GM Service Manual Online
For 1990-2009 cars only

Thermostat Housing Crossover Replacement 6.6L Engine

Removal Procedure


    Object Number: 813243  Size: SH
  1. Loosen the outlet duct clamp at the upper intake manifold cover.
  2. Remove the upper intake manifold cover from the outlet duct.
  3. Remove the upper intake manifold cover.
  4. Drain the cooling system. Refer to Cooling System Draining and Filling .
  5. Disconnect the negative battery cables. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  6. Remove the upper fan shroud. Refer to Engine Coolant Fan Upper Shroud Replacement .
  7. Remove the drive belt. Refer to Drive Belt Replacement in Engine Mechanical - 6.6L.

  8. Object Number: 674573  Size: SH
  9. Disconnect the air conditioning (A/C) compressor clutch electrical connector (5).
  10. Disconnect the A/C cut out switch electrical connector.

  11. Object Number: 652573  Size: SH
  12. Remove the A/C compressor bolts.
  13. Move the A/C compressor with the hoses attached to the right side of the engine compartment.

  14. Object Number: 666693  Size: SH
  15. Remove the generator positive cable to generator nut.
  16. Remove the positive cable from the generator.
  17. Remove the clip holding the positive cable to the engine front cover.
  18. Remove the battery positive cable junction block to power steering pump bolt.
  19. Move the generator positive cable and the junction block bracket aside.

  20. Object Number: 674573  Size: SH
  21. Disconnect the generator electrical connector (1).
  22. Disconnect the engine coolant temperature (ECT) sensor electrical connector.

  23. Object Number: 669241  Size: SH
  24. Remove the power steering pump bracket and secure to the side.
  25. • Do not remove the power steering pump from the bracket.
    • The hoses and battery cables can remain on the power steering pump.

    Object Number: 698198  Size: SH
  26. Remove the fuel bleed valve and positive crankcase ventilation (PCV) oil separator bracket bolt from the generator bracket.

  27. Object Number: 669244  Size: SH
  28. Remove the heater outlet hose bracket bolt from the generator bracket.
  29. Remove the ribbed idler pulley.
  30. Remove the generator bracket and position to the side.
  31. • The generator does not require removal.
    • The drive belt tensioner does not require removal.
  32. Remove the oil fill tube. Refer to Oil Filler Tube Replacement in Engine Mechanical - 6.6L.
  33. Remove the water outlet. Refer to Water Outlet Tube Replacement .

  34. Object Number: 699325  Size: SH
  35. Remove the heater inlet pipe to fuel filter bolt.
  36. Remove the heater inlet pipe with O-ring seal from the crossover.

  37. Object Number: 699335  Size: SH
  38. Remove the turbocharger coolant return pipe clamps and hose.
  39. Remove the fuel line bracket from the thermostat housing crossover.
  40. Remove the cooling fan pulley. Refer to Cooling Fan Pulley Replacement .

  41. Object Number: 654526  Size: SH
  42. Remove the thermostat housing bolts and nuts from the left cylinder head.
  43. Remove the thermostat housing bolts and nuts from the right cylinder head.
  44. Remove the bypass pipe to water pump bolts.
  45. Remove the thermostat housing with the bypass pipe.
  46. Remove the bypass pipe to water pump O-ring.

  47. Object Number: 660428  Size: SH
  48. Remove the bypass pipe from the thermostat housing.
  49. Remove the O-ring from the bypass pipe.

  50. Object Number: 660424  Size: SH
  51. Remove the thermostat cover bolts.
  52. Remove the thermostat cover.
  53. Remove the thermostats with seals.
  54. Remove the thermostat seals.
  55. If required, clean and inspect the thermostat housing. Refer to Engine Coolant Thermostat Housing Cleaning and Inspection in Engine Mechanical - 6.6L.

Installation Procedure


    Object Number: 660424  Size: SH
  1. Install the thermostats with the seals.
  2. The thermostat with the vent valves goes toward the rear of the engine. Install with the vent valves towards the rear of the engine.

