Overheating Engine

This is a post about a project from the past. A year and a half ago, a College Kid (CK1) I know had some engine overheating troubles with his 96 Subaru Outback. It had overheated on the way home from college on Thanksgiving morning.

We did some web research and made some phone calls and determined that it had all the symptoms of a leaky head gasket. It turns out that this is a classic problem for this particular engine from this time period. Specifically, a leaking head gasket allows combustion gas from the cylinders to pass into the cooling system. Air in the cooling system messes up the flow of coolant and the transfer of heat. Result, engine overheating and a slow stream of air bubbles in the coolant reservoir tank. This car had both of these problems so it seemed conclusive.

The bad news it the cost and time of replacing the head gasket. So, I recruited a second college kid (CK2) to help with the project. CK2 LOVES to work on cars and his winter break started earlier than that of CK1.

So, starting on a Tuesday afternoon in December, we pulled the engine.


Doing this involves a lot of steps and tagging of parts so you can put them back where they belong. It also involves getting greasy and problem solving when things don't come apart as easy as expected. This car started out in Vermont so some corrosion from the road salt made it hard to separate the engine from the transmission.

On removing the head gasket, it had this small area with inadequate sealing and you can see evidence of a bad seal and condensed exhaust gasses in the photos below.



That is all it took to fail. Subaru has redesigned this gasket a couple of times since 1996 due to this problem. The old gasket used a combination of metal and fibrous gasket material (a very standard design) and the new gasket used multiple layers of thick and thin metal with sealing compound applied in a detailed pattern at certain edges. The replacement gaskets looked very, very robust.

So working almost daily in the afternoons, we put it all back together and finished on the Tuesday evening a week after we started. The car has not overheated since so it looks like we succeeded and we saved CK1 about $900 by doing this in my driveway. CK2 and I also had fun and we had no leftover parts. Success.

Rick