I have a 1998 Outback DOHC EJ25D that has 270,000 miles on it. I took it to a shop and had the radiator fluid checked for CO2. Low and behold, CO2 was found. (It has been blowing radiator hose along other head gasket issue indicators) I am planning on tearing the motor down to replace the head gaskets. I am wondering if I should do more to the motor once I have it out. 

 

Would replacing the main bearings be advisable? 

Is there anything else that I need to replace with I have the engine out?

Is it even advisable to replace the head gaskets with this many miles on it?

 

 

Details, I am the third owner. The first owner kept track of every thing that was done with this car. The head gaskets where replaced at around 80k. The second owner was a mechanic who maintained the car fairly. Since having it, I have put 40k on it and replaced several things, rack and pinion, fuel pump, time belt, etc. 

Edited November 24, 201312 yr by Konrad

I wouldn't go into splitting the block. Not cost effective. If the engine has not been consistently overheated, leave it. If it has and you are concerned about the integrity of the rod bearings. Replace the engine.

Do a search for HG and you'll see what to replace.

Off the top of my head.

Use Subaru's turbo HG ending #642. ( You should not have had  to redo HG after 40K!).

If pulling the engine,replace rear separator plate with new style metal one.

retighten screws on the back of the oil pump.

New O ring for oil pump and assorted seals and gaskets.

Download fsm here: https://docs.google.com/folderview?pli=1&id=0B6P6dybMMzg9T25hMEhPdjFVc1k

An accurate 3/8 torque wrench ( the cam bolts are very low #'s)

Good 12 pt 14mm socket

Bag and label your bolts (life will be easier upon install)

Take your time.

Save up on your curse words, you'll have occasion to use a few!

Most of all, have fun.

 

O.

So the original owners HG replacement, which was done at 80K, lasted 190K miles!  I think everyone who has done a HG replacement would be happy with that many miles.

 

While I don't own a 90's DOHC, a number of posters have said that the standard replacement subaru HG's are a good fix.  Note that this only applies to the 2.5 DOHC!  I also think that I have read that the replacement hg's are MLS which you should be able to see at the edges.

 

Maybe some of our mechanics will confirm.

oil preshure check min 10 psi hot at idle if higher engine is ok if lower do bottom end List headgasket x2 seporater plate x1 front crank seal x1 front cam seals x4 must be brown subaru ones valve cover gasket set intake gaskets ex gaskets plugs waterpump/ thremostat subau stat only coged idler or timing belt kitt timing belt. MUST surface heads check block for damage and burning on lower part of fire ring and make shure Cam buckets go back in exact holes they came out of and that they have adaquite clearance to tight will cause missfires

Prep the block surfaces for the head gaskets with a sanding block and some 220/400 wet sand paper.

 

Plus everything that Ivan said with addition to the coolant crossover o-rings. If the small hoses for the throttle body haven't been replaced, might be a good idea to get a hose package from the dealer which will replace the radiator hoses, water pump bypass hose, heater hoses and throttle body bypass hoses. If the radiator cap is aftermarket or has a swollen bottom seal, replace it with an OEM cap.

I whould not sand block to great of chance contaminating engine with sanding dust or particulate I just scrape it very gentaly with razorblade any debrie from cleaning block ends up in oil