Where is the thermostat located on a 1990 Subaru Legacy?

The thermostat is located under the engine, driver side very close to the front. There are 2 small bolts you need to remove to take out the housing. Be prepared for falling coolant. :) Good Luck Where the lower radiator hose connects to the engine. Don't bother looking in the Haynes manual. The answers are not there for that engine, only the other models. Once you see it, you will know it. If it is overheating, bleed the system (bleed screw is on top, passenger side under the intake)before you start replacing parts. This is common on these engines because the water pump can draw in air at high RPM's and corrupt the system. If you have a consistent air problem, the water pump may need to be changed. Radiators have been known to collapse after a lot of miles also in the Subaru Legacy models. Check the cooling fan operations and all of the other standard checks before you give up. Many times it is something simple. Just don't let it get so hot that you blow a head gasket. Good luck.