1998 Subaru Forrester, 4 cyl. I don't remember the exact specs of the engine.
It's using what seems to be a lot of coolant -- probably 2 qts in a 30 day time span.
There's no leak (I've left cardboard under it overnight to confirm).
When I leave the car running with the radiator cap off, I can see the coolant moving in the radiator, so it doesn't seem like a water pump issue.
We've replaced a lot of the basics in the cooling system recently -- thermostat, some hoses, radiator cap -- in an effort to diagnose the overheating.
It seems like a head gasket leak is the most likely culprit. However, 2 things seem odd to me about this:
- The oil seems normal. There is no evidence of coolant in the oil (it isn't milky looking), and there is no evidence of oil in the coolant.
- The reservoir never drains down. I add coolant to the radiator directly, and the reservoir is always full.
The car doesn't smoke, or smell bad when it runs. It does run rough, and is probably skipping.
The fact that the reservoir never seems to empty (at all), makes me think that I might have a vacuum issue somewhere. But I could be completely crazy, and grasping for something that is not a head gasket. :-)
