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EA82 - no compression in one cylinder


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32 replies to this topic

#1 jasonkaye

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Posted 14 August 2017 - 05:26 AM

Hi all,

 

My 1991 4WD Loyale stationwagon has been burning some oil for years, which doesn't appear to be a problem so long as I keep the oil level topped off. Recently, things have gotten worse. Now, the car is burning a lot of oil (clouds of smoke out of the exhaust when the engine is first started.) After the engine warms up, the engine appears to be burning less oil, but still burning oil.

 

Yesterday I did a compression test. Cylinders #1, #2, and #4 show about 140psi in a dry test and 160psi in a wet test. Cylinder #3, however, showed zero compression in both dry and wet tests. As far as I understand, this means either worn piston rings or an open valve.

 

Two questions:

 

1. Do you have suggestions on next diagnostic steps?

 

2. As this is my daily driver, is it safe to continue to drive this vehicle in its current condition? Or, should I park the thing until it's fixed?

 

Thanks!

 

Jason



#2 idosubaru

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Posted 14 August 2017 - 06:00 AM

If it's a valve issue then the risk of dropping a valve into the cylinder? If it's just a valve stem seal issue that shouldn't be the case.

oil or burning byproducts on the O2 sensor and catalytic converter, though that shouldn't cause drivability issues. excessive blow by can make its way up into the PCV and intake manifold.

lack of power will increase work load of each cylinder by 8%. risk compromising oil flow if level isn't maintained well.

will the imbalance of having just one piston turn the crank hurt, probably not?

#3 john in KY

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Posted 14 August 2017 - 11:20 AM

Compressed air may be able to pinpoint the problem.

Apply air to the cylinder with the valves in the closed position. If you hear compressed air escaping through the exhaust, should indicate a vale problem. 



#4 Gloyale

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Posted 14 August 2017 - 11:22 AM

you could pull valve covers and look for excessive clearance on a valve, might have a stuck one.

 

otherwise, I would say you've got a blown ring land/ring.

 

replace the piston.



#5 wagons

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Posted 14 August 2017 - 05:07 PM

Do it the easy way. Put 1-2 tablespoons of oil in the spark plug hole for cylinder not reading. Do compression test on that cylinder immediately. If compression rises you have bad rings, piston to wall gaps ECT and that cylinder needs repaired. Next if doesnt go up, do a leak down test and listen closely for air. It could be a head gasket, could be valves, could be timing belt jumped and not closing valves.

#6 Gloyale

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Posted 14 August 2017 - 05:40 PM

wet test wont really work on flat engine.....oil goes to the bottom only, top of rings stay dry.

 

t-belt would likely have an effect on both cyl not one.

 

leakdown will reveal whether valves or rings



#7 Dee2

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Posted 14 August 2017 - 08:00 PM

Put a vacuum gauge on it and see what the readings are.

 

http://www.secondcha.../public/186.cfm



#8 ferp420

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Posted 15 August 2017 - 09:45 AM

If you drive on 3 cyclinders tbe dead cyclinder will eat its rod bearings over time if it was a valve issue like not opening then it would still have compresion there might be something stuck in the valve holding it open but most.likely its your rings the #3 cyclinder gets its oil last and can heat up faster than the other ones and its likely that piston got hot and siezed in its boar breaking or colapsing the rings it happen to vw engines all the time if thats the case the cylinder boar might be damaged the right thing to do is toss the motor or boar it out however you.could cheap out and just hone the cyclinder and replace the rings and maybe the piston im sure some one has one laying around not the end of the world but its alot of labor i say park it or find a new motor and run that one till it wont lol



#9 wagons

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Posted 15 August 2017 - 07:34 PM

I have done oil in cylinders on countless subarus vws and even a couple Porsche engines, they all were spot on for the dead cylinders. Leakdown test is the best way, I agree but oil test is simpler. Just trying to help him out.

#10 Gloyale

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Posted 15 August 2017 - 07:48 PM

I have done oil in cylinders on countless subarus vws and even a couple Porsche engines, they all were spot on for the dead cylinders. Leakdown test is the best way, I agree but oil test is simpler. Just trying to help him out.

 

You may have just been seeing the rise in compression from adding a volume of non-compressable fluid to the cylinder.  This effectively shrinks the chamber volume, bumping compression ratio.

 

careful...too much oil for a wet test can hydro lock the cylinder, just like sucking water.



#11 jasonkaye

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Posted 18 August 2017 - 09:51 AM

I just took off the valve cover on what I think is the problematic side of the engine (cylinders #3 and #1, the passenger's side.) Attached are some photos. I don't quite know what to look for, but my untrained eye doesn't see anything obviously wrong.

 

Rear of the engine (cylinder #3) is to the left in the photo; front of the engine (cylinder #1) is to the right in the photo.

 

IMG_20170818_102925129.jpg

 

Primary view of one valve spring, rocker arm, and cam lobe for cylinder #3, below...

 

IMG_20170818_103052934.jpg

 

Primary view of the other valve spring, rocker arm, and cam lobe for Cylinder #3, below...

 

IMG_20170818_103009615.jpg

 

Do you see anything of note in the photos?

 

I will follow Dee2's suggestion to hook up a vacuum gauge this afternoon.

