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EJ25 DOHC engine overhaul questions


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#1 gcronau

gcronau

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Posted 03 June 2005 - 05:45 AM

Long time reader, first time poster here, etc, etc.

I have a 97 Outback with a phase I EJ25 2.5L DOHC engine. In fact, the OB is identical to the one on Skip's Subaru Repair Page(<waves> Thanks for the webpage Skip!).

It has 165K miles on it and came from a family that believed in the "change the oil when it breaks down" school of maintenence. It's amazing that it survived this long. The head gaskets have, of course, blown. I decided to tear the engine all the way down. In addition to the bad HG's, I suspected a rod-knock. In the process I found a 1 bad rod bearing, badly distored crankcase and oil pump o-rings, piston oil rings jammed in their grooves from crud, and a dark "golden" appearance all over the inside of the blocks and heads from oil varnish. All the pistons have a very thick layer of varnish on their sides and skirts, and a thick layer of carbon on their tops. The #3 con-rod journal on the crank is scored and may need to be machined, and coolant leaked back into and pooled in the bottom of the #1 cylinder (actually the wall of the cylinder depending on how you look at it.) It left a rusted/pitted patch about 2.5" long by about 3/4" wide on the cylinder wall. What a mess....

I actually have a bunch of questions I want to ask about this engine and see what the group concensus is on various repairs, but I'll just start off with a couple of simple ones: (Yes, I've already RTFF, but I may not have been using the right search keywords to find what I'm looking for.)

1.) I want to take the valves off the heads and inspect them too while I'm at it. I've done everything else and I might as well check them too. The valve springs are recessed down inside the heads and my old spring compressor won't work. Short of popping for a Subaru ST($$$$$), can someone reccomend a *specific* compressor(brand/model#) that either works with these heads, or can be kludged to work with these heads.

2.) Any suggestions on cleaning fluids to get the baked on varnish/crud off the pistons and camshaft areas of the heads? I've tried soaking in gasoline and laquer thinner with only moderate success. I'm hoping for something better than "elbow grease and a toothbrush". :-)

3.) Both ends of the crank have a pair of bright skiny grooves worn into them from the oil seals. Is this a problem? Do I need the crank ends turned and oversized seals? Or will just a little polishing with an oil stone and 600 or 1000 grit be sufficient?

4.) 3 of the con-rod bearings had moderate wear on their thrust halves. #1 was still all grey/silver, and #2 and #4 had small patches of red copper showing through. All 3 associated crank journals are smooth and mirror bright. Bearing #3 has a *large* area of bright red showing through, at least 40% of the thrust side is red. It's also worn unevenly, with most of the red to one side of the oil hole. That side also has fine scoring on both bearing halves and the crank journal. Running my fingernail across feels like the surface of a very shallow phonograph record. I'm concerned about the uneven damage. Could this be a bent crank, or is it more likely I just had crud come up the oil passage and lodge/block at the bearing?

5.) I've talked to 2 machine shops so far and they both want to re-machine all 4 crank journals, not just the 1 bad one, and then use undersize crank bearings on all journals. Is this reasonable or overkill? They also quoted around $120 for machining all 4 journals. Is this a reasonable price for such a job?

6.) I've checked the heads and they are surprisingly flat. I've cleaned all the carbon and crud off the combustion or block mating surface, but I'm bothered by something else. The old gaskets appear to have impressed a pair of light concentric grooves into the heads. There is also what *might* be very light blow-by damage on the head surface at the bottom between the combustion chamber and the water passage. (By "bottom" I mean the part of the head that would be closest to the road when the engine is installed in the car. The part of the face that is towards the exhaust ports.) In fact, when you run a fingernail over them, the grooves on the face also feel deeper at the bottom of the face than they do at the top. It doesn't look to me to be a good surface for the new HG's to seal against, so I'm planning to have the heads machined down a little. Does this seem reasonable or overkill?

7.) My biggest fear is the rusted spot on the #1 cylinder wall. If I can't hone the damage off, I'll need to have that cylinder re-bored for an oversize piston. Problem is, I can't do just one, they all have to be re-bored or the engine will be out of balance. That means 4 new oversized pistons, a new set of rings, and the cost of re-boring 4 cylinders. A cost I'd really like to avoid. Fortunately, #1 is the smaller "B" grade piston. My current plan is just to hone the cylinder a little and see what it looks like after I've taken off maybe .0005" to .001". I could then put in a new "A" grade-size piston. Any opinions on the long-term effects of some minor cylinder wall blow-by(if I can't hone off all the damage) or piston slap(if I hone off all the damage, but end up opening up the piston/cylinder wall clearance close to, or even wider than, the .002" spec)?

8.) When I rebuilt VW engines many-year-go-by,. we used Lubriplate "AERO" white lithium grease as an assembly lubricant for all the main/con-rod/piston/cam bearings. Any opinions on continuing to use it? Or should I just use engine oil as the Suby tech manual suggests?

Whew! Ok, I guess I lied. It ended up being more than just a couple of questions. :-) I've been using a digital camera to document the engine extraction and dismantlement. If it helps, I can send pics of the various bearings, heads, cylinders, etc.

Thanks for any help or insights.




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