deabionni

I have a '98 A8 with 190k+ miles on it, and it has developed a slight mix of oil and coolant. There is a small film of oil floating on top of the coolant in the overflow bottle, but no visible signs of coolant in the oil. (No milkshake on the dipstick). In fact, the only reason I know there's a slight trace of coolant in the oil is by the report I got back from my last oil analysts that was performed as part of it's last oil change - which I'll post here for you.



There's a sizable oil leak by the oil cooler, so at the very least, I know that changing that plastic tube and o-rings are in order. That said, other than the oil cooler itself, is there any other way that oil and coolant could be mixing in that area?

At this time, the head gaskets are not suspect as the car runs perfectly fine otherwise. There's no loss in power or performance, the engine does not overheat, and my regular commute consists of no stop drives of 2.25 hours each way. (More than enough time for the engine to overheat during driving).

The only perceivable symptoms of this problem that I notice are needing to add a little bit of coolant once every two months, and a quart of oil every couple of thousand miles.

It's time to perform the dreaded timing belt change, and I plan on fixing the oil cooler leaks while I have the car in service mode. Before ordering the parts I need, I figured I'd come here and ask about this slight mixing of oil and coolant - as I'd like to also make sure that problem is getting fixed as well. I'd hate to tear the front of this engine area apart and then find out that the problem isn't fixed - only to have to come back later and tear it all apart again.

Any input is appreciated.

Prospeeder

I would suspect the cooler itself. On other VW/Audi engines its a common failure and fills the coolant up with oil. You would think its a pressurized oil passage or it would be the other way around badly, so its not likely the head gaskets, especially if its never been overheated.

deabionni

I spoke with a tech that specialists in German cars, and he confirmed the oil cooler itself as being the problem.

As much as I'm not looking forward to removing the oil cooler as part of my timing belt change, I'd much rather that be my problem instead of a head gasket.