect and remove the fuel injector and the manifold absolute pressure (MAP) sensor wiring harnesses.

    7. Object Number: 190512 Size: SH
  7. Remove the fuel pipe clip bolt.

    8. Object Number: 190511 Size: SH
  8. Remove the fuel pipe clip.

    9. Object Number: 190514 Size: SH
  9. Remove the fuel feed pipe from the fuel injector rail. Refer to Fuel Hose/Pipes Replacement - Filter to Engine in Engine Controls - 3.1L.

    10. Object Number: 190513 Size: SH
  10. Remove the fuel return pipe from the fuel injector rail. Refer to Fuel Hose/Pipes Replacement - Filter to Engine in Engine Controls - 3.1L.

    11. Object Number: 190516 Size: SH
  11. Remove the fuel injector rail. Refer to Fuel Injection Fuel Rail Assembly Replacement in Engine Controls - 3.1L.
  12. Remove the power steering pump from the front engine cover and reposition. Refer to Power Steering Pump Replacement in Power Steering System.

    13. Object Number: 190515 Size: SH
  13. Remove the heater inlet pipe with heater hose from the lower intake manifold and reposition.
  14. Remove the radiator inlet hose from the engine. Refer to Radiator Inlet Hose Replacement in Engine Cooling.

    15. Object Number: 190522 Size: SH
  15. Remove the thermostat bypass hose from the thermostat bypass pipe and lower intake manifold pipe.

    16. Object Number: 54281 Size: SH
  16. Remove the lower intake manifold bolts.
  17. Remove the lower intake manifold.
  18. Remove the valve rocker arms and pushrods. Refer to Valve Rocker Arm and Push Rod Replacement .

    19. Object Number: 61820 Size: SH
  19. Remove the lower intake manifold gaskets and seals.
  20. Clean the lower intake manifold gasket mating surfaces.
  21. Remove and clean all the RTV sealant from the lower intake manifold and the engine block (1).

    22. Object Number: 190519 Size: SH
  22. Remove the ECT sensor.

    23. Object Number: 190520 Size: SH
  23. Remove the water outlet bolts.
  24. Remove the water outlet.

    25. Object Number: 190521 Size: SH
  25. Remove the thermostat.

Installation Procedure

    Object Number: 190521 Size: SH
  1. Install the thermostat.

    2. Object Number: 190520 Size: SH
  2. Install the water outlet.

    3. Notice: Refer to Fastener Notice in the Preface section.

  3. Install the water outlet bolts.

    4. Tighten
    Tighten the bolts to 25 N·m (18 lb ft).


    Object Number: 190519 Size: SH
  4. Install the ECT sensor.

    5. Tighten
    Tighten the sensor to 23 N·m (17 lb ft).


    Object Number: 843417 Size: SH

    Important: All gasket-mating surfaces need to be free of oil, and foreign material. Use GM P/N 12346139 (Canadian P/N 10953463) or equivalent to clean surfaces.

  5. Install the lower intake manifold gaskets.
  6. With gaskets in place apply a small drop 8-10 mm (0.31-0.39 inch) of RTV Sealer GM P/N 12346141 (Canadian P/N 10953433) or equivalent to the 4 corners of the intake manifold to block joint (1).
  7. Connect the 2 small drops with a bead of RTV Sealer that is between 8-10 mm (0.31-0.39 inch) wide and 3.0-5.0 mm (0.10.20 inch) thick (2).
  8. Install the valve rocker arms and pushrods. Refer to Valve Rocker Arm and Push Rod Replacement .
  9. Install the lower intake manifold .

    10. Notice: Refer to Fastener Notice in the Preface section.


    Object Number: 187067 Size: SH

    Important: All lower intake manifold bolts need to be cleaned, free of any foreign material, and reused only if new bolts are unavailable. Use GM P/N 12345382 (Canadian P/N 10953489) or equivalent and apply to the old intake manifold bolt threads.

    Important: Manufacturer recommends the center bolts be fully torqued before the diagonal bolts to assure proper seal ability.

    Important: Lower intake manifold bolts in location 6 and 7 should be torqued to specification using a crows foot type tool.

  10. Install the lower intake manifold bolts.

    11. Tighten

    1. Tighten the lower intake manifold bolts in sequence to 7 N·m (62 lb in) on the first pass.
    2. Tighten the lower intake manifold bolts (1,2,3,4) in sequence to 13 N·m (115 lb in) on the final pass.
    3. Tighten the lower intake manifold bolts (5,6,7,8) in sequence to 25 N·m (18 lb ft) on the final pass.

    Object Number: 190522 Size: SH
  11. Install the thermostat bypass hose to the thermostat bypass pipe and lower intake manifold pipe.

    12. Object Number: 523326 Size: SH
  12. Install the heater inlet pipe.
  13. Install the heater inlet pipe nut.

    14. Tighten
    Tighten the heater inlet pipe nut to 25 N·m (18 lb ft).

  14. Install the radiator inlet hose to the engine. Refer to Radiator Inlet Hose Replacement in Engine Cooling.
  15. Install the power steering pump to the front engine cover. Refer to Power Steering Pump Replacement in Power Steering System.

    16. Object Number: 862487 Size: SH

    Important: Do not press on the fuel pressure regulator valve when installing the fuel injector rail assembly.

  16. Install the fuel injector rail assembly.
    17. 16.1. Install the fuel injector O-rings using GM P/N 12345616 (Canadian P/N 993182) or equivalent.
    16.2. Install the injector nozzles into the lower intake manifold injector bores.
    16.3. Press on the injector rail using the palms of both hands until the injectors are fully seated.
  17. Install the fuel injector rail bolts.

    18. Tighten
    Tighten the fuel injector rail bolts to 10 N·m (89 lb in).


    Object Number: 190513 Size: SH
  18. Install the fuel return pipe to the fuel injector rail. Refer to Fuel Hose/Pipes Replacement - Filter to Engine in Engine Controls - 3.1L.

    19. Object Number: 190514 Size: SH
  19. Install the fuel feed pipe to the fuel injector rail. Refer to Fuel Hose/Pipes Replacement - Filter to Engine in Engine Controls - 3.1L.

    20. Object Number: 187065 Size: SH
  20. Install the fuel feed and return pipe retaining clip.
  21. Install the fuel feed and return pipe retaining clip bolt.

    22. Tighten
    Tighten the fuel feed and return pipe retaining clip bolt to 8 N·m (71 lb in).


    Object Number: 190518 Size: SH
  22. Install and connect the fuel injector and the MAP sensor wiring harnesses.

    23. Object Number: 190517 Size: SH
  23. Connect the ECT sensor electrical connector.
  24. Install the right valve rocker arm cover. Refer to Valve Rocker Arm Cover Replacement - Right Side .
  25. Install the left valve rocker arm cover. Refer to Valve Rocker Arm Cover Replacement - Left Side .
  26. Install the upper intake manifold. Refer to Upper Intake Manifold Replacement .
  27. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  28. Inspect for leaks.