How Do I Change a Thermostat on a 1998 Subaru Outback?

The thermostat on your Outback acts as a doorman between the radiator and the engine. As the engines temperature rises, the thermostat opens to allow the coolant in the radiator to flow into the engine to cool it down. A defective thermostat often remains stuck shut. This can cause the engine's temperature to rise uncontrollably, creating a risk of immediate and possibly permanent mechanical failure. You can replace the faulty thermostat on your 1998 Subaru Outback right at home. With a few tools, the repair should take you about an hour.

Instructions

1

Raise the hood on your Outback and remove the radiator cap. If you have recently driven the car, wait two full hours to allow the engine and coolant to cool down. Position a coolant drain pan beneath the radiator in line with the drain cock. Turn the drain cock to the right to open it. Allow the coolant to drain completely for 15 to 20 minutes. Close the drain cock securely once the coolant has stopped draining.

2

Apply the Outbacks emergency brake. Raise the car with your hydraulic jack just behind the front drivers side tire. Place a jack stand on the right of the hydraulic jack to help support the car.

3

Slide under the car on the drivers side at the front of the tire. Follow the lower radiator hose over to where it connects to the engine. The thermostat mounts beneath the housing to which the radiator hose is connected.

4

Remove the two bolts holding the thermostat housing cover in position with your socket wrench. Pull the housing cover, with the hose still connected to it, away from its mounting position. Remove the rubber gasket from the inner lip of the housing cover and discard it. Note the position of the thermostat, then pull it straight out of its mounting position.

5

Wipe up any coolant that may have spilled with a shop rag. Wipe the thermostat housing cover and the thermostat mounting area dry.

6

Insert a new rubber gasket into place around the inner lip of the thermostat housing cover. Place the new thermostat back into position just as you removed the old thermostat. The spring on the thermostat should not be visible. If it is, you have installed the thermostat upside down.

7

Place the housing cover back over the thermostat. Thread both of the covers bolts by hand while holding it in position. Tighten each of the bolts with your socket wrench until secure.

8

Remove the jack stand. Lower the car down and remove the hydraulic jack. Refill the radiator with the drain pans coolant and place the radiator cap back on securely. Start the engine and check the repair area over the next 20 minutes for leaks.