Thermostat: Service and Repair

Removal Procedure





1. Drain the coolant until the radiator coolant level is below the thermostats. Refer to Draining and Filling Cooling System.
2. For the 5.7L only, 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 needed





3. For the 7.4L only, 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 needed
4. Clean the thermostat housing and the cooling outlet sealing surfaces.


Installation Procedure





1. For the 5.7L, install the following items:
1.1. The thermostat into the housing
1.2. The gasket, if needed
1.3. The coolant outlet

Notice: Refer to Fastener Notice in Service Precautions.

2. Install the bolts or the studs
^ Tighten the bolts or the studs to 28 Nm (21 ft. lbs.).





3. For the 7.4L, install the following items:
3.1. The thermostat into the housing
3.2. The gasket, if needed
3.3. The coolant outlet
4. Install the bolts or the studs
^ Tighten the studs to 37 Nm (27 ft. lbs.).





5. Refill the coolant to the cooling system. Refer to Draining and Filling Cooling System.
6. 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.
7. With the engine idling, add the coolant to the radiator until the coolant level reaches the bottom of the filler neck.
8. Install the radiator cap to the radiator. Ensure that the cap arrows line up with the overflow tube.
9. Inspect the cooling system for leaks.