Important: During extremely cold weather, -12°C (10°F) or colder, your engine's coolant temperature will decrease quickly when 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 I or II, to maintain the hottest air flow.

1. Drain the coolant. Refer to Cooling System Draining and Filling .
2. Remove the intake plenum. Refer to Intake Plenum Replacement in Engine Mechanical - 3.0L (L81).
3. Remove the intake manifold. Refer to Intake Manifold Replacement in Engine Mechanical - 3.0L (L81).



4. Remove the radiator hose from the inlet housing.

Important: It may be necessary to lift the engine with a floor jack to allow the extension housing to be removed over the radiator.

5. Remove the thermostat extension housing bolt and the extension housing.
6. Remove and discard the O-ring seals.



7. Remove the thermostat with the housing:

7.1.	Remove the bolts.

7.2.	Tilt the rear of the thermostat housing upward.

7.3.	Lift out the housing.

7.4.	Remove and discard the O-ring seal.

8. Use the thermostat extension housing to compress and remove the thermostat from the thermostat housing.

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

1. Check the valve opening temperature.

1.1.	Suspend the thermostat in a pan of water.

1.2.	Gradually heat the water until the thermostat begins to open.

1.3.	Check the water temperature immediately after the thermostat opens.

1.4.	Replace the thermostat if it does not open within specifications.

Specification

•	A new thermostat starts to open at 84-88°C (182-190°F).

•	A used thermostat starts to open at 83-89°C (180-192°F)

2. Inspect the thermostat sealing surfaces for leaks.

1. Install the thermostat with the housing:

1.1.	Install a new O-ring seal.

1.2.	Position the thermostat with the housing.

1.3.	Apply the thread sealant PST 565® to the bolt threads.

Notice: Refer to Fastener Notice in the Preface section.

1.4.	Install the housing bolts.

Tighten
Tighten the bolts to 20 N·m (15 lb ft).

2. Lubricate the extension housing O-rings with coolant.
3. Install the O-rings on the extension housing.




Important: It may be necessary to lift the engine with a floor jack to allow the extension housing to be installed over the radiator.

4. Install the extension housing on the thermostat housing.
5. Install the extension housing bolt.

Tighten
Tighten the thermostat housing bolts to 20 N·m (15 lb ft).




6. Install the radiator hose to the thermostat extension pipe.
7. Install the intake manifold. Refer to Intake Manifold Replacement in Engine Mechanical - 3.0L (L81).
8. Install the intake plenum. Refer to Intake Plenum Replacement in Engine Mechanical - 3.0L (L81).
9. Fill the cooling system. Refer to Cooling System Draining and Filling .