Stuck piston rings causing oil consumption

[kevinye77137]

I read some forums saying sticky rings were the cause of their oil consumption ( 1qt every 300 miles) in our platform. After freeing them with piston soaking and other shit their oil level has not moved a drop. Whoever tore down thier engine and looked at their piston rings and grooves, are there carbon deposits sticking/ clogging rings?

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[jmcS4]

Not on my old block. You may have scored walls. Or your valve seals & guides are shot. Pull your intake and see if oil is pooling on the valves.

Also use a borescope to check your walls and do a compression test


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[VinnysS4]

I'm getting ready for a tear down. I'll post pictures up on my build log

[kevinye77137]

Not on my old block. You may have scored walls. Or your valve seals & guides are shot. Pull your intake and see if oil is pooling on the valves.

Also use a borescope to check your walls and do a compression test


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I did my valve seals already. Nothing changed. Didn't do compression check or scope the walls yet. But i know my pistons are really carbonized leading to me thinking piston rings are stuck. Going to use marvel mystery oil and clean it out. If that doesn't work then for sure cylinder walls

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[jmcS4]

Won't hurt to try. Did you just do seals or guides as well?


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[kevinye77137]

Just seals. Since stem guides are not included in the jhm built heads I'm guessing it's not a common failure

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[aroderick56]

jhm replaces valve guides in their heads

they dont exactly fail, more just get worn out. I replaced all 40 in my heads because they were so worn

in comparison to other valve guides, these are really short and will not last like guides in, for example, an LS head

[neilpaku]

Hi Kevin, yes my wife's car's engine had this problem, although most of the oil went out the valve guides.

[emilio]

there are numerous ways to lose oil through the cylinder, and i don't think the matter is settled with our engine. this thread is worth revisiting: http://www.audizine.com/forum/showth...V8-consume-oil

neil, how gunky were the intake runners relative to the last time they were cleaned? i figure that could be a differentiator between valve seal leaks and piston ring issues: ring problems could raise crankcase pressure via blow-by or burning oil, triggering intake recirculation that slowly sludges the runners. valve leaks would just burn up in the cylinder and soot up the tailpipes.

- emilio

[kevinye77137]

jhm replaces valve guides in their heads

they dont exactly fail, more just get worn out. I replaced all 40 in my heads because they were so worn

in comparison to other valve guides, these are really short and will not last like guides in, for example, an LS head

crap... I should of done my valve guides when the engine was out for timing... does performing the valve guides require heads to come out?

[kevinye77137]

I know for fact I have a lot of blow by because my oil smells like gasoline even though oil has only 600 miles on it... Does anyone have this problem?

[Dirtracer603]

The 3 main reasons for oil consumption in these cars in order from easiest/cheapest to repair, it could be one, or even all at the same time: PCV valve, intake valve seals, scored cylinder walls.

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[Dirtracer603]

crap... I should of done my valve guides when the engine was out for timing... does performing the valve guides require heads to come out?

Bad valve guides wouldn't wear new valve seals out overnight, if you were still burning oil right after the seal replacement then your issue is somewhere else.

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[neilpaku]

crap... I should of done my valve guides when the engine was out for timing... does performing the valve guides require heads to come out?

Yes - they're fitted into the port from the combustion chamber side of the head. My shop charged 800 including supplying the guides

[Dirtracer603]

Yes - they're fitted into the port from the combustion chamber side of the head. My shop charged 800 including supplying the guides

$800 is cheap, assuming they recut each valve seat afterwards....

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[S4Bennett]

You should at least check the guide to stem clearance. If one cylinder is out of spec, then I'd continue to assume they're OOS across the board.

The service manual's spec is 0.80mm (0.031"). I didn't measure mine precisely at 140.5k miles but they're close or beyond the service limit so I elected to replace them.

The other piece of information that you should be mindful of is the leakdown test and what it's telling you. You can run the test with the motor out. If you block the intake and exhaust ports and the level of sound doesn't significantly change pitch, then I would open up the exploration to other openings (cylinder bore, spark plug, casting cracks).

That's my experience with guides at higher mileage in a nutshell.

[q_dubz]

It's usually one or a combination of three things:

1) Valve Seals
2) Stuck/restricted rings
3) Worn Rings

Valve seals are by far the easiest and you've already addressed that with minimal results.

People need to realize these blocks are 16~18% SILICON. That silicon makes for an extremely resilient wall which keeps it from wearing/tapering under normal conditions. This will not prevent some scratching and scores from hard ass carbon getting caught up in the ring grooves. The downside is silicon is it's very abrasive. That attribute causes the piston rings to wear fairly quickly. That's also the reason the factory pistons are iron coated on the skirts, so you don't tear the pistons up from galling.

The scoring you can't really address. Nor should you. The rings wearing are 90% of your problem.

I've spoken to techs who literally dropped in fresh rings without touching the walls and had dramatically reduced oil consumption. This has been done in both the Audi and Porsche circles however, I don't recommend that. I recommend at least using the Sunnen AN30 paste to re-expose the silicon crystals prior to installing new rings.

[kevinye77137]

It's usually one or a combination of three things:

1) Valve Seals
2) Stuck/restricted rings
3) Worn Rings

Valve seals are by far the easiest and you've already addressed that with minimal results.

People need to realize these blocks are 16~18% SILICON. That silicon makes for an extremely resilient wall which keeps it from wearing/tapering under normal conditions. This will not prevent some scratching and scores from hard ass carbon getting caught up in the ring grooves. The downside is silicon is it's very abrasive. That attribute causes the piston rings to wear fairly quickly. That's also the reason the factory pistons are iron coated on the skirts, so you don't tear the pistons up from galling.

The scoring you can't really address. Nor should you. The rings wearing are 90% of your problem.

I've spoken to techs who literally dropped in fresh rings without touching the walls and had dramatically reduced oil consumption. This has been done in both the Audi and Porsche circles however, I don't recommend that. I recommend at least using the Sunnen AN30 paste to re-expose the silicon crystals prior to installing new rings.

Thank for the information dubz now I know there is a possibility that rings CAN get stuck and not just blame everything on scored walls( Not trying to do a tear down/ replace short block). MMO should help out the stuck piston rings. So im guessing the gas smell on my fresh new oil is from my piston rings am I correct?

[emilio]

The scoring you can't really address. Nor should you. The rings wearing are 90% of your problem.

+1. i have always been skeptical of the dogma that wall scoring causes oil consumption; it's a symptom, at best, not a cause. i've scoped my cylinders and seen minor scoring, but nothing that seems to match with my 1qt per 1000mi consumption.

MMO should help out the stuck piston rings. So im guessing the gas smell on my fresh new oil is from my piston rings am I correct?

they might be stuck or they might be worn. i'm not sure MMO will help; i did a Kreen treatment & in-place piston soak (far more aggressive than MMO) and it did not seem to affect my oil consumption. if mine are stuck then it's nothing the Kreen could help, otherwise it's not because they're stuck at all - it's because they're worn.

i'm still unclear on the exact mechanism by which oil disappears, but by now i've been convinced to re-ring and hone when i'm able to.

tsk, i wonder how many people chucked serviceable engines with bad valve seals, just because they thought the cylinders were shot. the combination of Audi's tight lips and internet forum mouth-frothing hasn't done us any favors.

- emilio

[q_dubz]

I too have done the kreen treatment with minor improvement

[q_dubz]

http://rennlist.com/forums/944-turbo...it-look-4.html

Follow the procedures on this page.