I have a 2007 Subaru Forester with just over 200,000 miles on it. It has been throwing P0420 (catalytic converter) for several years. Recently, the ABS, brake, and battery lights started intermittently flashing, before the car would lose power. I replaced the alternator and battery, and then a cracked ignition coil and the spark plugs, which were worn. The lights began to flash again a week ago and it threw P0172 (system rich), so I took it to a different mechanic. He found an oil leak and exhaust leak, and mentioned that the head gasket is likely blown. He says there is "profuse" leaking of oil and coolant in the tailpipe, although the coolant and oil do not appear to be mixing in either compartment.
I was surprised, because the car never overheats and I never see white smoke from the tailpipe. It burns a quart of oil per 1000 miles, but this has been the case for some time. The coolant was noticeably low, however. Obviously it doesn't make sense to rebuild the engine in this old of a car. When I asked him about using K-Seal or some other sealer, he cautioned me that it's "the worst thing you can do," because it can inadvertently seal the coolant passages in the engine. Is this true and is it worth a try if the engine is toast otherwise?
You did pretty well getting 16 years and 200,000 miles out of one of those. Subarus of that vintage are known for head gasket problems. It starts with external leaks and progresses to the point where the failure is internal. They usually fail around 100K miles so they've lasted longer than expected on that engine if it has the original gaskets.
Your mechanic is correct, any so-called "head gasket sealer" you use is as likely to plug up your cooling system as anything else and may not work on the gasket at all. If it did work the effect would only be temporary.
Scotty prefers the Bar's Leaks "Head Gasket Fix" product in the silver bottle if you did want to try something to get a few more miles out of it. You're pretty much at the "nothing to lose" point with that car.
Yeah Subaru had problems with their head gaskets. At least older ones. Yeah I don't think it's worth the repair costs you're gonna pay. And by judging the problems you said the mechanic discovered, you would almost certainly need a rebuild or new engine soon. If you were going to spend that kind of money, you'd be better off getting a Honda or Toyota. Or a Ford...
