Montana, Silhouette, Venture 2000-2005

Intake Manifold

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Removal & Installation



3.5L Engine
Lower Manifold

CAUTION
This engine uses a sequential multiport fuel injection system. Injector wiring harness connectors must be connected to the appropriate fuel injector.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Drain the cooling system.
  4.  
  5. Remove or disconnect the following:

    Upper intake manifold; see Upper Manifold
     
    Both rocker arm covers; see Rocker Arms/Covers
     
    Engine coolant temperature (ECT) wiring harness
     
    Fuel injector and manifold air pressure (MAP) wiring harness
     

  6.  
  7. Remove the fuel injector rail after removing 2 retaining bolts.
  8.  
  9. Remove the heater inlet pipe, with heater hose, from the lower intake manifold and reposition aside.
  10.  
  11. Remove the radiator inlet hose from the engine.
  12.  
  13. Remove or disconnect the following:
    CAUTION
    Keep components separated in order to reinstall in the same location.



    Water outlet
     
    Thermostat
     
    Lower intake manifold bolts
     
    Lower intake manifold
     
    Valve rocker arms and pushrods
     



    Lower intake manifold gaskets and seals

    Click image to see an enlarged view

    Fig. Removing/installing the fuel rail assembly



    Click image to see an enlarged view

    Fig. Removing lower intake manifold and gaskets

     

  14.  

To install:

  1. Install or connect the following:
    NOTE
    The intake pushrods are identified with yellow stripes and are 3-5 / 4 inches long. Exhaust pushrods are identified with green stripes and are 6 inches long.


    NOTE
    With gaskets and seals in place apply a small drop of RTV sealer or equivalent, to the 4 corners of the intake manifold to block joints (1).


    NOTE
    Maximum gasket performance is achieved when using new fasteners that contain a thread locking patch. If the fasteners are not replaced, a thread locking chemical must be applied to the fastener threads. Failure to replace the fasteners or apply a thread-locking chemical MAY reduce gasket sealing capability.


    CAUTION
    Failure to tighten vertical bolts before the diagonal bolts may cause an oil leak



    Lower intake manifold gaskets
     
    Valve rocker arms and pushrods
     



    Lower intake manifold
     



    Click image to see an enlarged view

    Fig. Lower intake manifold torque sequence-3.5L and 3.9L engines

  2.  
  3. Install and tighten the new lower intake manifold bolts in sequence as follows:
    1. Tighten the lower intake manifold bolts in sequence to 115 inch lbs. (13 Nm) on the first pass.
    2.  
    3. Tighten the lower intake manifold bolts (1, 2, 3, and 4) in sequence to 15 ft. lbs. (20 Nm) on the final pass.
    4.  
    5. Tighten the lower intake manifold bolts (5, 6, 7, and 8) in sequence to 18 ft. lbs. (25 Nm) on the final pass.
    6.  

  4.  
  5. Install the heater inlet pipe and nut; tighten the heater inlet pipe nut to 18 ft. lbs. (25 Nm).
  6.  
  7. Install or connect the following:

    Thermostat
     
    Water outlet bolts
     
    ECT sensor, tighten the ECT sensor to 15 ft. lbs. (20 Nm)
     
    Thermostat bypass hose to the thermostat bypass pipe and lower intake manifold pipe
     
    Radiator inlet hose to the engine
     
    Heater inlet pipe and heater hose to the lower intake manifold
     
    Fuel injector rail
     
    Fuel injector and MAP wiring harness
     
    ECT wiring harness
     
    Rocker arm covers; see Rocker Arms/Covers.
     
    Upper intake manifold; see Upper Manifold.
     
    Negative battery cable
     

  8.  
  9. Refill the cooling system.
  10.  
  11. Start and run the engine to check for leaks.
  12.  

Upper Manifold
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Drain the cooling system
  4.  
  5. Remove or disconnect the following:

    Negative battery cable
     
    Vacuum hose to EVAP canister purge valve
     
    Vacuum hose to brake booster
     
    EGR electrical connector
     
    Mass air flow sensor electrical connector
     
    Throttle control valve electrical connector
     
    EVAP canister purge valve electrical connector
     
    Air cleaner intake duct
     
    Left side spark plug wires
     
    Camshaft position sensor (CMP) wiring harness from retainer
     
    Left side spark plug wire harness from retainer
     
    Engine wiring harness from retainer
     
    Ignition coil bracket and coils
     
    EVAP canister purge solenoid valve
     
    Manifold absolute pressure (MAP) sensor and bracket
     

  6.  
  7. Remove the EGR valve as follows:
    1. Disconnect the electrical connector (1) from the exhaust gas recirculation (EGR) valve (2), as shown.
    2.  
    3. Raise and safely support the vehicle.
    4.  
    5. Remove the transaxle filler tube retaining fasteners to the transaxle case and position the filler tube out-of-the-way.
    6.  
    7. Lower the vehicle.
    8.  
    9. Remove the EGR pipe bolt and carefully pull the pipe assembly back.
    10.  
    11. Remove the EGR valve bolts.
    12.  
    13. Remove EGR valve.
    14.  
    15. Remove the EGR valve gasket.
    16.  
    17. Clean and inspect the EGR valve gasket mating surfaces.
    18.  

