GM Service Manual Online
For 1990-2009 cars only

Tools Required

J 43271

Clamp Pliers

Removal Procedure

    Notice: The thermostat will not function correctly once it is contacted by oil. If oil is found in the cooling system, it must be flushed and the thermostat's cartridge replaced.


    Object Number: 931332  Size: SH
  1. Remove the coolant cap from the surge tank.
  2. Place a coolant container under the radiator drain valve at the right hand side of the radiator tank.
  3. Using a flat-bladed screwdriver, open the valve and drain the coolant.
  4. Raise the vehicle on a hoist.

  5. Object Number: 964352  Size: SH

    Important: A drain plug has been provided at the bottom of the water pump for engine block coolant drainage.

  6. Drain the coolant from the engine block at the water pump drain plug. After the coolant has drained, tighten the plug.
  7. Lower the vehicle.
  8. Remove the battery box. Refer to Battery Box Replacement .

  9. Object Number: 931384  Size: SH
  10. Disconnect the radiator hose and clamp from the thermostat pipe assembly using the J 43271 Clamp Pliers, or equivalent.

  11. Object Number: 931368  Size: SH
  12. Disconnect the return hose and clamp from the thermostat housing pipe.
  13. Remove the attachment bolt from the thermostat bracket assembly to thermostat pipe assembly near the front of the engine.

  14. Object Number: 951386  Size: SH
  15. Remove the exhaust heat shield bolts.
  16. Remove the exhaust heat shield.
  17. Disconnect the electrical connector at the coolant temperature sensor.
  18. Disconnect the O2 sensor connector and clip from the bracket.

  19. Object Number: 931420  Size: SH
  20. Disconnect the coolant hoses and clamps at the thermostat housing pipes.

  21. Object Number: 951404  Size: SH
  22. Remove the thermostat housing bolts to the engine.
  23. Important: Twist the water pipe while pulling to remove it from the water pump.

  24. Remove the water pipe from the thermostat housing.
  25. Remove the thermostat housing assembly from the vehicle.

  26. Object Number: 951792  Size: SH
  27. Remove the water transfer pipe O-seals and discard.
  28. Remove the thermostat housing cover bolts and cover.
  29. Remove and discard the thermostat housing O-seal.
  30. Remove the thermostat cartridge and inner sleeve from the thermostat housing.
  31. Remove all debris and thread sealant from the engine coolant temperature sensor and bolt holes if the housing is being re-used.

Installation Procedure


    Object Number: 951651  Size: SH
  1. Install the thermostat cartridge into the thermostat housing while aligning the cartridge tangs up with the thermostat housing bolt holes. This will assure the inner sleeve can be completely installed.

  2. Object Number: 951659  Size: SH
  3. Align and insert the inner sleeve notch into the thermostat housing. If the inner sleeve notch is not properly positioned, the sleeve will not completely seat into the housing.

  4. Object Number: 951626  Size: SH
  5. Install a new thermostat housing cover seal into the recess groove.
  6. Notice: Refer to Fastener Notice in the Preface section.

  7. Install the thermostat housing cover bolts.
  8. Tighten
    Tighten the Thermostat housing cover-to-thermostat housing bolts to 10 N·m (89 lb in).

  9. Install a new thermostat housing to engine seal onto the thermostat housing.
  10. Load the thermostat housing assembly into position while the vehicle is lowered.
  11. Raise the vehicle.

  12. Object Number: 951611  Size: SH

    Important: The water feed pipe seals can be lightly lubricated with silicone gel to aid during installation.

  13. Install new O-seals onto the water feed pipe.
  14. Install the water feed pipe into the thermostat housing aligning locator tab.
  15. Align the water pipe to water pump.
  16. Seat the water feed O-seal by pushing inward toward the water pump. Take care not to tear or damage the O-ring.
  17. Lower the vehicle.

  18. Object Number: 951404  Size: SH
  19. Position the thermostat housing against the engine. Be sure that the thermostat housing pipe is properly positioned against the support bracket near the front of the engine.
  20. Install the thermostat housing to block bolts.
  21. Tighten
    Tighten the thermostat housing-to-block bolts to 10 N·m (89 lb in).

  22. Install the thermostat pipe bracket-to-engine bolt.
  23. Tighten
    Tighten the thermostat pipe bracket-to-cylinder head bolt to 8 N·m (71 lb in).


    Object Number: 951591  Size: SH
  24. Connect the electrical connector to coolant sensor.
  25. Connect the O2 sensor connector and re-attach the connector to the bracket.

  26. Object Number: 931420  Size: SH
  27. Connect the coolant hoses to the thermostat housing and reposition the clamps, upper heater hose connects to the pipe nearest the shift cable.

  28. Object Number: 931384  Size: SH
  29. Connect the lower radiator hose and clamp.
  30. Connect the return hose to the thermostat pipe.

  31. Object Number: 951395  Size: SH
  32. Install the exhaust manifold heat shield.
  33. Install the exhaust manifold shield bolts.
  34. Tighten
    Tighten the exhaust manifold heat shield bolts to 23 N·m (17 lb ft).


    Object Number: 951451  Size: SH
  35. Install the battery box. Refer to Battery Box Replacement .

  36. Object Number: 931332  Size: SH

    Important: The vehicle must be level when filling the cooling system.

  37. Verify the drain valves at the radiator and water pump are closed.

  38. Object Number: 931323  Size: SH
  39. Fill the engine coolant. Refer to Cooling System Draining and Filling .
  40. Verify the repair and inspect for any leaks.