GM Full-Size Trucks 1988-1998 Repair Information

Cylinder Head

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REMOVAL & INSTALLATION




CAUTION
Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

4.8L Engines

See Figure 1

  1. Disconnect the negative battery cable and unbolt it at the engine.
  2.  
  3. Drain the cooling system.
  4.  
  5. Remove the air cleaner assembly.
  6.  
  7. Disconnect the fuel line at the carburetor.
  8.  
  9. Disconnect the accelerator and transmission linkages.
  10.  
  11. Mark and disconnect all required electrical and vacuum lines.
  12.  
  13. Remove the combination manifold assembly retaining bolts.
  14.  
  15. Remove the combination manifold from the engine.
  16.  
  17. Remove the cylinder head cover.
  18.  
  19. Remove the rocker arms and pushrods. Keep them in order for re-installation.
  20.  
  21. If equipped, disconnect the AIR injection hose at the check valve.
  22.  
  23. Disconnect the upper radiator hose at the thermostat housing.
  24.  
  25. Remove the cylinder head retaining bolts.
  26.  
  27. With the aid of an assistant, lift the cylinder head from the engine.
  28.  

To install:
  1. Thoroughly clean both the head and block surfaces.
  2.  
  3. Install a new head gasket on the block. If an all steel gasket is used, coat both sides with sealer. If a composition gasket is used, do not use sealer. Position the gasket on the block with the bead up.
  4.  



Click image to see an enlarged view

Fig. Fig. 1: Cylinder head bolt tightening sequence-4.8L engines

  1. With the aid of an assistant, lower the cylinder head onto the engine.
  2.  
  3. Coat the threads of the head bolts with sealer and install them. Tighten the bolts, in 3 equal steps, in the sequence shown, to 95 ft. lbs. (129 Nm) for all but the left front (No. 12) bolt. Tighten that one to 85 ft. lbs. (115 Nm).
  4.  
  5. Connect the upper radiator hose at the thermostat housing.
  6.  
  7. Connect the AIR injection hose at the check valve.
  8.  
  9. Install the rocker arms and pushrods. Adjust the valves.
  10.  
  11. Install the cylinder head cover.
  12.  
  13. Install the combination manifold.
  14.  
  15. Connect all electrical and vacuum lines.
  16.  
  17. Connect the accelerator and transmission linkages.
  18.  
  19. Connect the fuel line at the carburetor.
  20.  
  21. Install air cleaner assembly.
  22.  
  23. Fill the cooling system.
  24.  
  25. Install the negative battery cable.
  26.  

4.3L Engines

See Figure 2

  1. Disconnect the negative battery cable.
  2.  
  3. Drain the coolant.
  4.  
  5. Remove the intake manifold.
  6.  
  7. Remove the exhaust manifold.
  8.  
  9. If equipped, remove the air pipe at the rear of the right cylinder head.
  10.  
  11. On models equipped, remove the air pump mounting bolt and spacer at the right side cylinder.
  12.  
  13. On 1996-98 models, remove the alternator and bracket.
  14.  
  15. On 1988-95 models, remove the engine accessory bracket bolts and studs at the cylinder head. If you are removing the left cylinder head, it may be necessary to loosen the remaining bracket bolts to provide clearance for head removal.
  16.  
  17. On 1996-98 models, remove the power steering pump and brackets from the left cylinder head, and lay them aside.
  18.  
  19. On 1996-98 models, remove the air conditioner compressor, and lay it aside.
  20.  
  21. Remove the spark plug wires at their brackets, the ground strap from the right side and the coolant sensor wire from the left head.
  22.  
  23. Remove the cylinder cover.
  24.  
  25. Remove the spark plugs.
  26.  
  27. Remove the pushrods.
  28.  



Click image to see an enlarged view

Fig. Fig. 2: Cylinder head bolt tightening sequence-1988-98 4.3L engines

  1. Remove the cylinder head bolts in the reverse order of the tightening sequence.
  2.  
  3. Remove the cylinder head and gasket.
  4.  

