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Smoking at high revs

colin944

colin944

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Evening guys I'm looking for a bit of a different opinion on this one. My car smokes at high revs ( above 4 1/2 thousand revs). I'm thinking rings but what else could it be. I've rebuilt the top end with valve guides , valve stem oil seals etc. On the trip to Le mans and back she was using quite a bit of oil. She used about 2 liters there and back a round trip of about 1500 ish miles.Apart from the oil usage she seems to run very well.I'm asking just in-case there's something I can do without taking the engine out and stripping it down.

Thoughts?
 
As above, check the oil air separator system as a blockage/sealing problem can lead to high oil consumption. Is it an NA or turbo? If the former it's much easier to investigate as the turbo gets in the way on the 951... Edit: just seen it's an S2 so if you remove the inlet you should be able to access the OAS box although I've not worked on a 16v model before.

Worth trying, but when you had the head off what were the bores like?
 
Much the same as what Simon said. You have two entry points the rings or air oil seperator AOS. Actually three if you count the turbo. Have you compression checked the engine?
 
Bores are good no scoring. I haven't done a compression test yet. What is inside the air/oil separator ?
 
Not sure what's inside the AOS sealed unit but it vents pressure from the crankcase and feeds it back to the inlet. There is a device to condense oil vapour which should return to the crankcase. Inlet vacuum draws this out. You absolutely must do a compression check before you go any further.
 
Get a compression and leakdown test done, the oil may be getting past the rings somewhere.

How long ago did you have the head off?
 
Ok did a compression test tonight, results are as follows

1 195

2 200

3 200

4 195

Is that good ? sounds good to me
 
Was this hot yes? Looks good for NA engine to me. More to the point they are consistent across all four cylinders. Maybe your AOS has issues then?
 
They should improve I theory but they seem pretty tight anyway. Always best hot as that's how the engine operates. Everything is as it would be when you get the issue.
 
I believe the compression test only tells you something about the top piston ring, failure / stuck oil control ring(s) won't be detected.

Did Oli ever find the cause of his occasional S2 oil usage?
I've never really read about breather problems on an S2, so it doesn't appear to be a common issue.

Might also be worth trying the JMG suggestion of a little oil flush down the bores overnight.
 
Didn't manage to do a compression test today as my friend who has the kit wasn't in. But I decided to take a bit of the intake of and have a wee look. I found oil in the intake pipe between the air flow meter and the throttle body. It looks like its coming up through the pipe that runs from the separator to the intake.
 
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