Hi Guys my 7a engine is smoking blue from the exhaust while driving on high rpm. The oil level going down. Are the valve stamps broken ? Or the pistonrings? can i exclude this from each other?
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Sounds like rings. Valve stem seals more prominent when you first start the car after its been sitting or when you take your foot off the throttle going down a hill. Of course you have no turbo so not that.Nothelle S2 Avant
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Without seeing it, hard to say but could be black smoke not blue when at high rpm if not running properly.
Otherwise is the dipstick correct for the engine? If even slightly over full they smoke a lot...Comment
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Could check if your crankcase breather is clean. Worth ticking it off the list. What do the plugs look like. What's the compression like . What milage is on it.
Have you done anything with the car ie oil change etc. Could be something silly
Have you got a leak down test kit ?Comment
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As above, check the compression and preferably do a leak down test to rule out anything internal. Could be over full with oil as Bowie says, also a breather system problem could be the cause.
1990 B3 2.0 80 quattro.
1992 C4 2.8 Avant quattro
1994 MTM RS2.
1998 B5 TDI quattro Sport.
2000 B5 TQS.Comment
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Hi Guys I have test the compression and a leak down test on all cilinders. All cilinders have 9/9,5bar pressure with cold engine. And the leakage are between 30 and 20 procent on all cilinders not bad isnt it? What do you Guys think of the measurements?Comment
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Cold that sounds about right, have a look at your breather arrangements, check inlet tract for excessive oil.
Could be guides, but not convinced from your description.Comment
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If your gauge is accurate it is bit down on compression, should really be around 10/10.5 but that's new and the fact all the cylinders are the same makes me doubt rings, as normally it'll just be one or two cylinder's that are wildly out compared to the others. However, your gauge could be reading a tiny bit low so who's to say...
How many times are your turning the engine over before taking a reading? I tend to go for five or six spins.
Try a hot test next see what that looks like.
Is the engine using much oil and what's the mileage? Heavily worn exhaust valve guides could cause oil to burn off, but then I'd expect it do it all the time and be really bad on start up.
Check the breather system while your at it, is there much oil in the throttle body?1990 B3 2.0 80 quattro.
1992 C4 2.8 Avant quattro
1994 MTM RS2.
1998 B5 TDI quattro Sport.
2000 B5 TQS.Comment
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it have 100.000km on it,
Checked the inlet and there is no oil in it. The compression is the same at warm engine I think you are correct if my meter is not the best quality. With a warm engine and idle the is no smoke. Only at revs there is a blue smoke. It not using much oil but is smells not good. I let the engine turn so long that the meter from compression not going more up. So 6times or something. Is it maybe the oil rings? Or do you think it is the valve stamps?
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Do you have the throttle wide open when performing the compression test?Comment
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With only 100,000km on it I seriously doubt any of the internal engine component's are at fault, that's nothing for one of these engines, its only just run in.
As long as your holding the throttle open when you do the test your doing it correctly, and the fact it's the same warm really make me doubt it's the rings.
There is one trick you could try that can help diagnose worn rings. That's to perform what's know as a wet test. Put a few drops of oil ( 5-10ml) into the cylinder via the spark plug hole before you connect up your compression tester, if the compression then jumps up when you do the test it's almost certainly the rings.1990 B3 2.0 80 quattro.
1992 C4 2.8 Avant quattro
1994 MTM RS2.
1998 B5 TDI quattro Sport.
2000 B5 TQS.Comment
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It's the rings then, almost without doubt, I'm truly amazed at that many amount of km's!!!!!!!!!!!!!!
How long have you had the car, do you know if the amount of km's is genuine?
Many be the first owner never changed the oil and thrashed the backside out of the car from new (ie not run in properly) or did something else bizarre to the engine as that really doesn't make sense at the amount of km's you think it's covered.
But from my experience a jump in compression like that is going to be ring's 99% of the time, there's nothing really else it can be.
If it was 9-9.5 bar before that's almost a 2 bar jump, which can only be the rings. You might see a 0.2/0.3 bar increase on a relatively healthy motor but not such a massive increase.
And it's like that on all cylinders?
What's the lowest cylinder read wet and what does the highest read wet?1990 B3 2.0 80 quattro.
1992 C4 2.8 Avant quattro
1994 MTM RS2.
1998 B5 TDI quattro Sport.
2000 B5 TQS.Comment
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Beware just putting rings into an old cylinder. If you have the engine out, you need a machine shop to check the bores haven't gone oval shape. No new round ring will ever seal in an oval cylinder!
Oval check and look for scoring as well. If a bore has been damaged in its past, it could be the surface damage on the bore letting the oil out, not a worn ring.Comment
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