Astro, Safari 1997-2005

Intake Manifold

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Removal & Installation




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. Properly relieve the fuel system pressure.
  4.  
  5. Drain the engine cooling system.
  6.  
  7. Remove or disconnect the following:

    Negative battery cable
     
    Engine cover
     
    Air intake assembly
     
    Throttle body
     
    Throttle linkage from the upper intake manifold
     
    Positive Crankcase Ventilation (PCV) hose at the rear of the upper intake manifold
     
    Engine wiring harness bracket
     
    A/C compressor clutch connector
     
    A/C high pressure cutoff switch connector
     
    Throttle position (TP) sensor
     
    Idle air control (IAC) motor connector
     
    Fuel meter body assembly connector
     
    Manifold absolute pressure (MAP) sensor
     
    EVAP canister purge solenoid valve
     
    Ground strap
     
    Vacuum hoses from both the front and rear of the upper intake
     
    Automatic transmission dipstick tube
     
    Brake booster vacuum hose at the upper intake manifold
     
    Upper intake manifold
     
    Lower manifold wiring harness
     
    Distributor or High Voltage Switch (HVS) assembly
     
    Fuel lines and bracket from the rear of the lower intake manifold
     
    Ignition coil
     
    Upper radiator hose at the thermostat housing
     
    Heater hose at the lower intake manifold
     
    Air conditioning compressor bracket-to-lower intake manifold pencil brace
     
    Alternator bracket bolts near the thermostat housing
     

  8.  
  9. Loosen the power steering pump rear bracket and slide the power steering pump forward.
  10.  
  11. Remove the lower intake manifold.

    Click image to see an enlarged view

    Fig. Intake manifold and related components-4.3L engine

  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. 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.

    Click image to see an enlarged view

    Fig. Lower intake manifold tightening sequence-4.3L engines

  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: 133 inch. lbs. (15 Nm).
    6.  

  6.  
  7. Install or connect the following:

    Power steering pump
     
    Alternator bracket bolt near the thermostat housing
     
    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
     

  8.  
  9. Install transmission oil dipstick tube, if necessary.

    Fuel supply and return lines to the rear of the lower intake
     

  10.  
  11. Temporarily reattach the negative battery cable, then pressurize the fuel system (by cycling the ignition without starting the engine) and check for leaks.
  12.  
  13. Disconnect the negative battery cable.
  14.  
  15. Install or connect the following:

    Heater hose to the lower intake
     
    Upper radiator hose to the thermostat housing
     
    Distributor assembly and engage the wiring
     
    Ignition coil
     
    Connect 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
     
    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 body
     
    Throttle linkage to the upper intake
     
    Wiring to the upper intake components including the TP sensor, IAC motor, MAP sensor and the fuel meter
     
    Engine cover
     
    Air intake assembly
     

  16.  
  17. Connect negative battery cable.
  18.  
  19. Refill the engine cooling system.
  20.  
  21. Start the engine and check for leaks.
  22.  

 
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