To install:
  1. Clean all gasket mating surfaces, install a new gasket and reinstall the cylinder head. Install the cylinder heads using new gaskets.
  2.  

Coat a steel gasket on both sides with sealer. If a composition gasket is used, do not use sealer.

  1. Clean the cylinder head bolts, apply sealer to the threads, and install them hand-tight.
  2.  
  3. Tighten the head bolts a little at a time in the sequence shown. Tighten the bolts in three stages:
  4.  

1988-95 models:



First pass: 25 ft. lbs. (34 Nm)
 
Second pass: 45 ft. lbs. (61 Nm)
 
Final pass: 65 ft. lbs. (90 Nm)
 

On 1996-98 models install the bolts in sequence to 22 ft. lbs. (30 Nm). The bolts must then be tightened again in sequence in the following order:



Short length bolt: (11, 7, 3, 2, 6, 10) 55 degrees
 
Medium length bolt: (12, 13) 65 degrees
 
Long length bolts: (1, 4, 8, 5, 9) 75 degrees
 

  1. Install the pushrods.
  2.  
  3. Adjust the rocker arms.
  4.  
  5. Install the spark plugs.
  6.  
  7. Install the rocker arm cover.
  8.  
  9. If removed, install the air conditioner compressor.
  10.  
  11. If removed, install the power steering pump and brackets.
  12.  
  13. If removed, install the alternator and bracket.
  14.  
  15. On models equipped, install the air pump spacer and mounting bolt at the right side cylinder.
  16.  
  17. If equipped, install the air pipe at the rear of the head.
  18.  
  19. Install the exhaust manifold.
  20.  
  21. Install the intake manifold.
  22.  
  23. Fill the engine with coolant.
  24.  
  25. Connect the negative battery cable.
  26.  

5.0L and 5.7L Engines

See Figures 3, 4, 5, 6, 7 and 8

  1. Disconnect the negative battery cable and drain the coolant.
  2.  
  3. Remove the intake manifold.
  4.  
  5. Remove the exhaust manifolds and position them out of the way.
  6.  
  7. On 1988-95 models, if removing the right cylinder head, remove the following components.
    1. Remove the AIR pipe at the rear of the right cylinder head.
    2.  
    3. Remove the AIR pump bolt and spacer
    4.  
    5. Unfasten the nut and stud attaching to A/C compressor to the head and set the compressor aside with the hoses still attached.
    6.  
    7. Remove the fuel pipe, plug wire and wiring harness brackets at the rear of the cylinder head.
    8.  
    9. Remove the ground strap at the rear of the right side cylinder head.
    10.  

  8.  
  9. On 1996-98 models, if removing the right cylinder head, remove the following components.
    1. Remove the alternator and bracket.
    2.  
    3. Remove the ground strap at the rear of the right side cylinder head.
    4.  
    5. Remove the oil dipstick tube.
    6.  
    7. Remove the spark plug wire brackets from the rear of the head.
    8.  

  10.  
  11. On 1988-95 models, if removing the left cylinder head, remove the following components.
    1. Remove the nut and stud attaching the main accessory bracket to the head. It also may be necessary to loosen the remaining bolts and studs and move the bracket forward slightly for clearance to move the cylinder head.
    2.  
    3. Unplug the coolant sensor wire and remove the spark plug wire brackets at the rear of the head.
    4.  

  12.  
  13. On 1996-98 models, if removing the left cylinder head, remove the following components.
    1. Remove the A/C compressor and bracket and set the compressor aside with the hoses still attached.
    2.  
    3. Remove the EGR inlet tube.
    4.  
    5. Unplug the coolant sensor wire and remove the wiring harness brackets at the rear of the head.
    6.  

  14.  
  15. Remove the cylinder head covers. Remove the spark plugs.
  16.  
  17. Back off the rocker arm nuts and pivot the rocker arms out of the way so that the pushrods can be removed. Identify the pushrods so that they can be installed in their original positions.
  18.  
  19. Remove the cylinder head bolts in the reverse order of the tightening sequence and then remove the heads.
  20.  



