The thermostat mounted on the engine of a 1999 Subaru Outback controls the amount of coolant flowing in and out of the engine. When the thermostat fails, it will either allow coolant to endlessly circulate between the engine and radiator, or it will not all any coolant to circulate at all. Either condition can cause the engine to overheat, and when that happens the engine can get seriously damaged. To fix the problem you have to replace the thermostat.
Instructions
- 1
Allow the engine to cool for several hours before you drain the coolant. Lift up the front end of the Subaru Outback with the jack and put it down on a set of jack stands. Put the drain pan below the petcock at the base of the radiator. Open the petcock and allow the coolant to drain into the pan.
2Locate the thermostat housing on the driver's side of the engine near the radiator. Remove the hose clamp securing the radiator hose to the thermostat housing using the flathead screwdriver. Pull off the radiator hose. Unbolt the thermostat housing from the engine using the 3/8-inch ratchet, extension and sockets. Pull the housing away from the engine and note the orientation of the thermostat. Remove the thermostat and gasket.
3Scrape both surfaces of the thermostat housing and engine using the gasket scraper. Install the replacement thermostat and gasket in the same orientation as the original by bolting the thermostat housing to the engine with the 3/8-inch ratchet, extension and sockets. Reinstall the radiator hose to the housing using the flathead screwdriver.
4Open the radiator cap. Fill the radiator with the pre-diluted coolant then reinstall the cap. Lower the Outback off the jack stands with the jack. Start the engine and turn the climate controls to high and full heat. Allow the engine to run for 10 minutes, then turn off the engine and let it sit for an hour. Open the radiator cap again and top off with coolant.
