Smoke during normal deceleration

T

tmillner

Greenie N00B Member
Hoping some one on here can help. I've done some research but would like opinions on my specific circumstances.

Car has 78k on it, bnrs4 installed about 10k ago. Running an e30 mix, at 24 to 25psi and Stratified Tune. Recently installed a occ to help with blow by.

Upon deceleration from high speeds, normal deceleration, once you stop you can see a puff of light blueish smoke fly past. Doesn't smoke at idle or during acceleration. Did a compression check all cylinders over 180 psi dry, and 185+ to 210 wet, not sure why the variance.

My research has lead me to believe valve guides on the exhaust side. There is a layer of oil in the hot side IC piping, I haven't checked the rest yet or the turbo. I'm putting a new pcv valve in tomorrow anyway but wondering if anyone had any input before I go any further with a leak down etc.



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I would do a leakdown test, as that could be it. Bad rings can give the blue smoke at decel.
 
With the leakdown if it's rings I'll read in it in the pan right? Strange this is it only does it occasionally

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How much oil are you going through? Looks like im using about a qt every 250 350 miles. Will be doing a leakdown next week.

Looking at new pistons and rods now

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Similar to your consumption, however it has reduced since I reworked my K04. I'm about to go with a different turbo, because the K04 was the first diagnosis for mass loss of oil. I need to look at rebuilding, but a college kid only has so much money. I'll have my guys do a leakdown, that sounds like the right thing to do.
 
Raider said:
I would do a leakdown test, as that could be it. Bad rings can give the blue smoke at decel.
Click to expand...
Ok leak down test complete. Here are results

Screenshot_20161016-114409.jpg
Screenshot_20161016-114455.jpg
Screenshot_20161016-115833.jpg
Screenshot_20161016-114426.jpg

Cylinder #4 had the most leakage. Had the dip stick pulled out and didn't hear any air leaking to the pan. Sounded like all the leakage was going to the exhaust.

Here is a compression test from a few weeks ago

20160925_124458.jpg
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All were 180 and above, I think there was oil in one cylinder causing it to be higher.
So right now I'm leaning more to exhaust valve seals.

Wanted to post results to see what others thought.

@Raider thoughts?


Ps if the pics don't show up I'm terrible with this app

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tmillner said:
Ok leak down test complete. Here are results

View attachment 4135
View attachment 4136
View attachment 4137
View attachment 4138

Cylinder #4 had the most leakage. Had the dip stick pulled out and didn't hear any air leaking to the pan. Sounded like all the leakage was going to the exhaust.

Here is a compression test from a few weeks ago

View attachment 4139
View attachment 4140
View attachment 4141
View attachment 4142

All were 180 and above, I think there was oil in one cylinder causing it to be higher.
So right now I'm leaning more to exhaust valve seals.

Wanted to post results to see what others thought.

@Raider thoughts?


Ps if the pics don't show up I'm terrible with this app

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Click to expand...
Guess i didnt do the twitter name thing for raider right.

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Valve seals don't affect engine compression.

I find it hard to believe that you could have 25% leakdown on all cylinders and still produce 180 psi during a compression test. Are you sure you did the leakdown test correctly?
 
VTMongoose said:
Valve seals don't affect engine compression.

I find it hard to believe that you could have 25% leakdown on all cylinders and still produce 180 psi during a compression test. Are you sure you did the leakdown test correctly?
Click to expand...
Yeah, 0 out gauge, set cylinder to tdc connect. Car still runs strong.

Compression test was to show for rings not for valve seals

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So we've eliminated turbo seals, rings, and compression looks good.. and you're still thinking exhaust valves sears, correct? Just trying to summarize and brainstorm. You stated there was oil in your hot side piping, do you have any catch can set up? The oil would have to get into the intake or piping somehow, if that's the oil that's burning upon deceleration.
 
I just replaced pcv valve and put a catch can on. Only a little residue on hot side. Don't think it's turbo seals.


I do still think exhaust seals

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get a borescope. See if you can peek at an exhaust valve while it's open in the combustion chamber. Might be hard to see but look for oil on top of the valve. If you can't see, pull the exhaust mani and look at the exhaust valves through there. If there's oil on top of them, you know it's valve guides and or stem seals.

Bad valve guides won't really show up on compression or leak down tests.
 
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Letting oil pass by into the combustion chamber during high vacuum.

I will say that there is oil on top of the pistons


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Slow6_pl said:
Because I'm a little mechanically stupid, how would the guides or seals cause oil burning?
Click to expand...

the point of valve stem seals is to prevent oil in the top end from running down the valve guides. If the seals are leaking, oil will travel down the valve guide. then it sits on top of the valve. Every time the valve opens/there is high vacuum, it can get into the combustion chamber and be burned or blown out the exhaust mani. Worn guides mean a bigger gap so it's easier for oil to get down the guide. It's pretty much impossible to measure valve guide clearance with the valves still in the head. So the tell tale sign is oil pooled on top of the valves. If the seals were not leaking, oil would not be able to pool on top of the valves. It is possible to replace valve stem seals with the head on the block. Valve stem seals aren't expensive, it's just a lot of labor. So if you diy and have time, might be worth a shot. If not, either live with oil burning or have the head pulled and new guides pressed in, get a new head. And if the head is off.......... might as well refresh the whole thing.

here is the top of the valve. If you took off your valve cover and removed the cams, buckets, valve springs, this is what you would see. The seal is the part with a coiled spring. When the engine is together and running, oil is being thrown all around in there.

1010280.jpg


so if that seal isn't working, oil travels down the guide and pools on top of the valve. So it can get burned/blown out the exhaust port

0900c15280064004.gif


this isn't entirely true all the time, but if you see oil on top of the piston, is it on the edge or in the center? Edges make me think issue with rings, center makes me think dripping down from valves.

Bad oil control rings won't really show up on compression tests either, so it could be that too. Or rings and valves at the same time
 
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mangosmoothie said:
the point of valve stem seals is to prevent oil in the top end from running down the valve guides. If the seals are leaking, oil will travel down the valve guide. then it sits on top of the valve. Every time the valve opens/there is high vacuum, it can get into the combustion chamber and be burned or blown out the exhaust mani. Worn guides mean a bigger gap so it's easier for oil to get down the guide. It's pretty much impossible to measure valve guide clearance with the valves still in the head. So the tell tale sign is oil pooled on top of the valves. If the seals were not leaking, oil would not be able to pool on top of the valves. It is possible to replace valve stem seals with the head on the block. Valve stems aren't expensive, it's just a lot of labor. So if you diy and have time, might be worth a shot. If not, either live with oil burning or have the head pulled and new guides pressed in, get a new head. And if the head is off.......... might as well refresh the whole thing.

here is the top of the valve. If you took off your valve cover and removed the cams, buckets, valve springs, this is what you would see. The seal is the part with a coiled spring. When the engine is together and running, oil is being thrown all around in there.

1010280.jpg


so if that seal isn't working, oil travels down the guide and pools on top of the valve. So it can get burned/blown out the exhaust port

0900c15280064004.gif


this isn't entirely true all the time, but if you see oil on top of the piston, is it on the edge or in the center? Edges make me think issue with rings, center makes me think dripping down from valves.

Bad oil control rings won't really show up on compression tests either, so it could be that too. Or rings and valves at the same time
Click to expand...
This is why i come here. All stuff i know but still good info and explication

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