Click image to see an enlarged view

Fig. Fig. 3: Using a breaker bar, remove the cylinder head bolts in the reverse order of the tightening sequence



Click image to see an enlarged view

Fig. Fig. 4: After removing all the cylinder head bolts, remove the cylinder head

To install:
  1. Inspect the cylinder head and block mating surfaces. Clean all old gasket material.
  2.  
  3. Install the cylinder heads using new gaskets. Install the gaskets with the word HEAD up.
  4.  

Coat a steel gasket on both sides with sealer. If a composition gasket is used, do not use sealer.

  1. Clean the bolts, apply sealer to the threads, and install them hand-tight.
  2.  

  1. Tighten the cylinder head bolts a little at a time, in the sequence shown. Tighten the bolts in three stages:

    First pass: 25 ft. lbs. (34 Nm)
     
    Second pass: 45 ft. lbs. (61 Nm)
     
    Final pass: 65 ft. lbs. (90 Nm)
     

  2.  

On 1996-98 models, install the bolts in sequence to 22 ft. lbs. (30 Nm). The bolts must then be tightened again in sequence in the following order:



Short length bolt: (3, 4, 7, 8, 11, 12, 15, 16) 55 degrees
 
Medium length bolt: (14, 17) 65 degrees
 
Long length bolts: (1, 2, 5, 6, 9, 10, 13) 75 degrees
 

  1. Install the pushrods so that they are in their original positions. Swing the rocker arms into position and tighten the bolts.
  2.  
  3. Install the cylinder head covers. Install the spark plugs.
  4.  
  5. On 1988-95 models, if installing the right cylinder head, install the following components.
    1. Install the AIR pipe at the rear of the right cylinder head.
    2.  
    3. Install the AIR pump bolt and spacer
    4.  
    5. Attach the A/C compressor to the head and tighten the retaining bolt and stud.
    6.  
    7. Install the fuel pipe, plug wire and wiring harness brackets at the rear of the cylinder head.
    8.  
    9. Remove the ground strap at the rear of the right side cylinder head.
    10.  

  6.  
  7. On 1996-98 models, if installing the right cylinder head, install the following components.
    1. Install the alternator and bracket.
    2.  
    3. Install the ground strap at the rear of the right side cylinder head.
    4.  
    5. Install the oil dipstick tube.
    6.  
    7. Install the spark plug wire brackets from the rear of the head.
    8.  

  8.  
  9. On 1988-95 models, if installing the left cylinder head, install the following components.
    1. Install the nut and stud attaching the main accessory bracket to the head. It loosened, tighten the remaining bolts and studs that were unfastened to allow clearance when removing the head.
    2.  
    3. Attach the coolant sensor wire and install the spark plug wire brackets at the rear of the head.
    4.  

  10.  
  11. On 1996-98 models, if installing the left cylinder head, install the following components.
    1. Install the A/C compressor and bracket.
    2.  
    3. Install the EGR inlet tube.
    4.  
    5. Attach the coolant sensor wire and install the wiring harness brackets at the rear of the head.
    6.  

  12.  
  13. If the right side cylinder head is being installed, install the AIR pump bolt and spacer, then install the nut and stud attaching to A/C compressor to the head.
  14.  
  15. If installing the left cylinder head, tighten the nut and stud attaching the main accessory bracket to the head. Tighten the remaining bolts and studs that were loosened for clearance. Attach the coolant sensor wire and install the spark plug wire brackets at the rear of the head.
  16.  
  17. Install the AIR pipe.
  18.  
  19. Install the ground strap at the rear of the right side cylinder head.
  20.  
  21. Install the exhaust manifold(s).
  22.  
  23. Install the intake manifold.
  24.  
  25. Fill the cooling system and connect the negative battery cable.
  26.  



