I've just bought a (very cheap) Audi Coupe 20V, 1991, 128K on the clock and no history. It runs beautifully, except that it is blowing unburnt engine oil out of the exhaust. Oil is accumulating inside the tailpipes and dripping onto the ground at rest. Not a lot of oil, but enough to suggest there is a problem. The engine has no noticeable crankcase pressure and doesn't smoke, so I reckon the bores are OK (they usually are on the 7A engine). Passed emissions test yesterday (a non-cat test as it has been decatted at some point).
It had a reconditioned cylinder head fitted about 18 months ago, just after the previous owner bought it. He hadn't had the car long enough to know whether it used any oil before the head was done. And as the head work was under warranty, he didn't have any paperwork to show what 'reconditioned' actually meant.
So I reckon the most likely explanation is that oil is leaking down one or more of the exhaust valve stems when the car is shut down. The engine is canted over about 30 degrees, so any oil will tend to trickle out of the ports and into the downpipe. Does anyone have any other possibilities (preferably ones which don't involve removing and stripping the head)?
Looking on the bright side - thanks to its oil coating I'm not expecting the exhaust to rot from the inside out...
Richard Hall
bangernomics.tripod.com
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Not really an answer to your question, but having owned two cars in the past with worn exhaust valve guides I can say they ran beautifully except after several hours being parked - particularly overnight. Then I would get a wonderful plume of oil smoke from the exhaust just as they were started. No smoke at any other time. I'm no expert, but if you are talking about wet black oil (rather than black soot mixed with a bit of condensation) in the exhaust, then I would think it was a worn cylinder problem. How much topping up of the oil have you had to do in the short time you've had the car?
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Hi Richard,
I can only suggest that you do the compression test with/without the teaspoon of oil. My 7A engine was consuming 1 litre/200 miles prior to a rebuild. Main problem was the rings. The bores still had clearly visible hone marks at 100k miles.
Do the plugs show signs of oil?
Sad to see that Coupe 20v's are now in the bangernomics region!
BTW, I took your advice re: front suspension struts. Did all the rubber bits as well. Vast improvement in handling.
Ian.
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Thanks both of you for the helpful comments. I'll do a compression test when I get the time, butI'd be surprised if this oil was actually finding its way into the combustion chambers - it's a lovely golden colour. The plugs were clean and oil free - nice light grey electrodes, and that was after a couple of days of short journeys, not a motorway blast.
Ian, if you reckon a 20V Coupe for £800 is a lot of car for the money, what about this:
cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=2462...3
How much was one of these new? £60K? That has to be Banger of the Year (always assuming the hydraulic leak is fixable).
Richard Hall
bangernomics.tripod.com
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How much oil is the engine using ?? I can not see how the oil is not being burnt off in the down pipe and smoke out of the rear. to be carried all the way to the rear it must surely be in vapour form or you expansion box would be half full of oil. Regards Peter
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I cannot see how oil is making its way out of the exhaust pipe except from the combustion chambers. After all these are the only connection to the exhaust via the manifold. If your plugs are the right colour I don't think you can have oil going down to the exhaust, either in burnt or unburnt form. Your comment about "oil" dripping onto the drive reminds me of when my exhaust has a small hole in the tail box. When the car was parked after a short run a mixture of exhaust goo and condensation would dribble out the hole and form a pool of dark coloured liquid on the floor under the back box. Are you sure what exits from the exhaust is really oil?
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Could someone have poured oil into the exhaust either as a preservative or a joke? I really can't see how a fault could cause this, without even more obvious problems aswell.
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I doubt it is oil.reason being it would mean silencers would need to be full to point of oil draining into next silencer and so forth.due to makeup of silencer would mean an inefficient exhaust.in that while it is hot would continually carry on burning the oil to the point all you would see from exhaust is blue smoke.even after stopping the engine.after all the exhaust gets extremely hot so I doubt it is oil.as a matter of interest have you had a new exhaust fitted?
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as a matter of interest have you had a new exhaust fitted?
You might have hit the nail on the head there. New centre and back boxes.
The reason I was so ready to believe it was an engine fault is that the previous owner told me it was using a lot of oil 91 litre per 1000 miles). But I've done 250 miles since changing the oil, and as far as I can tell it hasn't used a drop. strange...
Richard Hall
bangernomics.tripod.com
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91 litre per 1000 miles.I assume that was mistyped.even 9 litres
is excessive to extreme.1 litre is even a lot at that mileage ie
per 1000 miles.I gather those engines are capable (if properly serviced)of around 400k but then I dont know the engine
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91 litre per 1000 miles.I assume that was mistyped.even 9 litres is excessive to extreme.1 litre is even a lot at that mileage ie per 1000 miles.I gather those engines are capable (if properly serviced)of around 400k but then I dont know the engine
Sorry, I meant 1 litre. In fact, I've now done around 500 miles in it and I doubt it's used more than a quarter-litre - given the age and mileage I can live with a litre every 2,000 miles.
You're right about the durability - the 7A engine is incredibly strong (I suspect because it is the non-turbo version of the 230bhp Quattro motor, and hence very understressed).
Richard Hall
bangernomics.tripod.com
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