Zeddy

https://forums.audiworld.com/s4/msgs/2506931.phtml

S4_Cinci (I S'edTFA)

Because those are two very different things. Coolant jacket for the turbos are not analogous to the engine head. Many areas for possible coolant/oil contamination, but the turbo housing is way down the list of likely culprits. Oil cooler would be high up on the list, IMO. Typically where the coolant and oil are "near" each other, the coolant is under significant pressure at normal operating conditions, while the oil is not (oil cooler is one big exception). Oil is under higher pressure than coolant in places, but it does not usually leak into the coolant passages as the oil return passages are low pressure areas - much more common for coolant to "mysteriously disappear" as the entire cooling system is under the same pressure, and this is hard to detect exactly where mixing may be occurring.

Zeddy

My main problem is oil contamination. Blackstone has discovered a high level of coolant in my oil analysis.
I have found no visible leaks. Two different dealers have done many pressure test holding OK.
My symptoms have been a slow "evaporation of the coolant". It can be topped of and with in 3 weeks to 4 weeks that coolant CEL light comes on (check the coolant is below min. line). If I release the cap on the reservoir it rushes out which makes me believe it's under high pressure. For a long time, many of us leaned towards the after-run pump but whne physically checked, their was no visual detection of the cooant leak.
Where would you think coolant might be dissapearing to? Are there some other tests or indicators that can assist in my troubleshooting?

S4_Cinci (I S'edTFA)

warm but not hot; thus it would only leak during warm-up, but when the engine was stone cold or at full normal operating temp there would be no leak.

Is there any oil residue in the coolant expansion tank at all? If not, then it may be a real bitch to pinpoint. Oil cooler is relatively easy to check as its external to the engine, although if there is no oil in the coolant at all, I would say that is not likely the source. My next guesses would be either the RMS (rear main seal) or the head - either one of these won't be cheap to diagnose and repair. You need to be careful as that much coolant getting into the oil can trash the bearings in a short amount of time and then you'll need a new engine.

Do you ever see any milky sludge on the dipstick or underside of the oil filler cap? That would just be an indication of water hanging around for a while before evaporating. Can't give you absolutes, but coolant contaminated oil will trash an engine eventually - how many miles is only known by the Audi gods...

Zeddy

No oil in coolant expansion tank.
I have asked aboout the head seal and one of the tuner techs said it was not likely since the heads are rock solid. As you mention that coolant getting into the oil is my biggest concern. I change it every 500 miles or so.

I do not see it in the stick or underside of the filler cap.

S4_Cinci (I S'edTFA)

is likely to be are a bad RMS or a cracked block. RMS work needs the engine to come out - not cheap. Good luck.

Zeddy

pull the engine out if its the heads?

S4_Cinci (I S'edTFA)

stuff 1st. But don't just guess. Not sure what else to tell you.

Zeddy

thanks this other person B5QShip | CFDQ is having the same problem.