Astro, Safari 1997-2005

Cylinder Head

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Removal & Installation



Left Side
  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. Properly discharge the air conditioning system, if equipped.
  8.  
  9. Remove or disconnect the following:
    NOTE
    The power steering pump can stay mounted on the bracket and the hoses should not be disconnected from the pump.


    NOTE
    If valve train components, such as the rocker arms or pushrods, are to be reused, they must be tagged or arranged to insure installation in their original locations.



    Negative battery cable
     
    Engine cover
     
    Engine cooling fan
     
    Accessory drive belt
     
    Air conditioning compressor, if equipped
     



    Nut holding the power steering pump rear bracket to the engine
     
    Power steering pump mounting bracket stud from the cylinder head.
     
    Intake manifold
     
    Exhaust manifold
     
    Ground wires at the rear of the left cylinder head
     
    A/C pipe bracket nut, if equipped
     
    Fuel pipe bracket bolt from the rear of the cylinder head
     
    Engine coolant temperature sensor
     
    Spark plugs
     
    Spark plug wire support
     
    Valve cover
     
    Pushrods by loosening the rocker arms
     

  10.  
  11. Remove cylinder head bolts by loosening them in the reverse of the torque sequence.
  12.  
  13. Remove cylinder head.
  14.  

To install:

  1. Clean and inspect the gasket mounting surfaces.
    NOTE
    Do not apply sealer to composition steel/asbestos gaskets. If using a steel only gasket, apply a thin and even coat of sealer to both sides of the gaskets.

  2.  
  3. Install new gasket over the dowel pins with the bead or the words This Side Up facing upwards, as applicable.
  4.  
  5. Install the cylinder head.
  6.  
  7. Coat the bolts with GM sealer 12346004 , then install the bolts and tighten in sequence to 22 ft. lbs. (30 Nm). The bolts must then be tightened again in sequence in the following order:
    1. Short length bolts: (11, 7, 3, 2, 6, 10) 55 degrees.
    2.  
    3. Medium length bolts: (12, 13) 65 degrees.
    4.  
    5. Long length bolts: (1, 4, 8, 5, 9) 75 degrees.
    6.  

  8.  
  9. Install pushrods, secure the rocker arms and adjust the valves.
  10.  
  11. Install or connect the following:

    Valve cover
     
    Spark plug wire support
     
    Spark plugs
     
    Engine coolant temperature sensor
     
    Ground wires and bolt at the rear of the head. Tighten the bolt to 26 ft. lbs. (35 Nm).
     
    Fuel pipe bracket and stud. Tighten the stud to 24 ft. lbs. (35 Nm).
     
    A/C pipe bracket and nut, and tighten to 26 ft. lbs. (35 Nm).
     
    Exhaust manifold
     
    Intake manifold
     
    Power steering pump mounting bracket stud. Tighten to 15 ft. lbs. (20 Nm).
     
    Power steering pump mounting bracket. Tighten the nut to 30 ft. lbs. (41 Nm).
     
    Air conditioning compressor, if equipped.
     
    Accessory drive belt
     
    Engine cooling fan
     
    Engine cover
     
    Negative battery cable
     

  12.  
  13. Refill the engine cooling system.
  14.  
  15. Start the engine to check for leaks.
  16.  
  17. Check and/or adjust the ignition timing.
  18.  

Right Side
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Properly relieve the fuel system pressure.
  4.  
  5. Drain the cooling system.
  6.  
  7. Remove or disconnect the following:
    NOTE
    If valve train components, such as the rocker arms or pushrods, are to be reused, they must be tagged or arranged to insure installation in their original locations.



    Negative battery cable
     
    Engine cover
     
    Engine cooling fan
     
    Air intake assembly
     
    PCV hose from valve cover
     
    Valve cover
     
    Intake manifold
     
    Spark plugs
     
    Spark plug wire support
     
    Exhaust manifold
     
    Alternator mounting bracket
     
    Alternator mounting bracket stud from cylinder head
     
    Engine wiring harness bolt/clip at the rear of the cylinder head
     
    Rocker arms
     
    Pushrods
     

  8.  
  9. Remove cylinder head bolts by loosening them in the reverse of the torque sequence.
  10.  
  11. Remove cylinder head.

    Click image to see an enlarged view

    Fig. Cylinder head and related components-4.3L engine

  12.  

To install:

  1. Clean and inspect the gasket mounting surfaces.
    NOTE
    Do not apply sealer to composition steel/asbestos gaskets. If using a steel only gasket, apply a thin and even coat of sealer to both sides of the gaskets.

  2.  
  3. Install new gasket over the dowel pins with the bead or the words This Side Up facing upwards, as applicable.
  4.  
  5. Install cylinder head.

    Click image to see an enlarged view

    Fig. Cylinder head bolt torque sequence-4.3L engine

  6.  
  7. Using new bolts, coat the bolts with GM sealer 12346004 , then install the bolts and tighten in sequence to 22 ft. lbs. (30 Nm). The bolts must then be tightened again in sequence in the following order:
    1. Short length bolts: (11, 7, 3, 2, 6, 10) 55 degrees.
    2.  
    3. Medium length bolts: (12, 13) 65 degrees.
    4.  
    5. Long length bolts: (1, 4, 8, 5, 9) 75 degrees.
    6.  

  8.  
  9. Install or connect the following:

    Pushrods
     
    Rocker arms
     
    Exhaust manifold
     
    Spark plug wire harness and support. Tighten the bolts to 106 inch lbs. (12 Nm).
     
    Intake manifold
     
    Alternator mounting bracket stud and tighten to 15 ft. lbs. (20 Nm)
     
    Alternator mounting bracket
     
    Engine wiring harness to the rear of the head. Tighten mounting bolt to 27 ft. lbs. (36 Nm).
     
    Valve cover
     
    PCV hose
     
    Air intake assembly
     
    Engine cooling fan
     
    Engine cover
     
    Negative battery cable
     

  10.  
  11. Refill the engine cooling system.
  12.  
  13. Start the engine to check for leaks
  14.  
  15. Check and/or adjust the ignition timing.
  16.  

 
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