  8.  
  9. Remove the upper intake manifold bolts and the stud.
  10.  
  11. Remove the alternator bracket after removing the alternator and drive belt tensioner.
  12.  
  13. Remove the upper intake manifold and gasket.
  14.  
  15. If replacing the upper intake manifold, transfer the throttle body.

    Click image to see an enlarged view

    Fig. Detaching EGR Valve electrical connector



    Click image to see an enlarged view

    Fig. Removing the EGR Valve

  16.  
  17. If necessary to transfer the throttle body, remove it as follows:
    1. Disconnect the electronic throttle control (ETC) electrical connector (1) from the throttle body (2).

      Click image to see an enlarged view

      Fig. Disconnect ETC connector (1) from the throttle body (2)

    2.  
    3. Remove the heater pipe nut at the throttle body.
    4.  
    5. Remove only the heater inlet pipe.

      Click image to see an enlarged view

      Fig. Remove the heater inlet pipe (1) only

    6.  
    7. Remove the nuts and the bolts from the throttle body.
    8.  
    9. Remove the throttle body assembly.
    10.  
    11. Remove the throttle body gasket.
      CAUTION
      Do not use solvent of any type when cleaning the gasket surfaces on the intake manifold and the throttle body assembly, as damage to the gasket surfaces and throttle body assembly may result. Use care in cleaning the gasket surfaces on the intake manifold and the throttle body assembly, as sharp tools may damage the gasket surfaces.

    12.  
    13. Clean and inspect the throttle body gasket mating surfaces.
    14.  

  18.  

To install:

  1. If removed, install the throttle body to the upper intake manifold, as follows:
    1. Install a new gasket, if necessary.
    2.  
    3. Install the throttle body assembly.
    4.  
    5. Install the throttle body nuts and the bolts. Tighten the nuts and the bolts to 89 inch lbs. (10 Nm).
    6.  
    7. Install the heater inlet pipe.
    8.  
    9. Install the heater pipe nut to the throttle body. Tighten the nut to 18 ft. lbs. (25 Nm).
    10.  
    11. Connect the ETC electrical connector (1) to the throttle body (2).
    12.  

  2.  
  3. Install or connect the following:

    Intake manifold with new gasket
     
    Apply threadlock (GM P/N 12345382, or equivalent) to the intake manifold bolts
     
    Upper intake manifold bolts and the stud; tighten the bolts to 18 ft. lbs. (25 Nm)
     
    Generator bracket. Torque bracket bolts to 37 ft. lbs. (50 Nm).
     

  4.  
  5. Install the EGR valve as follows:
    1. Install a new EGR valve gasket.
    2.  
    3. Install the EGR valve.
    4.  
    5. Install the EGR valve bolts. Tighten the bolt to 22 ft. lbs. (30 Nm).
    6.  
    7. Install the EGR pipe to the EGR valve.
    8.  
    9. Install the EGR pipe. Tighten the bolt to 18 ft. lbs. (25 Nm).
    10.  
    11. Connect the electrical connector (1) to the EGR valve (2).
    12.  
    13. Raise and safely support the vehicle.
    14.  
    15. Position the transaxle filler tube to the normal installed position and install the filler tube to transaxle case fasteners. Tighten the fasteners to 115 ft. lbs. (130 Nm).
    16.  
    17. Lower the vehicle.
    18.  

  6.  
  7. Install or connect the following:

    MAP sensor bracket and sensor; tighten retaining bolt to 89 inch lbs. (10 Nm)
     
    EVAP canister purge solenoid valve; tighten bracket bolt to 89 inch lbs. (10 Nm)
     
    Ignition coil bracket and coils; tighten bolts to 40 inch lbs. (4.5 Nm)
     
    Camshaft position sensor (CMP) wiring harness to retainer
     
    Left side spark plug wire harness to retainer
     
    Engine wiring harness to retainer
     
    Left side spark plug wires
     
    Air cleaner intake duct
     
    EGR electrical connector
     
    Mass air flow sensor electrical connector
     
    Throttle control valve electrical connector
     
    EVAP canister purge valve electrical connector
     
    Vacuum hose to EVAP canister purge valve
     
    Vacuum hose to brake booster
     
    Negative battery cable
     

  8.  
  9. Fill the cooling system.
  10.  
  11. Start the engine and check for leaks.
  12.  

