Hello:
I have a 98 Forester L, manual, with 132K miles that has overheated twice, and no one can figure out what the problem is. I thought I would see if anyone here had any ideas.
The first time it overheated, I was travelling on the interstate running about 75. I happened to look down and noticed the temperature gauge moving down. As this gauge has never moved before once the car has reached operating speeds, I kept watching it. It returned to its normal position, but soon thereafter rose quickly up to hot. I immediately pulled over and shut off the car. There was no steam. Once the car had cooled off, coolant was added and the car was fine the rest of the trip (about 20-30 miles). The next morning, it was pressure tested by a general service station, who found no indications of any leaks.
That night the car was driven about 40 miles with no problems - the temperature gauge was at normal position the entire trip. The next morning the coolant level was low again in the radiator. Level was okay in the overflow, but there was an oily-type substance in the overflow. So I took it to a nearby Subaru dealer to be checked out. All they found was a bad radiator cap, which was replaced. The mechanic thought that the oily-looking substance was likely old antifreeze.
The car was driven by my father during the next five days - he put about 500 miles on it. No overheating problems. On the 100-mile drive to return it to me, it overheated again, going from normal to pegged in only a few seconds. Notable I am sure is that it overheated in much the same location as it did before - on the downside of a high-elevation area. It was towed to my usual mechanic, who has not been able to find anything wrong.
I have been suspecting head gasket troubles, but my mechanic tested for exhaust gases yesterday and found none.
One other thing I will mention: it overheated on my first drive beyond just to/from work after having a new clutch and rear main seal installed. I don't think it's related, but at this point I don't know what to think.
Thanks,
N.