S&T Series Blazer, Bravada, Envoy, Jimmy, Rainier, Trailblazer, Xtreme

Intake Manifold

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Removal & Installation



4.2L Engine
  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Properly relieve the fuel system pressure.
  4.  
  5. Disconnect the negative battery cable.
  6.  
  7. Drain the engine cooling system.
  8.  
  9. Remove or disconnect the following:

    Throttle body
     
    Powertrain Control Module (PCM)
     
    All electrical harnesses from the engine harness bracket
     
    Front differential vent hose from the bracket clip
     
    Engine harness bracket bolt and bracket
     
    Manifold Absolute Pressure (MAP) sensor connector
     
    Crankcase ventilation hose
     
    Brake hose from the booster
     
    Alternator
     
    Intake manifold bolts and manifold.
     
    Manifold gasket
     

  10.  

To install:

  1. Clean the gasket mounting surfaces. Be sure to inspect the manifold for warpage and/or cracks. If necessary, replace it.
  2.  
  3. Properly position a new intake manifold gasket.
  4.  
  5. Install or connect the following:

    Intake manifold and bolts. Torque the bolts to 16 ft. lbs. (22 Nm).
     
    Alternator
     
    Brake hose to the booster
     
    Crankcase ventilation hose, lubricating the inner diameter first with 12345884, or equivalent lubricant
     
    MAP sensor electrical connector
     
    Engine harness bracket. Tighten the retaining bolt to 37 ft. lbs. (50 Nm).
     
    Front differential vent hose to the engine harness bracket clip
     
    All harnesses to their original locations onto the engine harness bracket
     
    PCM
     
    Throttle body
     
    Negative battery cable
     

  6.  
  7. Refill the engine cooling system.
  8.  

4.3L Engine

NOTE
If only the upper intake manifold is being removed, the fuel system pressure does not need to be released. ALWAYS release the pressure before disconnecting any fuel lines.

  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Remove the engine cover, if equipped
  4.  
  5. Properly relieve the fuel system pressure.
  6.  
  7. Disconnect the negative battery cable.
  8.  
  9. Drain the engine cooling system.
  10.  
  11. Remove or disconnect the following:

    Air cleaner and air inlet duct
     
    Wiring harness connectors and brackets
     
    Throttle linkage from the upper intake manifold
     
    Ignition coil
     
    Fuel lines and bracket from the rear of the lower intake manifold
     
    Brake booster vacuum hose at the upper intake manifold
     
    Positive Crankcase Ventilation (PCV) hose at the rear of the upper intake manifold
     
    Vacuum hoses from both the front and rear of the upper intake
     
    Purge solenoid and bracket
     
    Upper intake manifold
     
    Distributor or High Voltage Switch (HVS) assembly
     
    Upper radiator hose at the thermostat housing
     
    Heater hose at the lower intake manifold
     
    Wiring harnesses and brackets
     
    Automatic transmission dipstick tube
     
    Exhaust Gas Recirculation (EGR) tube, clamp and tube
     
    Air conditioning compressor bracket-to-lower intake manifold pencil brace
     
    Alternator bracket bolts near the thermostat housing
     
    Lower intake manifold
     

  12.  
  13. Insert clean rags into the openings in the cylinder head to prevent dirt and debris from entering the engine.
  14.  
  15. Clean the gasket mounting surfaces. Be sure to inspect the manifold for warpage and/or cracks. If necessary, replace it.

    Click image to see an enlarged view

    Fig. Intake manifold and related components

  16.  

To install:

  1. Remove the rags from the cylinder heads.
  2.  
  3. Position the gaskets on the cylinder head with the port blocking plates to the rear and the This Side Up stamps facing upward. Then apply a 3 / 16 in. (5mm) bead of RTV sealant on the front and rear of the engine block at the block-to-manifold mating surface. Extend the bead 1 / 2 in. (13mm) up each cylinder head to seal and retain the gaskets.
  4.  
  5. Install the lower intake manifold. Tighten the bolts in sequence and in 3 steps, as follows:


    1. Step 1: 26 inch lbs. (3 Nm).
    2.  
    3. Step 2: 106 inch lbs. (12 Nm).
    4.  
    5. Step 3: 11 ft. lbs. (15 Nm).

      Click image to see an enlarged view

      Fig. Intake manifold bolt tightening sequence-4.3L engine

    6.  

