Engine Coolant Thermostat Replacement 6.6L (LLY/LBZ)

1. Remove the upper fan shroud. Refer to Engine Coolant Fan Upper Shroud Replacement.
2. Remove the intake manifold. Refer to Intake Manifold Tube Replacement.
3. Drain the cooling system. Refer to Cooling System Draining and Filling.



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.

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.

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 in the Preface section.




2. Position the thermostat housing and install the 4 bolts and tighten to 21 N·m (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 N·m (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.
7. Install the upper fan shroud. Refer to Engine Coolant Fan Upper Shroud Replacement.
8. Fill the cooling system. Refer to Cooling System Draining and Filling.

Engine Coolant Thermostat Replacement 4.3L

1. Remove the air cleaner and the duct assembly. Refer to Air Cleaner Outlet Resonator Replacement.
2. Partially drain the coolant. Refer to Cooling System Draining and Filling.
3. Remove the coolant recovery reservoir. Refer to Coolant Recovery Reservoir Replacement.
4. Disconnect the radiator hose from the thermostat housing.



5. Remove the bolts attaching the thermostat housing to the thermostat.
6. Remove the thermostat housing.
7. Remove the thermostat.
8. Clean the gasket mating surfaces.

1. Install the thermostat.
2. Install the thermostat housing to the intake manifold.

Caution: Refer to Fastener Caution in the Preface section.

3. Install the bolts to the housing and tighten to 25 N·m (18 lb ft).



4. Connect the radiator hose to the thermostat housing.
5. Install the coolant recovery reservoir. Refer to Coolant Recovery Reservoir Replacement.
6. Install the air cleaner and the duct. Refer to Air Cleaner Outlet Resonator Replacement.
7. Refill the cooling system. Refer to Cooling System Draining and Filling.
8. Bleed the air from the cooling system.
9. Inspect the thermostat housing and the gasket for coolant leaks.