Engine Coolant Thermostat Replacement 4.3L Engine

1. Drain the cooling system. Refer to Cooling System Draining and Filling .
2. Loosen the air cleaner outlet duct clamp at the mass airflow/intake air temperature (MAF/IAT) sensor.



3. Remove the positive crankcase ventilation (PCV) hose.



4. Remove the air cleaner adapter nut.



5. In order to remove the air cleaner outlet duct, pivot the duct upward until the hinge clip releases from the lip on the throttle body.



6. Reposition the inlet hose clamp at the water outlet.
7. Remove the inlet hose from the water outlet.



8. Remove the water outlet studs.



9. Remove the water outlet.



10. Remove the thermostat.
11. Clean the sealing surface of the water outlet.
12. Clean the sealing surface of the intake manifold.
13. Remove and discard the O-ring seal.

1. Install a NEW O-ring seal to the thermostat.
2. Install the thermostat.



3. Install the water outlet.




Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

4. Install the water outlet studs.

Tighten
Tighten the studs to 25 N·m (18 lb ft).




5. Install the inlet hose to the water outlet.
6. Position the inlet hose clamp at the water outlet.



7. Align the hinge clip with the lip on the throttle body.

In order to install the air cleaner outlet duct, pivot the air cleaner outlet duct downward until the mounting stud is through the hole.




8. Install the air cleaner adapter nut.



9. Install the PCV hose.



10. Tighten the air cleaner outlet duct clamp at the MAF/IAT sensor.
11. Fill the cooling system. Refer to Cooling System Draining and Filling .
12. Inspect the cooling system for leaks.

Engine Coolant Thermostat Replacement 8.1L Engine

1. Drain the cooling system. Refer to Cooling System Draining and Filling .
2. Reposition the inlet hose clamp at the water outlet.
3. Remove the inlet hose from the water outlet.



4. Remove the water outlet bolts (2).
5. Remove the water outlet (1).
6. Remove the thermostat (3).

1. Install the thermostat (3).
2. Install the water outlet (1).

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

3. Install the water outlet bolts (2).

Tighten
Tighten the bolts to 30 N·m (22 lb ft).




4. Install the inlet hose to the water outlet.
5. Position the inlet hose clamp at the water outlet.
6. Fill the cooling system. Refer to Cooling System Draining and Filling .

Engine Coolant Thermostat Replacement 6.6L (LB7) Engine

1. Remove the water outlet. Refer to Water Outlet Tube Replacement .
2. Remove the bolt for the fuel line bracket.
3. Remove the thermostat housing cover bolts.
4. Remove the thermostats 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 with the vent valves towards the rear of engine.




2. Install the thermostat housing cover.

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

3. Install the thermostat housing cover bolts.

Tighten
Tighten the bolts to 21 N·m (15 lb ft).

4. Install the fuel line bracket bolt.

Tighten
Tighten the bolt to 21 N·m (15 lb ft).

5. Install the water outlet. Refer to Water Outlet Tube Replacement .

Engine Coolant Thermostat Replacement 6.6L (LLY) Engine

1. Remove the water outlet. Refer to Water Outlet Tube Replacement .
2. Remove the bolt for the fuel line bracket.
3. Remove the fuel line bracket.
4. Remove the thermostat housing cover bolts.
5. Remove the thermostat housing cover.
6. Remove the thermostats 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 with the vent valves towards the rear of engine.

Notice: Refer to Fastener Notice in the Preface section.




2. Install the thermostat housing cover.
3. Install the thermostat housing cover bolts.

Tighten
Tighten the bolts to 21 N·m (15 lb ft).

4. Install the fuel line bracket.
5. Install the fuel line bracket bolt.

Tighten
Tighten the bolt to 21 N·m (15 lb ft).

6. Install the water outlet tube. Refer to Water Outlet Tube Replacement .