"Background:

1997 Subaru Legacy Outback Wagon with the 2.5L EJ25 engine. Around 72,000 miles the car overheated. The night prior, I had just driven 200 miles home. That morning, I started the car, and made it about 2 miles from home, when I noticed the temperature gauge starting to rise above its normal range. I quickly pulled over as the gauge was just getting to the lower of the "hot" marks and immediately shut off the engine. I popped the hood and checked that the fans were running. I could hear the system boiling over and pushing fluid into the expansion tank. After a few minutes, I turned the heater on full and started the car. The temperature gauge returned to its normal position. I thought that the thermostat had stuck, and replaced it along with a coolant change. After thoroughly burping the system, I found that after longer drives (20 miles or more), the coolant would be pushed out to the expansion tank, and then bubbles would start coming from the hose connecting it to the radiator. After the car cooled, it would not pull coolant back into the radiator. This is a pretty strong indicator that the head gasket is blown.

For confirmation, I tried testing the compression of the cylinders. The readings for each cylinder all ranged between 200-210 PSI. After consulting with the Ultimate Subaru Message Board, some readers mentioned that the way this head gasket fails, it is often possible to not have the leak show up on compression tests. For confirmation, you can test the coolant for hydrocarbons (exhaust gasses in the coolant), but seeing the bubbles in the expansion tank was proof enough, and the test runs around $40-50.

Being unemployed at the time, and getting estimates ranging from $800 to replace just the head gaskets to over $2500, and needing to do a clutch as well, I decided to do it myself, take lots of pictures, and write this article to help all those who might find themselves in similar situations. My mechanical background is somewhat limited - I've done oil changes, brakes, belts, and even timing belts on Civics (though they are pretty easy), but this is definitely the most I have tried..."