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Burnt exaust valve, pull engine?


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I've mentioned on a previous post about a misfire code on cyl 4 that Ive been getting on my 98 outback 2.5. As I stated, I have done just about everything suggested here and elsewhere to solve the problem (new coil pack, plugs, MAF, EGR, EGR solenoid, fuel injector, new vaccum line, cleaned throttle body, and sea foamed (useless). Tommorrow a mechanic buddy is going to check compression again and do a leak down test. My best guess so far is a burnt exaust valve. I can only go by this because of the dollar bill test in which the dollar suck back in. This all leads me to my question.

If it is an exaust valve, my asumption is I will be pulling the head off and going through the motions of rebuiding the motor. Will all this be easier to do if I just pull the engine? or can I access everything from the top and bottom?

 

At this point I dont even know if I can do a job this big since I never done something like this. I am pretty mechanically inclined but it is still pretty intimidating. I do know I cant afford the 3 grand I am guessing it will cost. Can anyone give me some pointers?

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California appears to be a pretty expensive place to live. Next to Japan, maybe the world's most expensive real estate on a fault line. Anyway, I would check on the price of replacing a burnt valve. About $1200 is average for head gasket replacement in most places, and to have one valve replaced is about the same job. I'm guessing, but I'd say $1,500 tops.

Several people with the 2.5L engine have replaced their head gaskets with the engine IN the car. So, I'd say that you could probably do the same.

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Clean the ground wire on the top of the intake. The likelyhood of this being a valve is poor. But if it is heres some advice on the job you are considering:

 

Take the intake manifold off which is 8 bolts/4 per side, the EGR Pipe (17MM flare wrench--spray pen. oil on 24 hrs before attempting to remove), exhaust nuts (3 nuts per side), a couple of hoses on the back of the water pipe that run up to the throttle body, etc. Take your time and step away from the project for 15 min before you try to do the stuff on the back of the intake but otherwise this isn't terribly hard. Gently lifting up on the intake as you go will help. Obviously move the power steering and AC pumps out of the way before you start, they can be laid on the wheel arches if you remove the battery and air cleaner.

 

Then pull the heads, which you can do in the car if you dont have an engine hoist and it wouldn't be that bad but honestly these engines arent terribly hard to pull. then take the heads to a machine shop to have the valves replaced and the seats cut AND LAPPED IN. It would be fairly reasonable to have done and theres pretty much no way you have all the necessary equipment to do the work right on that.

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It might be a good idea to pull the cam cover and check the valve lash.

You may simply have an exhaust valve with zero (or minus zero) clearance.

 

If it's been in this condition for any length of time, though, there's a chance that it may be burned anyway.

 

What was the result of the compression test?

 

Subies usually don't have valve issues.

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I just went through the same experience. Had no compression in two cylinders...mechanic was pretty sure it was burnt valves. Found a 2.2 engine with 70k miles for $500. Cost me $375 for the install and I'm very pleased with the result. Reckon I've save several hundred $$ and have a more reliable engine to boot.

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Well...just got the results on the compression test. Cyl 4 only had 50 psi. Looks like a burnt exaust valve. Suppose that would be a good enough reason for a misfire code.

I guess the next step is to start tearing this bad boy down. I am a little concern about rebuilding a new top end on an engine with 115k on it and not doing the entire engine but at this point I just want to get it fixed as cheap and easily as possible so I can dump it.

I hate to say this here on this message board since everyone has been so nice but I dont think I'll ever buy another subaru. I have had nothing but trouble and have spent over 5 grand fixing this car the 3 years I've owned it. Not to mention that I am still paying the bank for it. Oh well...should have bought that toyota I was going to buy.

 

Thanks all

Brett

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