I replaced the engine in a 96 outback for a friend of mine and now he has a weird issue. If he drives the car it runs fine, but if he lets it idle for any length of time the temperature goes up. If he gets in the car and just revs up the motor, the temp will come right down. The cooling fans are coming on too. The temp never wavers while he is driving, only while he is idling. He tells me that the coolant level is just fine and I am thinking that he may have a stopped up radiator or a bad T stat.

 

Any thoughts are much appreciated. I don't want him to overheat the car and have to do a full reseal.

 

Thanks Guys

I'd suggest replacing the t-stat. It sounds like the current t-stat may be a non-Subaru t-stat. The Subaru t-stats are different and make a difference in how the cooling system works.

 

I'd start there, and if that doesn't help, check the radiator.

Same thought, replace the t-stat. Might need to boil out the radiator too.