Thermostat: Service and Repair

Engine Coolant Thermostat Replacement (LS4)

Special Tools

J 38185 Hose Clamp Pliers

Removal Procedure




1. Remove the radiator air lower baffle and deflector. Refer to Radiator Air Lower Baffle and Deflector Replacement (Service and Repair).
2. Reposition the radiator inlet hose. Refer to Radiator Inlet Hose Replacement (LS4) (Service and Repair).
3. Partially drain the cooling system. Refer to Cooling System Draining and Filling (LS4 GE47716 Fill) (Service and Repair)Cooling System Draining and Filling (LS4 Static Fill) (Service and Repair).
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. Remove the water outlet housing bolts (302).
7. Remove the water outlet housing (303) and O-ring seal (304).
8. Remove the thermostat (305).
9. Clean and inspect the water outlet housing O-ring seal mating surfaces.

Installation Procedure

Notice: 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.




1. Install the thermostat (305).
2. Install the O-ring seal (304) and water outlet housing (303).

Notice: Refer to Fastener Notice.

3. Install the water outlet housing bolts (302).

Tighten the bolts to 15 N.m (11 lb ft).




4. Install the radiator inlet hose to the water outlet housing.
5. Use the J 38185 in order to reposition and install the hose clamp to the water outlet housing.
6. Fill the cooling system. Refer to Cooling System Draining and Filling (LS4 GE47716 Fill) (Service and Repair)Cooling System Draining and Filling (LS4 Static Fill) (Service and Repair).
7. Install the radiator inlet hose. Refer to Radiator Inlet Hose Replacement (LS4) (Service and Repair).
8. Install the radiator air lower baffle and deflector. Refer to Radiator Air Lower Baffle and Deflector Replacement (Service and Repair).