Click image to see an enlarged view

Fig. Fig. 5: Remove and discard the old cylinder head gasket



Click image to see an enlarged view

Fig. Fig. 6: Using a scraper, remove the old gasket residue from both mating surfaces



Click image to see an enlarged view

Fig. Fig. 7: Cylinder head bolt tightening sequence-1988-98 5.0L and 5.7L engines



Click image to see an enlarged view

Fig. Fig. 8: Using a torque wrench, tighten the cylinder head bolts in sequence

6.2L and 6.5L Diesel Engines

See Figures 9 and 10

  1. Disconnect the negative battery cables. Drain the cooling system.
  2.  
  3. Remove the intake manifold.
  4.  
  5. Remove the fuel injection lines. Refer to Fuel Systems for this procedure.
  6.  
  7. Remove the cruise control transducer (if so equipped).
  8.  
  9. Remove the valve covers.
  10.  
  11. Drain the cooling system.
  12.  
  13. Raise the truck and support it with jack stands.
  14.  
  15. Remove the exhaust pipe from the exhaust manifold.
  16.  
  17. Lower the truck.
  18.  
  19. To remove the right cylinder head, remove the following components.
    1. Remove the A/C compressor and bracket. Set the compressor aside without disconnecting the lines.
    2.  
    3. If equipped, remove the vacuum pump and bracket. Set the pump aside without disconnecting the lines.
    4.  
    5. Disconnect the ground strap from the cowl.
    6.  
    7. If equipped, remove the turbocharger.
    8.  

  20.  
  21. To remove the left cylinder head, remove the following components.
    1. Remove the power steering pump. Set the pump aside without disconnecting the lines.
    2.  
    3. Remove the alternator and the bracket.
    4.  
    5. Remove the left side engine accessory bracket, the wiring harness at the clips, the glow plug relay and the dipstick tube.
    6.  

  22.  
  23. Unplug the coolant sensor from the head.
  24.  
  25. Unplug the glow plug wires. If your vehicle equipped with a turbocharger, you may need tool J 39083 or its equivalent to unplug the connections as they cannot usually be reached by hand. Do not pull on the wires.
  26.  

Before removing the rocker arm assemblies, mark the location of the rocker arm and pushrods etc. As they must be installed in their original positions.

  1. Remove the rocker arm assemblies.
  2.  
  3. Remove the radiator, bypass and heater hoses.
  4.  
  5. Remove the ground straps and the coolant crossover pipe/thermostat housing assembly.
  6.  
  7. Remove the exhaust manifold.
  8.  
  9. Remove the head bolts.
  10.  
  11. Remove the cylinder head.
  12.  

To install:
  1. Clean the mating surfaces of the head and block thoroughly.
  2.  
  3. Install a new head gasket on the engine block. Do NOT coat the gaskets with any sealer on either engine. The gaskets have a special coating that eliminates the need for sealer. The use of sealer will interfere with this coating and cause leaks. Install the cylinder head onto the block.
  4.  
  5. Clean the head bolts thoroughly. The left rear head bolt must be installed into the head prior to head installation. Coat the threads and heads of the head bolts with sealing compound (GM part #1052080 or equivalent) before installation. On 1988-95 models, tighten the head bolts in three stages: 20 ft. lbs. (25 Nm); 50 ft. lbs. (68 Nm) and finally, 1 / 4 or 90° turn more. On 1996-98 models, tighten the head bolts in three stages: 20 ft. lbs. (25 Nm); 55 ft. lbs. (75 Nm) and finally, 1 / 4 or 90° turn more.
  6.  
  7. Install the coolant crossover pipe and thermostat. Tighten the bolts to 31 ft. lbs. (42 Nm).
  8.  
  9. Install the ground strap.
  10.  
  11. Install the radiator, heater and bypass hoses.
  12.  
  13. Install the pushrods and the rocker arm assemblies in their original positions.
  14.  
  15. Attach the glow plug wires. If the engine is equipped with a turbocharger, you may need tool J 39383 or its equivalent to attach the connectors.
  16.  
  17. Attach the coolant sensor wire.
  18.  
  19. To install the right cylinder head, install the following components.
    1. Install the A/C compressor and bracket.
    2.  
    3. If equipped, install the vacuum pump and bracket.
    4.  
    5. Connect the ground strap to the cowl.
    6.  
    7. If equipped, install the turbocharger.
    8.  