  3. Install the thermostat cover and gasket.
  4. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  5. Install the thermostat cover bolts.
  6. Tighten
    Tighten the bolts to 21 N·m (15 lb ft).


    Object Number: 660428  Size: SH
  7. Install a new O-ring to the bypass pipe. Lubricate the O-ring with coolant.
  8. Install the bypass pipe to the thermostat housing crossover.

  9. Object Number: 654526  Size: SH
  10. Install NEW thermostat housing gaskets.
  11. Install a NEW O-ring for the bypass pipe to the water pump.
  12. Install the thermostat housing with the bypass pipe.
  13. Install the bypass pipe to water pump bolts.
  14. Tighten
    Tighten the bolts to 21 N·m (15 lb ft).

  15. Install the thermostat housing bolts and nuts.
  16. Tighten
    Tighten the bolts and nuts to 21 N·m (15 lb ft).

  17. Install the fuel line bracket and bolt.
  18. Tighten
    Tighten the bolt to 21 N·m (15 lb ft).


    Object Number: 699335  Size: SH
  19. Install the turbocharger coolant return pipe hose and clamps.
  20. Install the cooling fan pulley. Refer to Cooling Fan Pulley Replacement .

  21. Object Number: 699325  Size: SH
  22. Install a NEW O-ring seal to the heater inlet pipe.
  23. Install the heater inlet pipe to the thermostat housing crossover.
  24. Install the heater inlet pipe to thermostat housing crossover bolt.
  25. Tighten
    Tighten the bolt to 21 N·m (15 lb ft).

  26. Install the heater inlet pipe to fuel filter bolt.
  27. Tighten
    Tighten the bolt to 21 N·m (15 lb ft).


    Object Number: 669244  Size: SH
  28. Install the generator bracket and bolts.
  29. Tighten
    Tighten the bolts to 50 N·m (37 lb ft).

  30. Install the ribbed idler pulley and the bolt.
  31. Tighten
    Tighten the bolt to 43 N·m (32 lb ft).

  32. Install the heater outlet hose bracket bolt.
  33. Tighten
    Tighten the bolt to 21 N·m (15 lb ft).


    Object Number: 698198  Size: SH
  34. Install the fuel bleed valve and PCV oil separator bracket nuts to the generator bracket.
  35. Tighten
    Tighten the nuts to 25 N·m (18 lb ft).


    Object Number: 669241  Size: SH
  36. Install the power steering pump bracket and bolts.
  37. Tighten
    Tighten the bolts to 46 N·m (34 lb ft).

  38. Install the water outlet. Refer to Water Outlet Tube Replacement .

  39. Object Number: 666693  Size: SH
  40. Position the generator positive cable.
  41. Install the generator positive cable in the clip on the engine front cover.
  42. Install the generator positive cable nut.
  43. Tighten
    Tighten the nut to 9 N·m (80 lb in).

  44. Install the battery positive cable junction block bracket and bolt to the power steering pump.
  45. Tighten
    Tighten the bolt to 9 N·m (80 lb in).


    Object Number: 674573  Size: SH
  46. Connect the ECT sensor electrical connector.
  47. Connect the generator electrical connector (1).

  48. Object Number: 652573  Size: SH
  49. Position the A/C compressor.
  50. Install the A/C compressor bolts.
  51. Tighten
    Tighten the bolts to 50 N·m (37 lb ft).


    Object Number: 674573  Size: SH
  52. Connect the A/C cut out switch electrical connector.
  53. Connect the A/C compressor clutch electrical connector (5).
  54. Install the drive belt. Refer to Drive Belt Replacement in Engine Mechanical - 6.6L.
  55. Install the upper fan shroud. Refer to Engine Coolant Fan Upper Shroud Replacement .
  56. Fill the cooling system. Refer to Cooling System Draining and Filling .
  57. Connect the negative battery cables. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.

  58. Object Number: 813243  Size: SH
  59. Install the upper intake manifold cover.
  60. Install the upper intake manifold cover to the outlet duct.
  61. Tighten the outlet duct clamp at the upper intake manifold cover.
  62. Tighten
    Tighten the clamp to 6 N·m (53 lb in).