Hello All, this is my first post on this forum, I bought a 2006 STI yesterday and it has almost 118K Miles on it. It is a clean southern california car. I drove it an hour or so yesterday to bring it home, and when I got here it began to run a little warm (the line above normal) then it would cool off and go back down to the normal position or below. This repeated a few times on cycles as I drove around town, and I thought maybe it was normal for these cars in traffic- because it seemed controlled. Soon enough though it started getting really hot- as I was on the highway I watched it start to quickly head towards the H from normal. I immediately put the car in neutral and turned it off while I coasted to the side of the road. It never made it into the thatched area by the H- brought it to a mechanic today- PO replaced orig thermostat at ~97k miles along with the radiator after similar issues. Said the rad was leaking when it was replaced.. Today the mechanic bled the air from the system and added almost 1/2 gallon of coolant that I probably lost yesterday. There is no oil in the coolant or coolant in the oil. Car does not steam..
Is the thermostat suspect? Any other checks? This is my first Subaru and so far I have met two AAA truck drivers in the last two days.