Thermostat: Service and Repair

Thermostat Replacement (RPO LS4)

Tools Required

J 38185 Hose Clamp Pliers

Removal Procedure




1. Partially drain the cooling system. Refer to Draining and Filling Cooling System (9C1, 9C3 Static Fill) Draining and Filling Cooling System (LS4 GE 47716 Fill) Draining and Filling Cooling System (LS4 Static Fill) Draining and Filling Cooling System (LZE, LZ4, LZ8, 9C1, 9C3, GE47716 Fill) Draining and Filling Cooling System (LZE, LZ4, LZ8 Static Fill).
2. Use the J 38185 in order to reposition the hose clamp from the water outlet housing.
3. Remove the radiator inlet hose from the water outlet housing.




4. Remove the water outlet housing bolts (302).
5. Remove the water outlet housing (303) and O-ring seal (304).
6. Remove the thermostat (305).
7. 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 Draining and Filling Cooling System (9C1, 9C3 Static Fill) Draining and Filling Cooling System (LS4 GE 47716 Fill) Draining and Filling Cooling System (LS4 Static Fill) Draining and Filling Cooling System (LZE, LZ4, LZ8, 9C1, 9C3, GE47716 Fill) Draining and Filling Cooling System (LZE, LZ4, LZ8 Static Fill).