i have a 99 outback wagon 2.5L, and it overheats..
it started a couple of months ago. i had driven for an hour at hight speeds(70 mph), and when i stopped( for about 5 min)to make a u-turn, the temp rose to 4/5 hot.. as soon as i moved forward with a little gas, it dropped like a rock to normal.. nothing more for 2 months, temps stayed perfect..
about 2 weeks ago it happened again after a long trip at high speeeds, i slowed down and the temp went up...stayed kind of hot(depending on how fast i was going) for about 15 minutes as i made my way to the house. again, it heated after i had slowed down and was entering the city...this time i saw what i thought must have been oil in the overflow, but my mechanic said it was just dirt and crud from the sytem.. two mwchanics have done compression tests and tell me they find no head leaks...
now, after having repaced the water pump, thermostat, pulled and cleaned the radiator, it will overheat after 30-40 minutes of driving (enough time to get good and warm, but ONLY when i stop. if i put it into neutral and rev it up, temp will fall immediately back to normal.
I drove it fast the other day for 1 1/2 hours, cool as can be until i stopped, temp shot up, i gave it gas(in neutral) and temp drops. there are a lot of bubbles (and frothing after a while) flowing into the overflow tank though... up till now i havent really been losing much or any coolant either...
i am about to get the head gaskets redone just because i have tried everything else....
what can it be?