QuestionMy car is now in a shop... suddenly started overheating. Dealer said it was a blown head gasket based on pressure test. Independent mechanic said it passed the pressure test. He replaced the thermostat. Still overheating. Could the radiator be somewhat blocked or plugged up? Any other causes for the problem? Water pump? Why would needle go up on overheating and then come down, and then bounce up again in a few miles?
AnswerOn your era Subaru, we have never seen a bad thermostat. Not a real expensive procedure, but the shop that wants to put a head gasket on is probably right. And you may be also. That engine does not do well if overheated; so, if it got hot, you probably need head gaskets. But, why did it get hot? When the engine is apart getting the gaskets, have the heads checked by a machine shop. Also, replace the water pump, thermostat (just in case), and the timing belt. Also, have the radiator pulled and checked by a shop that can actually measure the flow rate/volume. In our little town, a guy runs water through it and says it "looks" ok. We have to send the radiator about 60 miles away, and about 50% of the time the radiator does not flow anywhere near the rate it should. If your car has a manual trans, the radiator probably isn't as big as of a concern.
Finally, in a very few cases, the block is damaged. The shop needs to look for hairline cracks in the cylinder walls. Very, very, rare. Very. But, possible.
Sorry for the bad news. I guess one more finally, if you don't trust the answer the shop has given you, take the car out of there. I know it wasn't the answer you wanted, but if you aren't comfortable with the answer, get a second opinion, but be prepared for the same bad news.