3.9L Engine
Lower Manifold
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Drain the cooling system,
  6.  
  7. Remove the coolant crossover pipe as follows:
    1. Remove the intake manifold cover.
    2.  
    3. Remove the alternator.
    4.  
    5. Remove the accessory drive belt and idler pulleys.
    6.  
    7. Remove the power steering pump.
    8.  
    9. Remove the coolant recovery reservoir inlet hose from the coolant crossover.
    10.  
    11. Remove the radiator inlet hose from the crossover pipe.
    12.  
    13. Remove the thermal bypass hose from the crossover pipe.
    14.  
    15. Remove the bolts holding the heater pipe and wiring harness at the coolant crossover pipe and position the heater pipe aside.
    16.  
    17. Remove the crossover pipe mounting bolts and remove the crossover pipe.

      Click image to see an enlarged view

      Fig. Remove the crossover pipe mounting bolts (1-4) to remove the crossover pipe-3.9L engine

    18.  

  8.  
  9. Remove the upper intake manifold. For additional information, please refer to following section, -Intake manifold, Removal & Installation, Upper Manifold.-
  10.  
  11. Remove the valve covers.
  12.  
  13. Disconnect the engine coolant temperature sensor electrical connector.
  14.  
  15. Remove the fuel rail. For additional information, please refer to following section, -Fuel Rail, Removal & Installation.-
  16.  
  17. Remove the lower intake manifold mounting bolts.
  18.  
  19. Remove the lower intake manifold.
  20.  
  21. Remove the lower intake manifold gaskets and seals.
  22.  

To install:

  1. Clean the gasket and seal surfaces on the cylinder head, engine block and lower intake manifold.
  2.  
  3. Remove all loose RTV from the sealing surfaces.
  4.  
  5. Install new lower intake manifold gaskets and seals.
    CAUTION
    RTV sealer is not be placed under the lower intake manifold gaskets.

  6.  
  7. Apply a small drop of RTV sealer to he four corners of the intake manifold-to-engine block joints.

    Click image to see an enlarged view

    Fig. Apply a small drop of RTV to the corners where the intake manifold meets the engine block-3.9L engine

  8.  
  9. Install the lower intake manifold and tighten the bolts as follows:
    1. Tighten bolts 1-4 in sequence to 12 ft. lbs. (16 Nm).
    2.  
    3. Tighten bolts 5-8 in sequence to 18 ft. lbs. (25 Nm).
    4.  

  10.  
  11. Install the fuel rail.
  12.  
  13. Install the valve covers.
  14.  
  15. Install the upper intake manifold.
  16.  
  17. Install the coolant crossover pipe and tighten the mounting bolts to 37 ft. lbs. (50 Nm).
  18.  
  19. The remainder of the installation is the reverse order of removal.
  20.  
  21. Refill the cooling system to the correct level.
  22.  
  23. Start the engine and check for leaks.
  24.  

Upper Manifold
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Drain the cooling system.
  6.  
  7. Remove the intake manifold cover.
  8.  
  9. Remove the positive crankcase ventilation (PCV) fresh air tube and foul air tube.
  10.  
  11. Reposition the brake booster vacuum hose clamp at the intake manifold.
  12.  
  13. Remove the vacuum hose from the intake manifold.
  14.  
  15. Disconnect the engine wiring harness from the following electrical connectors:

    Manifold absolute pressure (MAP) sensor
     
    Evaporative emission (EVAP) canister purge solenoid
     
    Electronic throttle control (ETC)
     
    Intake manifold tuning valve
     

  16.  
  17. Remove the air intake assembly.
  18.  
  19. Remove the left side spark plug wires.
  20.  
  21. Remove the heater pipe mounting nuts from the manifold.
  22.  
  23. Remove the alternator bracket from the manifold.
  24.  
  25. Remove the transmission dipstick tube mounting bolt in the manifold.
  26.  
  27. Remove the ignition coils.
  28.  
  29. Remove the upper intake manifold mounting bolts.

    Click image to see an enlarged view

    Fig. Remove the upper intake manifold bolts (1, 2) and stud (3) to remove-3.9L Engine

  30.  
  31. Separate and remove the upper intake manifold from the lower intake manifold.
  32.  
  33. Remove the gaskets.
  34.  

