GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1998 🢒 Firebird 🢒 Engine 🢒 Engine Cooling 🢒 Engine Coolant Thermostat Replacement

Engine Coolant Thermostat Replacement 3.8L V6

Removal Procedure
  1. Open the radiator drain cock. Drain the engine coolant from the radiator to a level below the thermostat.
  2. Close the radiator drain cock.

    3. Tighten
    Tighten the radiator drain cock to 1.5 N·m (13 lb in).


    Object Number: 221704 Size: SH
  3. Disconnect the EGR valve electrical connector.

    4. Object Number: 221706 Size: SH
  4. Remove the EGR valve outlet pipe bolt from the upper intake.
  5. Remove the EGR valve outlet pipe nut from the EGR valve adapter.
  6. Remove the EGR valve outlet pipe.

    7. Object Number: 11686 Size: SH
  7. Loosen the hose clamp (3).
  8. Remove the inlet hose (4) from the water outlet (2).
  9. Remove the water outlet bolts (1).
  10. Remove the water outlet (2).
  11. Remove the water outlet gasket (6).
  12. Remove the engine coolant thermostat (5).
  13. Clean the gasket surfaces of the water outlet and upper intake manifold.

Installation Procedure

    Object Number: 11686 Size: SH
  1. Install the engine coolant thermostat (5) into the upper intake manifold.
  2. Install a new water outlet gasket (6).
  3. Install the water outlet (2).
  4. Install the water outlet bolts (1).

    5. Tighten
    Tighten the water outlet bolts (1) to 27 N·m (20 lb ft).

  5. Install the inlet hose (4) to the water outlet (2).
  6. Install the hose clamp (3).

    7. Object Number: 221706 Size: SH
  7. Install the EGR valve outlet pipe.
  8. Install the EGR valve outlet pipe nut to the EGR valve adapter.
  9. Install the EGR valve outlet pipe bolt to the upper intake.

    10. Tighten

        • Tighten the EGR valve outlet pipe bolt to the upper intake to 29 N·m (21 lb ft).
        • Tighten the EGR valve outlet pipe nut to the EGR valve adapter to 29 N·m (21 lb ft).
        • Add engine coolant.

           Notice: When adding coolant, use DEX-COOL® coolant. If silicated coolant is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner-at 50 000 km (30,000 mi) or 24 months.

        • Start the engine.
        • After the engine reaches normal operating temperature, inspect for coolant leaks.

Engine Coolant Thermostat Replacement 5.7L V8

Removal Procedure
  1. Open the radiator drain cock. Drain the engine coolant from the radiator to a level below the thermostat.
  2. Close the radiator drain cock.

    3. Tighten
    Tighten the radiator drain cock to 1.5 N·m (13 lb in).


    Object Number: 221671 Size: SH
  3. Reposition the radiator outlet hose clamp at the thermostat housing.
  4. Remove the radiator outlet hose from the thermostat housing.

    5. Object Number: 221708 Size: SH
  5. Remove the thermostat housing bolts.

    6. Object Number: 221709 Size: SH
  6. Remove the thermostat housing and note position of thermostat.
  7. Remove the thermostat housing gasket.
  8. Remove the thermostat.

Installation Procedure

    Object Number: 221709 Size: SH
  1. Thoroughly clean the thermostat housing and water pump gasket surfaces.
  2. Install the thermostat gasket with the taper up.
  3. Install the thermostat.
  4. Install the thermostat housing.

    5. Object Number: 221708 Size: SH
  5. Install the thermostat housing bolts.

    6. Tighten
    Tighten the thermostat housing bolts to 15 N·m (11 lb ft).


    Object Number: 221671 Size: SH
  6. Install the radiator outlet hose to the thermostat housing.
  7. Position the radiator outlet hose clamp at the thermostat housing.
  8. Add engine coolant.

    9. Notice: When adding coolant, use DEX-COOL® coolant. If silicated coolant is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner-at 50 000 km (30,000 mi) or 24 months.

  9. Start the engine.
  10. After the engine reaches normal operating temperature, inspect for coolant leaks.