Your 98 Legacy has the DOHC 2.5, which is prone to internal head gasket leaks at the coolant passages. The coolant leaks into the combustion chamber, and is burned up. The tell-tale sign of a head gasket failure on these is a steady stream of bubbles in the coolant reservoir when the engine is running, as well as an overheat. If it is the head gasket, the best practice is to pull the engine, and replace both head gaskets along with head bolts, a new timing belt/idlers/tensioner, water pump, thermostat (HAS to be OEM Subaru), and radiator hoses. Along with that, since many have to come off anyway, you should change the accessory/serpentine belts, the spark plugs/wires (plugs should be NGK, wires OEM), air filter, PCV valve as well as oil/filter change, (basically a tune-up) along with coolant (obviously) and any oil seals (crank/cam seals or rear main seal/oil separator plate). Finally it is also a good idea to have the cylinder heads machined, as the tolerances are very small for aluminum engines. I would recommend OEM parts wherever possible, especially the head gaskets themselves, as well. You can get a head gasket kit as well as other parts from www.subarupartsforyou.com. This is a long, expensive job, but using Subaru's updated head gasket for the DOHC is a true fix.
I have the skill and the equipment to tackle such a job. I've never worked on this type of motor. Thought I might just have to tilt the motor to get at the heads and of course machine them. You say thermostat had to be OEM? Is this loyalty a little over board? Originally i was thinking about 15 hours labor BUT with your recommendations I think I should double it. Now my deliemma this to me is like putting frosting on a bad cake it does have 200,000 on all the internals Should I dig a little deeper and do a rebuild? or maybe pull the motor and put in a remanufactored in? Known anyone who deals in these motors? who writes the best shop manual for this car? Thanks for you insight Are you a Pro?
Not a pro, just a Subaru enthusiast, but thanks. As for the thermostat, if you look around on Subaru forums, everyone says that as well (which is where I learned, and from experience). If you put a standard aftermarket thermostat and an OEM next to each other, they have a very different design and the OEM has a better flow rate. Subarus are very finicky cars, and many aftermarket parts work fine, but certain ones have to be OEM. A lot of people report misfires with aftermarket spark plug wires, which go away with OEM. My opinion is that if you're going to go through all that work, you might as well go all out and use OEM. These parts are known to work well, and are worth the money. If your car has 200k on it, there's no reason you can't get at least another 100k out of it with new head gaskets, as long as the rest of the mechanical components are in good shape. These are very durable engines, and go 300k+ with no issues. Typically these gaskets fail around 100 to 150k, so you got lucky that they lasted this long. Transmissions are also very durable, it is really the body that rusts away long before the mechanics give out. It's your call with that, as I can't see the car. Colorado Component Rebuilders (www.ccrengines.com) is probably the best source for reman engines, although that might be pricey in your case. I don't have much experience with that, so I would seek out a local salvage yard. Most of the time, it isn't necessary to do replace the engine at 200k. If you get the engine out and everything looks good, I would go ahead and replace the head gaskets and be done with it. The thing with the DOHC engine is that it can be done with the engine in the car, but access is terrible and it's much easier to pull the engine. The SOHC in newer models is much easier and different, and you typically don't have to take the engine out. As for the shop manuals, Haynes is very good, but the best way is to get a temporary 3 day subscription to the Subaru Factory Service Manual (techinfo.subaru.com) for $35. The manuals are very detailed, and are broken into small files, so you can download what you need for not very much money. You can probably get all the parts you need from www.subarupartsforyou.com for about $800. I would get everything from there except for the spark plugs, since OEM is overpriced and just reboxed NGK platinums, and obviously the oil and coolant - just get those at your local parts store. I think about it this way, $800 is a lot cheaper than a new car, and if you like the car, it's worth it.
Also, this website is excellent, lots of good info: http://home.comcast.net/~skipnospam/Head_gasket_replacement.html
Thank You for taking the time to educate me. The information you provided will be put to good use. I was thinking Haynes manuals but what I really wanted was the Factory manual and your info on the 3 day sub will come in very handy at a very reasonable price I was researching the cost of the factory manual and it was almost half the cost of the parts, I didn't know about a online version. If I can get another 100K out of the motor with just doing the heads I think I'll do that. after reading up on this motor and clutch I feel in would be in my best interest to Replace it as it's getting weak and I'll be looking at it with the motor out.
thanks again you saved me considerable time and money.
I talked to the local sub. dealer Service manager and he said it didn't matter if I used a after market thermostat but I'll use OEM.