Subaru Head Gasket & Clutch Replacement
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Background:

I have a 1997 Subaru Legacy Outback Wagon with the (now infamous) 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...

Tools:

I own the Craftsman 181 Piece Mechanic's Tool Set. It contains a pretty good mix of 1/4", 3/8" & 1/2" drive sockets. Upgrade I have made include trading in the 1/4" & 3/8" ratchets for the new slim head ratchets (which have a 6 degree arc and are totally worth it). I bought a 24" 1/2" drive breaker bar, and 3/8" extension set

After checking a number of sources, I ordered most of the parts from 1stsubaruparts.com. I was very surprised to find some of the dealers in my area actually raise the list price to charge more for their parts. 1stsubaru's list was lower, and the sale price was even lower than that! Don't be afraid to ask for discounts on prices at the dealers. They know they are high, and one offered me 20% off (the same price they give to area mechanics).

Since my clutch was also acting up, I decided to pull the motor and replace that at the same time, as well as do some of the other scheduled maintenance while there was good access to the motor.

If money is an issue, and you want to do the minimum, you could opt for the overhaul gasket set and valve cover and spark plug gaskets and be done for about $200, but this is a very opportune time to replace items such as the timing belt and hoses, since they have to come off anyway.

Parts Notes:

I ordered the Overhaul Gasket Set (a scan of all the parts included is here), which includes the timing belt cover seals, cam seals, rear main seal, water pump and thermostat gaskets, among many many others. It is definitely worth it if you want to renew all of the seals and rubber gaskets in the motor. Strangely, it does not include the Valve Cover or Spark Plug Gaskets. One bad part - all of the parts are loose and not labeled, so you have to spend some time finding what goes where. It is supposed to include the Oil Pump O-ring, but I couldn't positively identify it, so I decided to purchase one separately and install that, to know that the proper one was installed. In my case, I am definitely going to have some of the O-ring and gaskets left over, but it is still a very good value...

It is recommended to replace the Oil Separator Cover (behind the flywheel) if it is plastic. The new one is aluminum.

When pulling off the exhaust manifold, 2 of the studs pulled out, so I replaced them. Similarly, I replaced the clutch fork boot as it crumbled when I tried to take it out, and one of the timing belt idlers seemed dry, so it was replaced.

Valve shims are a royal pain in the ass. Many dealers do not stock them. Find a local dealer who does, and buy from them. No matter how careful you are, some of the clearances will not work out correctly, and you will have to exchange some of them. This is easiest at a local dealer, rather than having to wait for parts to be shipped. Be prepared for them to be out of stock of a lot of them, so have some alternates (a size up or down) in mind. The dealer I was dealing with eventually handed me the bin of shims and just told me to find the ones I wanted.

One final note: check the condition of parts as you are tearing the motor apart, rather than waiting until you are putting things back together. I didn't find the bad idler pulley until I was ready to put the belt back on, and was sent scrambling to find one from the dealer.

Machine Shops:

A very important step before you get started is to find a good machine shop. Sometimes this can be more difficult that flipping through the phonebook. After finding one that was just getting started, I was talking to my neighbor who happened to know of another one, who he highly recommended. He rented space in a regular auto repair shop, and his business was largely word-of-mouth. He did a lot of fleet work and I felt very comfortable with his experience and expertise.

You can check the heads for warpage using a straightedge and feeler gauges yourself, but given the tolerances (0.002" for head warpage), this may be better left to the pros with good equipment. While the machinist had the heads, I had him press in the new valve oil seals with new keepers (included in the gasket set). He also machined the flywheel and pressed in the new pilot bearing. He had the heads and flywheel for about 3 business days; he probably could have turned them around quicker if I could have given him advance notice, but I didn't find him until the last minute. The total for all the work was $70.

Technical References:

For documentation to help change the head gasket, there are a few options. Both Haynes and Chilton have produced repair manuals for the Legacy. I own the Haynes, and it is pretty through, giving good detail and many of the same illustrations as were in Subaru's Shop Manual. Chilton's manuals are somewhat notorious for having poor information, so I steered clear of it. Due to the complexity of this repair, I decided to download a copy of Subaru's Shop Manual (available here). A 72 hour subscription costs $20, and is well worth it. But beware: the manual is broken into individual subsections, with each containing multiple PDF files. Downloading the entire manual took about 5 hours on a DSL line, with approximately 800 files and around 225 MB. You will have to cut and paste the section title in for the file name, otherwise you will end up with a lot of files with names like w98735490.pdf, which are very difficult to navigate. It is also easiest to set up a directory structure on your computer like the menu system that the website uses.

The Shop Manual provided excellent detail, showing the locations of every connector and bolt to remove, and it gives torque and inspection specifications for all parts. The following is a list of all of the sections I printed and used for this project:

Timeline:

Additional Resources:

Below are listed some additional resources for information, parts or forums to ask questions.

Disclaimer: This site has been created to be a reference to the Subaru community. Perform repairs at your own risk!