Thermostat: Service and Repair

Engine Coolant Thermostat Replacement (6.6L (LLY/LBZ))

Removal Procedure

1. Remove the upper fan shroud. Refer to Engine Coolant Fan Upper Shroud Replacement (4.3L, 4.8L, 5.3L, 6.0L, 6.2L, 7.0L) (Service and Repair)Engine Coolant Fan Upper Shroud Replacement (6.6L) (Service and Repair).
2. Remove the intake manifold. Refer to Intake Manifold Tube Replacement (LMM) (Service and Repair).
3. Drain the cooling system. Refer to Cooling System Draining and Filling (Static Fill) (Service and Repair)Cooling System Draining and Filling (Vac N Fill) (Service and Repair).




4. Compress the clamp and disconnect the radiator inlet hose from the thermostat housing.




5. Remove the fuel line bracket bolt and position the fuel line aside.




6. Compress the clamp and disconnect the turbocharger cooling inlet pipe from the thermostat housing.




7. Remove the 4 bolts and the thermostat housing.
8. Remove the thermostat and seals.

Inspection Procedure

1. Inspect the thermostats for sticking, cracks, and/or leakage of wax.
2. Replace the thermostats if damage is found.
3. Clean the thermostat housing and thermostat housing cover sealing surfaces.

Installation Procedure




1. Install the thermostats and seals to the thermostat housing.
The rear thermostat (4) has 2 vent valves. Install the vent valves towards the rear of the engine.





Caution: Refer to Fastener Caution (Fastener Caution).

2. Position the thermostat housing and install the 4 bolts and tighten to 21 Nm (15 lb ft).




3. Compress the clamp and connect the turbocharger cooling inlet pipe to the thermostat housing.




4. Position the fuel line to the thermostat housing and install the fuel line bracket bolt and tighten to 21 Nm (15 lb ft).




5. Compress the clamp and connect the radiator inlet hose to the thermostat housing.
6. Install the intake manifold tube. Refer to Intake Manifold Tube Replacement (LMM) (Service and Repair).
7. Install the upper fan shroud. Refer to Engine Coolant Fan Upper Shroud Replacement (4.3L, 4.8L, 5.3L, 6.0L, 6.2L, 7.0L) (Service and Repair)Engine Coolant Fan Upper Shroud Replacement (6.6L) (Service and Repair).
8. Fill the cooling system. Refer to Cooling System Draining and Filling (Static Fill) (Service and Repair)Cooling System Draining and Filling (Vac N Fill) (Service and Repair).