1. Drain the coolant until the radiator coolant level is below the thermostats. Refer to Draining and Filling Cooling System .
   Images available only to Customers.
   
   
   Images available only to Customers.
   
   
   
2. On the 4.3L, remove the following items:
   1. The bolts or studs
   2. The coolant outlet
   3. The thermostat from the housing
   4. The gasket (If necessary)
   
   Images available only to Customers.
   
   
   Images available only to Customers.
   
   
   
3. On the 5.0L and the 5.7L, remove the following items:
   1. The bolts or studs
   2. The coolant outlet
   3. The thermostat from the housing
   4. The gasket (If necessary)
   
   Images available only to Customers.
   
   
   Images available only to Customers.
   
   
   
4. On the 7.4L, remove the following items:
   1. The bolts or studs
   2. The coolant outlet
   3. The thermostat from the housing
   4. The gasket (If necessary)
5. Clean the thermostat housing and the cooling outlet sealing surfaces.

Installation Procedure

Images available only to Customers.


Images available only to Customers.



1. For the 4.3L, install the following items:
   1. The thermostat into the housing
   2. The gasket (If necessary)
   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).

   
   Images available only to Customers.
   
   
   Images available only to Customers.
   
   
   
3. For the 5.0L and the 5.7L, install the following items:
   1. The thermostat into the housing
   2. The gasket (If necessary)
   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).

   
   Images available only to Customers.
   
   
   Images available only to Customers.
   
   
   
5. For the 7.4L, install the following items:
   1. The thermostat into the housing
   2. The gasket (If necessary)
   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 Draining and Filling Cooling System .
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.
   Images available only to Customers.
   
   
   Images available only to Customers.
   
   
   
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.