GM Service Manual Online
For 1990-2009 cars only

Engine Coolant Thermostat Replacement 2.2L

Removal Procedure

  1. Remove the necessary amount of coolant from the radiator. Refer to Cooling System Draining and Filling .
  2. Remove the upper radiator inlet hose.

  3. Object Number: 4150  Size: SH
  4. Remove the coolant outlet nuts.

  5. Object Number: 4149  Size: SH
  6. Remove the thermostat housing from the engine.
  7. Remove the thermostat gasket, if used.

  8. Object Number: 4148  Size: SH
  9. Remove the coolant thermostat.

Cleaning Procedure

    • Clean all the parts.
    • Clean all the sealing surfaces.

Installation Procedure


    Object Number: 4148  Size: SH
  1. Install the thermostat to the engine.
  2. Install the new thermostat gasket (if used). Otherwise, place a 3 mm (1/8 in) bead of RTV sealer in the groove of the coolant outlet sealing surface.

  3. Object Number: 4149  Size: SH
  4. Install the thermostat housing to the engine.

  5. Object Number: 4150  Size: SH

    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.

  6. Install the coolant outlet attaching nuts.
  7. Tighten
    Tighten the coolant outlet nuts to 10 N·m (89 lb in).

  8. Install the upper radiator inlet hose.
  9. Fill the cooling system with the specified coolant and concentration. Refer to Cooling System Draining and Filling .
  10. Inspect all of the sealing surfaces and the connections for leaks after starting the engine. Refer to Cooling System Leak Testing .

Engine Coolant Thermostat Replacement 4.3L

Removal Procedure

  1. Remove the necessary coolant from the radiator. Refer to Cooling System Draining and Filling .
  2. Remove the upper radiator inlet hose.

  3. Object Number: 42901  Size: SH
  4. Remove the coolant outlet bolts.

  5. Object Number: 42895  Size: SH
  6. Remove the coolant outlet from the lower intake manifold.
  7. Remove the thermostat gasket.

  8. Object Number: 42903  Size: SH
  9. Remove the coolant thermostat.
  10. Clean all the sealing surfaces of the coolant outlet.
  11. Clean the sealing surface on the lower intake manifold.

Installation Procedure


    Object Number: 42903  Size: SH
  1. Install the coolant thermostat in the lower intake manifold.
  2. Important: To prevent leakage, thoroughly clean all parts and sealing surfaces.


    Object Number: 42895  Size: SH
  3. Install a new gasket (if used). Otherwise, place a 3 mm (1/8 in) bead of RTV sealer at the groove on the coolant outlet sealing surface.
  4. Install the coolant outlet on the lower intake manifold.

  5. Object Number: 42901  Size: SH

    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.

  6. Install the attaching bolts.
  7. Tighten
    Tighten coolant outlet bolts to 19 N·m (14 lb ft).

  8. Install the radiator inlet hose.
  9. Fill the cooling system with specified coolant and concentration. Refer to Radiator Replacement .
  10. Inspect all sealing surfaces for leaks after starting the engine. Refer to Cooling System Leak Testing .