To install:

  1. Install new upper-to-lower intake manifold gaskets.
  2.  
  3. Apply threadlocker to the upper intake manifold bolts/stud threads.
  4.  
  5. Install the upper intake manifold and tighten the bolts /nuts to 18 ft. lbs. (25 Nm).
  6.  
  7. install the ignition coils.
  8.  
  9. Reposition the transmission dipstick tube and install the mounting bolt.
  10.  
  11. Install the alternator bracket to the manifold.
  12.  
  13. Reattach the heater pipes to the mounts on the intake manifold and tighten the nuts to 89 inch lbs. (10 Nm).
  14.  
  15. Install the left side spark plug wires.
  16.  
  17. Install the air intake assembly.
  18.  
  19. Connect the wiring harness to the following electrical connectors:

    Intake manifold tuning valve
     
    ETC
     
    EVAP purge solenoid
     
    MAP sensor
     

  20.  
  21. Install the PCV foul air and fresh air tube.
  22.  
  23. Install the intake manifold cover.
  24.  
  25. Refill the cooling system to the correct level.
  26.  
  27. Connect the negative battery cable.
  28.  
  29. Start the engine and check for leaks.
  30.  

Lower Manifold

This engine uses a 2-piece intake manifold. The upper half (often called a plenum) mounts the throttle body. The lower half of the manifold bolts to the engine and contains the fuel injectors. Please note that this engine uses a sequential multi-port fuel injection system. Injector connectors must be connected to their appropriate fuel injector assembly or engine emissions and engine performance will be seriously affected. Identify and tag for identification all wiring connectors as well as vacuum and other components as required to assure correct assembly.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Drain the engine coolant.
  4.  
  5. Relieve the fuel system pressure using the recommended procedure.
  6.  
  7. Remove or disconnect the following:
    NOTE
    Do not disconnect the power steering pipes or hoses from the steering pump.



    Negative battery cable
     
    Upper intake manifold
     
    Left side valve rocker arm cover
     
    Right side valve rocker arm cover
     
    Wire harness from the Engine Coolant Temperature (ECT) sensor
     
    Fuel injector, Manifold Absolute Pressure (MAP) and ECT wire harness
     
    Fuel feed and return pipe from the injector rail

    Click image to see an enlarged view

    Fig. Remove the fuel injector rail

     



    Fuel injector rail
     
    Power steering pump from the front cover
     



    Heater inlet pipe with the heater hose from the lower intake manifold
     
    Radiator inlet hose
     
    Thermostat bypass hose from the manifold
     
    Lower intake manifold

    Click image to see an enlarged view

    Fig. Lower intake manifold assembly



    Click image to see an enlarged view

    Fig. Lower intake manifold assembly torque sequence

     



    Pushrods after loosening the rocker arms
     
    Lower intake manifold gasket and seals
     
    ECT sensor, if replacing the manifold
     
    Thermostat and housing, if replacing the manifold
     

  8.  

To install:

  1. Clean the gasket mounting surfaces.
  2.  
  3. Inspect the intake manifold for cracks or damage, replace if necessary.
  4.  
  5. Install or connect the following:

    ECT sensor, if removed. Torque the sensor to 17 ft. lbs. (23 Nm).
     
    Thermostat and housing, if removed. Torque the fastener to 18 ft. lbs. (25 Nm).
     
    Thin bead of RTV sealer (such as GM 12345739) on the ridge of the engine block where the lower intake manifold makes contact
     
    Lower intake manifold gaskets
     
    Pushrods and tighten the rocker arms. Torque the arms to 14 ft. lbs. (19 Nm) plus 30 degrees.
     
    Lower intake manifold. Torque the bolts to first to 62 inch lbs. (7 Nm) then to 115 inch lbs. (13 Nm) after applying a sealant (such as GM 12345382) to the threads of the bolts.
     
    Thermostat bypass hose to the lower intake manifold pipe. Torque the fastener to 18 ft. lbs. (25 Nm).
     
    Radiator inlet hose from the engine
     
    Power steering pump to the front cover
     
    Fuel injector rail. Torque the fastener to 89 inch lbs. (10 Nm).
     
    Fuel feed and return pipes to the injector rail. Torque the fasteners to 13 ft. lbs. (17 Nm).
     
    Wire harness for the fuel injector, MAP sensor and the ECT sensor
     
    Right side rocker arm cover. Torque the bolts to 89 inch lbs. (10 Nm).
     
    Left side rocker arm cover. Torque the bolts to 89 inch lbs. (10 Nm).
     
    Upper intake manifold. Torque the bolts to 18 ft. lbs. (25 Nm).
     
    Negative battery cable
     

  6.  
  7. Fill the coolant system.
  8.  
  9. Turn the ignition to the ON position several times to pressurize the fuel system.
  10.  
  11. Start the engine and check for any leakage and repair if necessary.
  12.  
  13. Check and top off all fluid levels if needed.
  14.  

 
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