Thermostat Housing: Service and Repair

Thermostat Housing Replacement (L61)

Removal Procedure

Important: During extremely cold weather, -12°C (10°F) or colder, the engine coolant temperature will decrease quickly when the engine is idling with the heater fan on high speed, and cool air may flow from the heater outlets. The fan control switch can be set at a slower speed position, fan speed 1, or fan speed 11 to maintain the hottest air flow.





1. Drain coolant.
2. Disconnect the radiator hose at the thermostat housing. Use Snap-on Tool HOP 10 or 20 or equivalent to remove the hose clamp.





3. Remove the thermostat housing bolts.
4. Remove the thermostat housing and thermostat element.
5. Discard the O-ring.

Notice: The thermostat will not function correctly once it is contacted by oil. If oil is found in the cooling system, it must be flushed and the thermostat's cartridge replaced.

6. Inspect the thermostat components for damage, seat deterioration, etc.

Inspection Procedure

Notice: Use extreme care and do not damage or scratch the machined aluminum surfaces. Leaks will result.





1. In order to verify that if the thermostat valve is opening properly, perform the following test
1.1. Completely submerge the thermostat in the glycol solution. The solution should be 11°C (22°F) above the temperature indicated on the thermostat valve.
1.2. Thoroughly agitate the solution. Under these conditions, the thermostat valve should open.
2. In order to verify that the thermostat valve is closing properly, perform the following test:
2.1. Completely submerge the thermostat in the glycol solution. The solution should be 6°C (10°F) below the temperature indicated on the thermostat valve.
2.2. Thoroughly agitate the solution. Under these conditions, the thermostat valve should close completely.

Installation Procedure





1. Install a new O-ring on the inlet housing.
1.1. Install the thermostat and inlet housing into the thermostat inlet housing.

Notice: Refer to Fastener Notice in Service Precautions.

1.2. Install the retaining bolts.
^ Tighten the bolts to 10 Nm (89 inch lbs.).
1.3. Close the radiator drain plug.






Important: The vehicle must be level when filling with coolant.

2. Fill the cooling system to the FULL COLD line with coolant. Use a 50/50 mixture of DEX-COOL antifreeze and clean water.
3. Run the engine until the upper radiator hose is hot, then add additional coolant, if needed, to bring the level to the FULL COLD line.
4. Install the pressure cap and test for leaks.