Engine Coolant Thermostat Replacement Gasoline Engines

1. Drain the coolant until the radiator coolant level is below the thermostats. Refer to Cooling System Draining and Filling .



2. On the 4.3L, remove the following items:

2.1.	The bolts or studs

2.2.	The coolant outlet

2.3.	The thermostat from the housing

2.4.	The gasket (If necessary)




3. On the 5.0L and the 5.7L, remove the following items:

3.1.	The bolts or studs

3.2.	The coolant outlet

3.3.	The thermostat from the housing

3.4.	The gasket (If necessary)




4. On the 7.4L, remove the following items:

4.1.	The bolts or studs

4.2.	The coolant outlet

4.3.	The thermostat from the housing

4.4.	The gasket (If necessary)

5. Clean the thermostat housing and the cooling outlet sealing surfaces.

1. For the 4.3L, install the following items:

1.1.	The thermostat into the housing

1.2.	The gasket (If necessary)

1.3.	The coolant 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.

2. Install the bolts or the studs

Tighten
Tighten the bolts or the studs to 28 N·m (21 lb ft).




3. For the 5.0L and the 5.7L, install the following items:

3.1.	The thermostat into the housing

3.2.	The gasket (If necessary)

3.3.	The coolant outlet

4. Install the bolts or the studs

Tighten
Tighten the bolts or the studs to 28 N·m (21 lb ft).




5. For the 7.4L, install the following items:

5.1.	The thermostat into the housing

5.2.	The gasket (If necessary)

5.3.	The coolant outlet

6. Install the bolts or the studs

Tighten
Tighten the studs to 37 N·m (27 lb ft).

7. Refill the coolant to the cooling system. Refer to Cooling System Draining and Filling .
8. Start the engine. Run the engine, with the radiator cap removed, until the radiator upper hose becomes hot (This indicates that the thermostat is open).
9. With the engine idling, add the coolant to the radiator until the coolant level reaches the bottom of the filler neck.



10. Install the radiator cap to the radiator. Make sure that the cap arrows (1) line up with the overflow tube.
11. Inspect the cooling system for leaks.

Engine Coolant Thermostat Replacement Diesel Engines

1. Drain the coolant until the radiator coolant level is below the thermostat. Refer to Cooling System Draining and Filling .
2. Disconnect the radiator inlet hose.



3. Remove the bolt, the stud and the coolant outlet (4).
4. Remove the gaskets (3).
5. Remove the thermostats (2) from the housing (1).
6. Clean the sealing surfaces of the thermostat housing (1) and the coolant outlet (4).

1. Install the thermostats (2) into the housing (1). Replace both thermostats to ensure that the cooling system functions properly.
2. Install the gaskets (3) into position.
3. Install the coolant 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 bolt and the stud.

Tighten
Tighten the bolt and the stud to 42 N·m (31 lb ft).

5. Connect the radiator inlet hose.
6. Refill the coolant into the cooling system. Refer to Cooling System Draining and Filling .
7. Start the engine. Run the engine, with the radiator cap removed, until the upper radiator hose becomes hot (This indicates that the thermostat is open).
8. With the engine idling, add coolant to the radiator until the coolant level reaches the bottom of the filler neck.



9. Install the radiator cap to the radiator. Make sure that the arrows line up with the overflow tube.
10. Inspect the cooling system for leaks.