GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1999 🢒 Firefly (Canada) 🢒 Engine 🢒 Engine Cooling 🢒 Engine Coolant Thermostat Replacement

Removal Procedure
  1. Drain the engine cooling system to a level below that of the thermostat housing. Refer to Cooling System Draining and Filling in Engine Cooling.

    2. Object Number: 185632 Size: SH
  2. For a 1.3L engine, release the hose clamp in order to remove the upper radiator hose at the thermostat housing cap (3).

    3. Object Number: 185630 Size: SH
  3. For a 1.0L engine, release the hose clamp in order to remove the upper radiator hose at the thermostat housing cap (4).
  4. Remove the two retaining bolts in order to remove the water outlet from the housing.
  5. Remove the thermostat and the gasket from the thermostat housing.

    6. Object Number: 167651 Size: SH
  6. Inspect the thermostat air bleed valve (2) in order to ensure that the valve (2) is clear. The engine could overheat if this valve becomes clogged.
  7. Inspect the valve seat for foreign objects that is preventing the valve from seating.
  8. Test the thermostat for proper operation. Refer to Thermostat Diagnosis in Engine Cooling.

Installation Procedure
  1. Install the thermostat and the new gasket to the housing.
  2. Install the water outlet to the housing.

    3. Object Number: 185632 Size: SH
  3. For a 1.3L engine, secure the hose with a hose clamp (3).

    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.

  4. Secure the water outlet to the housing (3) with two retaining bolts.

    5. Tighten
    Tighten the water outlet retaining bolts to 20 N·m (15 lb ft).

  5. Install the upper radiator hose to the thermostat cap.

    6. Object Number: 185630 Size: SH
  6. Secure the hose with a hose clamp (4), for a 1.0L engine.
  7. Refill the engine cooling system. Refer to Cooling System Draining and Filling in Engine Cooling.