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Oil in the cylinders - where's it coming from?

johnlt

New member
I recently rebuilt the engine of my 924 turbo. Well, actually it started a lot of years ago, but it was recently completed. After reinstallation it started nicely and ran for 10 minutes or so. It started ok the next morning, but after a few minutes started smoking - a cloud of smoke! Investigation has revealed there is oil pooling on top of the pistons - in all 4 cylinders.
The turbo was rebuilt, but there's no oil in the inlet pipe from the turbo, so I've discounted that as the source. I don't think the head gasket is the likely problem as it's affecting all 4 cylinders, and that also makes me think that something broken is unlikely - like a ring. So, I'm thinking it's either coming from the valves or up through the piston rings.
The block was cleaned and honed, and the rings are all new and I hope I've installed them correctly. I made notes when I fitted them and reading them through again confirms I had the correct method in mind. But, of course, I could have made a mistake. However, I can't quite get the idea of new compression rings that hold back the forces in the cylinder allowing oil to pass in any significant quantity. Yes, if they were old and worn, but new rings?
The other possibility is through the valves. The valves were lapped in and the stem oil seals were replaced. Again, though, there's always a possibility of a mistake. Could the valves have bent and could that be a cause?
I am an engineer, but only an amateur with cars, so comments from anyone with experience would be appreciated. Is there any way of confirming the source of the oil? I don't know whether to remove the head or go in through the sump to pull the pistons. Or even take the engine back out to check everything!
 
Having never owned (or been a fan of) the Turbo difficult to comment, but if all 4 cylinders are oiled would suggest that it is entering through the inlet system, either from the Turbo or the crankcase ventilation pipe. Check the compression figures first just to satisfy yourself that these are in spec.
 

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