How is oil getting into cylinder 4? (SPOILER - 10/20/2014 Conclusion - piston blow-by)
Car is at 85 k miles and has intake side PCV delete and an OCC.
The trouble was that it was consuming oil. Lots of oil smoke in the exhaust. Oil was also present in the engine compartment especially on the right (dipstick) side.
I installed a new cylinder head cover which did not help
Leak-down test showed cylinder 4 very bad. Altered oil refill cap vacuum test showed varying and too high pressure. I noted movement of the dipstick from the crankcase pressure.
Removed the cylinder head and found oil coating the exhaust manifold passage from cylinder 4. No oil along the entire air intake path. The valves all looked closed tight.
The head had the usual caking of carbon in the intake side of the manifold. My local machine shop cleaned the head up. They found nothing wrong. The valves in all cylinders showed no problems with the guides or seals.
I see no problem with the head gasket. There is no apparent problem with the piston or the rings. I poured some marvel mystery oil into the cylinder and none had leaked out a day later. I don't know what other test I can perform on the piston/cylinder without disassembling the lower part of the engine.
How is oil getting into cylinder 4?

PudgyMech

 

Have you run a tune? When the stock internals run a aggressive tune, aka stage 3, they can fail...
I only ask cause n14 motors that have run high boost can have the pistion skirts fail, and the rings cannot work cause they are no longer held in position.......results in high blow by, oil use, and result is, you need a motor cause it skuffs the cylinder walks.
If the motor was together, a leakdown test would be used to check for this...
This is just a guess...but a few years ago when the handheld tuners were common, there was a few....common thread was high blowby, sometimes blowing the dipstick out, etc...
Maybe you are lucky and only have a ring failure....but if the head is OK....must be the pistions/rings...

 

Everything but the OCC is stock on Pudgy. The leak-down test on that cylinder failed; that's why I was sure there would be problems in the head.

Looks like a complete tear down or a crate N14.

 

Don't take my word on it...just a guess...get more opinions!!

 

Have you done wet and dry compression tests? That would tell you if Cylinder #4 has bad rings. Marvel Mystery Oil sitting on top of the pistons will not tell you if the rings are bad, it's too thick. The only way you can pressurize the crankcase is with poorly sealing piston rings and/or a bad PCV valve.

Did you block off the PCV line to the throttle body when you installed the Oil Catch Can? If you did, try removing the block off and see if the problem goes away. That would tell you if your new PCV valve is malfunctioning, the PCV connection to the turbocharger may not be opening under pressure as it should.

Dave

 

you should be able to get a vacuum on the crank case through the turbo inlet if you are getting positive pressure then there is huge blow by or failed pcv. remember rings are really about dynamic sealing and need to seal with the engine running. try taping a bit of cardboard over about 2/3 of the air filter, warm the engine up, at idle remove the oil filter cap place it upside down on the opening it should just bounce around not fly off next place your hand over the opening you should feel a slight vacuum try having an assistant rev to 2000 rpm you should feel vacuum increase, if you feel increasing pressure instead of vacuum its bad piston/rings. I tried asking about rebuilt crate engines but was not given any info on what was done to the engines so rebuilt myself if they don't answer questions about rebuilt and offer a bit of warranty I would go new or build myself.

 

Attached are shots of the sides of the piston. Does the patterns of carbon deposits demonstrate blow-by? Should there be carbon below the
oil ring?

This is the first piston I've ever removed for exam. I will be measuring it and the cylinder bore tomorrow.

PudgyMech

 

Looks like blow-by to me, is the black carbon in the ring groove hard or somewhat soft? I see the black carbon in the two upper ring groves, I also see the small scrape marks well blow the oil ring.

 

Patient - 08 Alabama MCS with 85k miles burning oil
Diagnosis - Ring damage from abrasive particles from carbon deposits. The direct injection carbon deposits in the intake and on the top of the piston shed small particles that wore out the rings prematurely causing blow-by and oil consumption.
Treatment - Complete rebuild or crate engine.
The core on the crate engine is $500.
Any idea if the market value of the engine as is (in need of a complete rebuild) or parted out might be higher than $500?

PudgyMech

NOTE:I found that the N14 #4 piston can be removed without taking off the oil pump. Four is the only cylinder where the pump does not block access to the connecting rod bolts.

 

That brings up one option....
Re-ring that ONE bad pistion...maybe use some old school techniques (the old ball style cylinder smoother thinngy...forget the name) to clean up the #4 bore....
Not ideal....but if the other cylindars were OK...might get it running OK for quite a bit longer....not sure if your oil burning/leaking damaged the turbo+ cat.....but one inexpensive option to consider if you might swap the motor (or the entire car) later.....
I remember ahortly after the n14 motor was phased out, the price dropped for a few months...not sure it it was a true sale, but guessing if it will happen with the n18 now that the gen3 has reduced engine need....

 

This is a potential "band aid" solution, don't do it, the odds are it will be a total waste of money.

I doubt that this piston is the outlier, I bet the rest are not far behind, with rings that are near the point of failure. As a long time mechanic I have never seen a piston with deposits this heavy on a sub 300k mile engine. The varnish deposits alone indicates oil that was used far past its condemnation point.

I would like to see some pics of the cylinder head deck (cam side) because I suspect that the remainder of your engine is as heavily fouled as the pistons.

As far as a crate engine vs rebuild: If the bores and pistons are in good enough condition for a deglaze and re-ring do that. If, on the other hand, they worn/damaged to the point that a bore and new pistons are required then the odds are you are better off with the crate engine - particularly if you intend to keep the car for another 87K. Another way of looking at this is if the cost of a rebuild/repair will cost more than 50% of a crate engine , get the crate engine - it is likely to more reliable and less hassle overall.

Given the challenges you had in diagnosing this issue, I suggest you not attempt to do the re-ring job yourself. Not trying to be a hard *** here, but since it appears you have not done much (if any) engine work, it can be a very expensive education for a first timer.

Unless you have already made the decision to get the crate engine, I suggest you is the following:
1) complete the dis-assembly of the engine
2) Take the block and pistons to a shop and have the bores and the pistons evaluated.
3) If the bores and pistons are good enough for a re-ring with old pistons go that route.
4) If the rest of the engine is as badly fouled as I suspect it is, get a vacuum pump ASAP!

Otherwise get the crate engine.

Good luck!

Peter

 

Thanks Peter. The block is following the head to the machine shop as soon as I pull it out.
Is it possible to take the engine out without taking the transmission with it?
I have stripped everything but the water pump off the 'front' of the engine. THere seems to be about an inch and a half of room for pulling the engine away from the transmission. I have the instructions to remove just the transmission but not for just the engine.
PudgyMech

 

Replied to the above Q here:
https://www.northamericanmotoring.co...ly-engine.html

w.r.t. new vs. rebuild - I went through the same quandary and ended up buying a new BMW/MINI rebuild assembly for $3364. More here:
https://www.northamericanmotoring.co...ck-needed.html

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