 

 



#12 jasonkaye

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Posted 18 August 2017 - 01:27 PM

Just performed a vacuum test, following Dee2's suggestion. The needle on the vacuum gauge fluctuated rapidly between 15 and 18 in-Hg. As I revved the engine, the vacuum increased but maintained a rapid fluctuation over a range of 4 in-Hg. From what I've read, these results indicate worn valve guides.

 

So, do we consider this a confirmed diagnosis, or are there more tests to do?



#13 Gloyale

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Posted 18 August 2017 - 01:54 PM

Just performed a vacuum test, following Dee2's suggestion. The needle on the vacuum gauge fluctuated rapidly between 15 and 18 in-Hg. As I revved the engine, the vacuum increased but maintained a rapid fluctuation over a range of 4 in-Hg. From what I've read, these results indicate worn valve guides.

 

So, do we consider this a confirmed diagnosis, or are there more tests to do?

worn valve guides would not cause a no compression result.  I mean they might be worn......but that's not the problem.....not part of the combustion chamber.  They seal the valve stem, not the chamber.

 

you need to check that the valves are closed....which they look to be from pics but you'd have to measure to tell for sure.

 

But everything in my mind is saying cracked piston/blown ring land.



#14 Dee2

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Posted 18 August 2017 - 03:16 PM

Sounds like it could be a valve problem.  Scenarios 5,6,7,8 on the interactive chart all have similar readouts on the vacuum gauge.  All indicate a valve problem.  Subtle differences distinguish types of valve problems.



#15 jasonkaye

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Posted 18 August 2017 - 03:24 PM

Gloyale,

 

What do I measure to determine that the valves are closing properly?



#16 Gloyale

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Posted 18 August 2017 - 10:05 PM

basically are the cam followers riding on the lobes or is there slop when on the 'closed' portion of the cam



#17 scoobiedubie

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Posted 21 August 2017 - 05:07 PM

Could be a horrendous crack between the valve openings that has allowed a breach of the compressed gasses.  A bad piston ring would make all kinds of noise.  A bad cylinder head gasket would pump hot gases into the coolant system ending in a boil over.  Subaru heads love to crack between the valves.  Simple fix is another cylinder head with a valve job.



#18 Subaru Scott

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Posted 21 August 2017 - 09:57 PM

Could be a horrendous crack between the valve openings that has allowed a breach of the compressed gasses.  A bad piston ring would make all kinds of noise.  A bad cylinder head gasket would pump hot gases into the coolant system ending in a boil over.  Subaru heads love to crack between the valves.  Simple fix is another cylinder head with a valve job.

 

Bad piston rings do not make noise. Sorry, no.



#19 Gloyale

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Posted 22 August 2017 - 01:02 PM

Bad piston rings do not make noise. Sorry, no.

 

thank you.  I was gonna call this out too but trying to let more stuff go.

 

 

The OP just needs to do a leakdown.......listen for the wooshing air and that will tell where it's going.



#20 jasonkaye

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Posted 27 August 2017 - 03:04 PM

Thanks all. Well, I ended up taking the car to a shop that says it's leaky valves. I'm waiting for a cost estimate, though I'm leaning heavily toward doing the job myself. I have a set of heads from my previous Loyale that I'll send to a machine shop to do a valve job.

 

Since I'll be diving so deep into the engine anyway, is it worth it to remove the pistons and check the rings? Seems like I should check while I'm in there...



#21 Gloyale

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Posted 27 August 2017 - 03:28 PM

Since I'll be diving so deep into the engine anyway, is it worth it to remove the pistons and check the rings? Seems like I should check while I'm in there...

 

yes.

 

if nothing else it will give you a chance to clean the oil rings of all the burnt gunk and get them unstuck and scraping cylinder walls of oil properly.



#22 jasonkaye

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Posted 31 August 2017 - 07:23 PM

Alrighty folks...

 

I have an old set of EA82 heads that I brought to a machine shop to get cleaned up and looked at. I'm awaiting their response. but I'm preparing to do a head swap in the coming week.

 

Since you all have been so helpful to me with this and other issues over the years, I'm going to give back and attempt to do a full write-up with photos of my teardown and rebuild. It might be of use to someone on here one day.

 

I'll start a new thread for that, and I'll add the link here.

 

Jason



#23 jasonkaye

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Posted 04 September 2017 - 10:04 AM

I just finished tearing down the engine enough to remove the cylinder heads. Check out the photo below of the exhaust valve for cylinder #3 (to the right in the photo.) The valve has got that chunk missing, and both valves are caked with carbonized gunk.

 

right-cylinder-head.jpg

 

Well, that explains the systems: no compression on cylinder #3, burning oil out the exhaust, lack of power.

 

The #3 piston doesn't appear to have damage to it's surface.

 

I have another set of cylinder heads that are being serviced by a shop. Before I put those on though, I'd like to get to the bottom of why the valve broke in the first place. Any thoughts?

 

Jason


Edited by jasonkaye, 04 September 2017 - 10:05 AM.


#24 DaveT

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Posted 04 September 2017 - 10:44 AM

I've never seen that.  Put it in the rare category.



#25 Len Dawg

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Posted 04 September 2017 - 10:48 AM

Wow!I would speculate to say looking at the other valves the one intake looks really white like perhaps a lean condition and it got really hot? And or piece of the spark plug came off at one time and got smacked and weakened it..?

I had something gouge my camshaft like a ball bearing but it still works...

Attached Files


Edited by Len Dawg, 04 September 2017 - 10:52 AM.





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