# Replacing the thermostat on a 2009 Subaru Forester

You need a 10mm socket, a 12mm socket, needle-nose pliers, and about a gallon of coolant. Also a drain pan. Also patience, because the lower radiator hose clamp is in a spot the engineers clearly designed while angry.

Jack up the front, pull the plastic splash guard (six of those push-clip things, they will break, buy extras). Drain the radiator from the petcock on the driver's side, bottom corner. It drains slow. Go make coffee.

The thermostat housing is on the lower left of the engine block, follow the lower radiator hose to where it meets the block, that's it. Two 10mm bolts. Here's the part nobody mentions: the bottom bolt is behind the hose, and you cannot get a normal socket on it. I used a stubby wrench and turned it a sixth of a turn at a time for twenty minutes.

Old thermostat comes out with the O-ring. Note which way the spring faces. Seriously, take a photo, because if you put it in backwards the car overheats and you get to do this whole thing again, which I know because I did.

New one in, spring toward the engine. Torque the bolts to like 7 ft-lbs, they're tiny, don't gorilla them or you'll strip the aluminum. Refill coolant, run the engine with the cap off until the thermostat opens and the level drops, top off, done.

I am not going to tell you to consult a professional. You already decided you weren't going to.
