GM Service Manual Online
For 1990-2009 cars only

Engine Coolant Thermostat Replacement 2.0L

Removal Procedure


    Object Number: 1255563  Size: SH

    Caution: As long as there is pressure in the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the pressure cap while the engine is hot and pressure is high will cause the solution to boil instantaneously -- possibly with explosive force -- spewing the solution over the engine, fenders and the person removing the cap.

  1. Drain the coolant. Refer to Cooling System Draining and Filling .
  2. Loosen the hose clamp on the upper radiator hose at the thermostat housing.
  3. Disconnect the upper radiator hose from the thermostat housing.

  4. Object Number: 1255564  Size: SH
  5. Remove the mounting bolts that hold the thermostat housing to the cylinder head.
  6. Remove the thermostat housing from the cylinder head.

  7. Object Number: 1255540  Size: SH
  8. Remove the O-Ring seal from the thermostat housing.
  9. Remove the thermostat from the thermostat housing by pressing the thermostat mounting flange downward and then rotating the flange clockwise.
  10. Inspect the valve seat for foreign matter that could prevent the valve from sealing properly.
  11. Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis .
  12. Clean the thermostat housing and the cylinder head mating surfaces.

Installation Procedure


    Object Number: 1255540  Size: SH
  1. Install the thermostat into the thermostat housing by pressing the thermostat mounting flange downward and then rotating the flange counterclockwise. Rotate the thermostat mounting flange until it is seated in the thermostat housing recesses.
  2. Coat the sealing surface of the new O-ring seal with Lubriplate®.
  3. Install the new O-ring seal into the recess in the thermostat housing.

  4. Object Number: 1255564  Size: SH
  5. Install the thermostat housing to the cylinder head.
  6. Notice: Refer to Fastener Notice in the Preface section.

  7. Secure the thermostat housing to the cylinder head with the mounting bolts.
  8. Tighten
    Tighten the thermostat housing mounting bolts to 15 N·m (11 lb ft).


    Object Number: 1255563  Size: SH
  9. Connect the upper radiator hose to the thermostat housing.
  10. Secure the upper radiator hose to the thermostat housing with a hose clamp.
  11. Refill the engine cooling system. Refer to Cooling System Draining and Filling .

Engine Coolant Thermostat Replacement 2.5L

Removal Procedure


    Object Number: 1375415  Size: SH

    Caution: As long as there is pressure in the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the pressure cap while the engine is hot and pressure is high will cause the solution to boil instantaneously -- possibly with explosive force -- spewing the solution over the engine, fenders and the person removing the cap.

  1. Drain the coolant. Refer to Cooling System Draining and Filling .
  2. Loosen the hose clamp on the upper radiator hose at the thermostat housing.
  3. Disconnect the coolant hose from the thermostat housing.

  4. Object Number: 1375416  Size: SH
  5. Remove the mounting bolts that hold the thermostat housing to the cylinder head.
  6. Remove the thermostat housing from the cylinder head.
  7. Remove the O-ring seal from the thermostat housing.
  8. Inspect the valve seat for foreign matter that could prevent the valve from sealing properly.
  9. Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis .
  10. Clean the thermostat housing and the cylinder head mating surfaces.

Installation Procedure


    Object Number: 1375416  Size: SH
  1. Coat the sealing surface of the new O-ring seal with Lubriplate®.
  2. Install the new O-ring seal into the recess in the thermostat housing.
  3. Install the thermostat housing to the cylinder head.
  4. Notice: Refer to Fastener Notice in the Preface section.

  5. Secure the thermostat housing to the cylinder head with the mounting bolts.
  6. Tighten
    Tighten the thermostat housing mounting bolts to 10 N·m (89 lb in).


    Object Number: 1375415  Size: SH
  7. Connect the coolant hose to the thermostat housing.
  8. Secure the coolant hose to the thermostat housing with a hose clamp.
  9. Refill the engine cooling system. Refer to Cooling System Draining and Filling .