  6.  
  7. Install or connect the following:

    Alternator bracket bolt near the thermostat housing
     
    EGR tube, clamp and bolt
     
    Wiring harness to the lower manifold components, including the injector, EGR valve and ECT sensor
     
    Air conditioning compressor bracket-to-the lower intake manifold pencil braces
     
    Transmission oil dipstick tube, if necessary
     
    Fuel supply and return lines to the rear of the lower intake
     

  8.  
  9. Temporarily reattach the negative battery cable, then pressurize the fuel system (by cycling the ignition without starting the engine) and check for leaks.
  10.  
  11. Disconnect the negative battery cable.
  12.  
  13. Install or connect the following:

    Heater hose to the lower intake
     
    Upper radiator hose to the thermostat housing
     
    Distributor assembly and engage the wiring
     
    Vacuum hoses to the upper and lower intake manifold
     
    New upper intake manifold gasket, making sure the green sealing lines are facing upward
     
    Upper intake manifold being careful not to pinch the fuel injector wires between the manifolds
     
    Manifold retainers. Tighten them to 88 inch lbs. (10 Nm) using two passes.
     
    Purge solenoid and bracket
     
    Brake booster vacuum hose at the upper intake manifold
     
    PCV hose to the rear of the upper intake manifold
     
    Vacuum hoses to both the front and rear of the manifold assembly
     
    Throttle linkage to the upper intake
     
    Ignition coil
     
    Wiring to the upper intake components including the TP sensor, IAC motor, MAP sensor and the IMTV
     
    Plastic cover
     
    Air cleaner and air inlet duct
     
    Negative battery cable
     

  14.  
  15. Refill the engine cooling system.
  16.  

5.3L Engine

NOTE
The intake manifold, throttle body, fuel rail and injectors can be removed as an assembly. If you are not servicing these components individually, remove the intake manifold as a complete assembly.

  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Properly relieve the fuel system pressure.
  4.  
  5. Disconnect the negative battery cable.
  6.  
  7. Drain the engine cooling system.
  8.  
  9. Remove or disconnect the following:

    Air cleaner outlet duct
     
    A/C compressor pressure switch electrical connector
     
    Harness clip from the cylinder head and fuel raid
     
    Mass Airflow/Intake Air Temperature sensor connector
     

  10.  
  11. Disconnect the electrical connectors from the following:
    1. Main coil
    2.  
    3. Electronic Throttle Control (ETC)
    4.  
    5. Fuel injectors. Matchmark the connectors, pull the Connector Position Assurance (CPA) retainer up 1 click. Push the tab on the connector in, then detach the injector connector.

      Alternator connector
       
      Evaporative emission (EVAP) purge solenoid electrical connector
       
      Knock Sensor (KS) electrical connector
       
      Main coil
       
      Fuel injector electrical connector
       
      Electrical harness clips from the fuel rail
       
      KS harness electrical connector from the intake manifold
       
      Positive Crankcase Ventilation (PCV) valve hose and valve
       
      Heater water shutoff valve actuator inlet hose from the intake manifold
       
      EVAP purge solenoid vent tube
       
      Vacuum brake booster hose from the rear of the intake manifold
       
      Upper engine wire harness retainer nut. Position the wire harness aside.
       
      Intake manifold bolts
       
      Intake manifold and gaskets. Discard the gaskets.
       

    6.  

  12.  

To install:

  1. Clean the gasket mounting surfaces. Be sure to inspect the manifold for warpage and/or cracks. If necessary, replace it.
  2.  
  3. Properly position a new intake manifold gasket.

    Click image to see an enlarged view

    Fig. Make sure to use NEW intake manifold gaskets (1)-5.3L engine



    Click image to see an enlarged view

    Fig. Exploded view of the intake manifold-5.3L engine

  4.  
  5. Apply a 0.20 in. (5mm) band of a suitable threadlocking material to the intake manifold bolt threads.
  6.  
  7. Install or connect the following:

    Intake manifold and bolts. Torque the bolts, in sequence to 44 inch lbs. (5 Nm), then to 89 inch lbs. (10 Nm).

    Click image to see an enlarged view

    Fig. Intake manifold bolt tightening sequence-5.3L engine

     
    Route the electrical harness into position over the engine.
     
    Engine harness bracket nut and tighten to 89 inch lbs. (10 Nm)
     
    Vacuum brake booster hose to the rear of the intake manifold
     
    EVAP purge solenoid valve
     
    Heater water shutoff valve actuator inlet hose to the intake manifold
     
    PCV valve and hose
     
    EVAP purge solenoid, KS, MAP sensor, main coil & fuel injector electrical connectors
     
    Harness clips to the fuel rail
     
    Alternator electrical connector
     
    Main coil, ETC, fuel injector electrical connectors
     
    Electrical harness clips to the fuel rail
     
    A/C compressor pressure switch electrical connector
     
    Harness clip to the cylinder head
     
    Mass Airflow/Intake Air Temperature sensor connector
     
    Air cleaner outlet duct
     
    Fuel fill cap
     
    Negative battery cable
     

  8.  
  9. Refill the engine cooling system.
  10.  

 
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