GM Service Manual Online
For 1990-2009 cars only

Engine Coolant Thermostat Replacement LS4

Special Tools

J 38185 Hose Clamp Pliers

Removal Procedure


    Object Number: 1524229  Size: SH
  1. Remove the radiator air lower baffle and deflector. Refer to Radiator Air Lower Baffle and Deflector Replacement.
  2. Reposition the radiator inlet hose. Refer to Radiator Inlet Hose Replacement.
  3. Partially drain the cooling system. Refer to Cooling System Draining and Filling.
  4. Use the J 38185 in order to reposition the hose clamp from the water outlet housing.
  5. Remove the radiator inlet hose from the water outlet housing.

  6. Object Number: 1411896  Size: SH
  7. Remove the water outlet housing bolts (302).
  8. Remove the water outlet housing (303) and O-ring seal (304).
  9. Remove the thermostat (305).
  10. Clean and inspect the water outlet housing O-ring seal mating surfaces.

Installation Procedure

Caution: DO NOT use cooling system seal tabs, or similar compounds, unless otherwise instructed. The use of cooling system seal tabs, or similar compounds, may restrict coolant flow through the passages of the cooling system or the engine components. Restricted coolant flow may cause engine overheating and/or damage to the cooling system or the engine components/assembly.


    Object Number: 1411896  Size: SH
  1. Install the thermostat (305).
  2. Install the O-ring seal (304) and water outlet housing (303).
  3. Caution: Refer to Fastener Caution in the Preface section.

  4. Install the water outlet housing bolts (302).
  5. Tighten
    Tighten the bolts to 15 N·m (11 lb ft).


    Object Number: 1524229  Size: SH
  6. Install the radiator inlet hose to the water outlet housing.
  7. Use the J 38185 in order to reposition and install the hose clamp to the water outlet housing.
  8. Fill the cooling system. Refer to Cooling System Draining and Filling.
  9. Install the radiator inlet hose. Refer to Radiator Inlet Hose Replacement.
  10. Install the radiator air lower baffle and deflector. Refer to Radiator Air Lower Baffle and Deflector Replacement.

Engine Coolant Thermostat Replacement LZE, LZ4, LZG

Removal Procedure


    Object Number: 1613134  Size: SH
  1. Drain the cooling system. Refer to Cooling System Draining and Filling.
  2. Remove the air cleaner outlet duct. Refer to Air Cleaner Outlet Duct Replacement or Air Cleaner Outlet Duct Replacement.
  3. Reposition the radiator outlet hose clamp at the thermostat housing.
  4. Remove the radiator outlet hose from the thermostat housing (3.5L shown, 3.9L similar).

  5. Object Number: 1556817  Size: SH
  6. Remove the thermostat housing bolt/stud.
  7. Remove the thermostat housing and gasket.
  8. Remove the thermostat.
  9. Clean the gasket surfaces.

Installation Procedure


    Object Number: 1556817  Size: SH
  1. Install a NEW thermostat.
  2. Position a NEW gasket and the thermostat housing to the engine block.
  3. Caution: Refer to Fastener Caution in the Preface section.

  4. Install the thermostat housing bolt/stud.
  5. Tighten
    Tighten the bolt/stud to 10 N·m (89 lb in).


    Object Number: 1613134  Size: SH
  6. Install the radiator outlet hose to the thermostat housing (3.5L shown, 3.9L similar).
  7. Position the radiator outlet hose clamp at the thermostat housing.
  8. Install the air cleaner outlet duct. Refer to Air Cleaner Outlet Duct Replacement or Air Cleaner Outlet Duct Replacement.
  9. Fill the cooling system. Refer to Cooling System Draining and Filling.
  10. Inspect the system for leaks.