Join Date: Apr 2008
Location: Rolla, Missouri
Car Year: 2000
Car Model: Forester
Big bubbles in radiator and overflowing coolant
Specs...2000 Forester, auto, non-turbo, 109,000 miles (owned since 102,000)
Recent maintenance...oil change. Nothing unusual found, no foam, no discoloration.
Problem...When running there is a mild backpressure on the coolant system causing coolant to gently flow into the overflow tank and eventually out the tank vent hole. Putting pressure on the radiator with a guage yielded no decrease in pressure after 5 minutes. If you take the radiator cap off when the engine is running, there wil be big bubbles come up in the radiator, some will pop with a little bit of steam. There's not a lot of bubbles. I've tried smelling the radiator to see if the bubble smell like exhaust, they don't really, and the exhaust doesn't smell like antifreeze or feel wet. The bubble are big and there is no foam in the radiator or catch tank. The temp guage comes up halfway and stays there and the car seems to be running just fine. Even gets 25-26mpg. One other problem is oil on the spark plug boots on the two passenger side cylinders.
I'm planning on having the timing belt, water pump, thermostat replaced soon and am wondering if I'll be staring at a head gasket replacement, too.
How can you tell which side has a head gasket leak?
If I do have to replace a head gasket, is it recommended to do both sides if only one is bad?
I'd appreciate any help as my two local mechanics are in disagreement. One says head gasket, the other, a respected Chevy mechanic who has worked on many of my vehicles, says if you have a head gasket leak it will spurt out of an open radiator.