  20.  
  21. To install the left cylinder head, install the following components.
    1. Install the power steering pump.
    2.  
    3. Install the alternator and the bracket.
    4.  
    5. Install the left side engine accessory bracket, the wiring harness at the clips, the glow plug relay and the dipstick tube.
    6.  

  22.  
  23. Raise the truck and support it with jack stands.
  24.  
  25. Attach the exhaust pipe to the exhaust manifold.
  26.  
  27. Lower the truck.
  28.  
  29. Install the rocker arm cover(s).
  30.  
  31. Install the fuel injection lines.
  32.  
  33. Install the intake manifold.
  34.  
  35. Fill the cooling system and connect the battery cables.
  36.  



Click image to see an enlarged view

Fig. Fig. 9: Cylinder head bolt tightening sequence-6.2L engines



Click image to see an enlarged view

Fig. Fig. 10: Cylinder head bolt tightening sequence-6.5L engines

7.4L Engines

See Figure 11

  1. Disconnect the negative battery cable and drain the cooling system.
  2.  
  3. Remove the intake manifold.
  4.  
  5. If removing the right cylinder head, remove the alternator and bracket.
  6.  
  7. Remove the AIR pump, if equipped.
  8.  
  9. If the vehicle is equipped with air conditioning, remove the air conditioning compressor and the forward mounting bracket and lay the compressor aside. Do not disconnect any of the refrigerant lines.
  10.  
  11. Remove the exhaust manifold(s).
  12.  
  13. Remove the spark plugs.
  14.  
  15. Remove the rocker arm cover.
  16.  



Click image to see an enlarged view

Fig. Fig. 11: Cylinder head bolt tightening sequence- 7.4L engines

  1. Remove the AIR pipes at the rear of the head, if equipped.
  2.  
  3. Disconnect the ground strap at the rear of the head.
  4.  
  5. Disconnect the temperature sensor wire.
  6.  
  7. Back off the rocker arm nuts and pivot the rocker arms out of the way so that the pushrods can be removed. Identify the pushrods so that they can be installed in their original positions.
  8.  
  9. Remove the cylinder head bolts and remove the heads.
  10.  

To install:
  1. Thoroughly clean the mating surfaces of the head and block. Clean the bolt holes thoroughly.
  2.  
  3. Install the cylinder heads using new gaskets. Install the gaskets with the word HEAD up.
  4.  

Coat a steel gasket on both sides with sealer. If a composition gasket is used, do not use sealer.

  1. Clean the bolts, apply sealer to the threads, and install them hand-tight.
  2.  
  3. Tighten the head bolts a little at a time in the sequence shown. Tighten the bolts in three stages: 30 ft. lbs. (40 Nm), 60 ft. lbs. (80 Nm) and finally to 85 ft. lbs. (115 Nm).
  4.  
  5. Install the pushrods.
  6.  
  7. Install the rocker arms and adjust them as described in this section.
  8.  
  9. Connect the temperature sensor wire.
  10.  
  11. Install the rocker arm cover.
  12.  
  13. Install the spark plugs.
  14.  
  15. Install the exhaust manifold(s).
  16.  
  17. If removed, connect the ground strap at the rear of the head.
  18.  
  19. If equipped, install the AIR pipes at the rear of the head.
  20.  
  21. If equipped, install the air conditioning compressor and the forward mounting bracket.
  22.  
  23. If equipped, install the AIR pump.
  24.  
  25. If removed, install the alternator and brackets.
  26.  
  27. Install the intake manifold.
  28.  
  29. Connect the battery cable and refill the cooling system.
  30.  

 
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