I recently bought this car from a neighbor, who warned me that it overheated, but I had bled the system and the car ran fine. Thinking the problem was dealt with I redid two bearings and all the struts, about $500 for everything, but now the overheating is back.

The car runs really well with no problems for about 5 miles, then all of the sudden, the temperature will slam up to the red like the thermostat closes. I've done my research and everything points to a blown head gasket, which would make sense, but the engine was recently replaced and none of the other signs are showing. There are no bubbles in the reservoir, no corrosion on the radiator cap, no excessive white smoke, the oil is perfect, and there is no extreme loss of coolant.

Is there any other reason that the thermostat would randomly close like this?

  • 1
    When the car "ran fine" after you bled the cooling system, were you able to drive long distances with normal temperatures? Did you try bleeding it again? It seems like an obvious thing to look at would be the condition/operation of the thermostat. Have you checked that?
    – dlu
    Commented Nov 27, 2016 at 8:59

1 Answer 1


Subarus are very picky about thermostats; you need the OEM one. I'd start there, and then bleed the system; again, Subaru's are picky, and there is a bleed procedure to follow.

If both of those are done correctly and the problem persists, I'd still be looking at the head gaskets - especially if I didn't know who did them. If a JDM (Japanese Domestic Market) engine was dropped in cheaply, they have been known to come with head gaskets already blown, for your convenience. Have a sniff of the coolant reservoir; if it smells of exhaust gas (on up to 1999 models), that's lots of money evaporating.

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