nestoryak

alight guys, i am a tech myself for a local ford dealer just have an question about an audi which those tech are not soo easy to find willing to answer any questions. i recently bought an 03 audi a6 2.7 bi turbo car. the guy i got it from had it looked at auto haus in yorktown va. the repair order states pass side turbo failure and needs to be replaced. so i bought it for a very good price and purchased both turbos for it. well the other day i noticed a milky oil coming out of exhaust. soo i pulled it into my shop to take a look. it looks like chocolate milk is coming out of pipes. so i removed the pipes from the middle section and the boom! a half to a gallon of milky substance has come out onto the floor. i figured typical head gasket issue. but no. i did a combustion leak down test and head gasket leak test with the blue die and it did not change color or show a issue there. drained the oil, was very low and had nothing in it. but no coolant in oil. checked coolant for oil in it and nothing. removed hose off oil cooler and no oil in coolant present. so my question is, are the failed turbos mixing oil and coolant and causing that to come out the exhaust? is there another cooler of some sort i should be looking for? pulled out spark plugs and inspected and nothing unusual other that the plugs smelt like they were a little to fuel soaked. im very convinced that the coolant and oil is mixing from the failed turbos. neither is there much oil in the charge pipes, nothing more than usual. i am prepared the have to replace the engine when it comes out anyways but id rather not because this one is in still goo running shape other than it runs rough to the the bad turbos. has anyone seen this before with failed turbos? havent been able to find any info the the concern i am having.

Fabrik8

Many/most OEM turbos have lines for both coolant and oil in the CHRA, so its pretty possible that they could mix in/around the turbo and come out of the exhaust depending on the turbo failure mode. They would both have to be leaking into the CHRA obviously, so those turbos would be toast. You'd have to have a cracked CHRA because there is no other way for coolant to get to the exhaust; its a closed cavity with an inlet and outlet. Its not like the oil where a shaft seal leak can cause a direct passage to the exhaust.

So you haven't replaced the turbos with the new ones yet I gather?

nestoryak

no i havent installed new turbos yet. i will be doing that next weekend. i kind of figured that the only way its mixing and coming out the exhaust is buy the blown turbos since i have checked the oil and cooling system and combustion chambers are relatively clean. just wasnt too sure if there many be another way for oil and coolant to mix since i have little knowledge about these engines/cars.

Fabrik8

There's only two ways that it would be mixing and coming out of the exhaust, and that's either the head or the turbo. That really narrows it down, because you're not getting any pressure that is causing the two systems to mix, so both systems are coming out under pressure on their own. Usually with a head gasket you'd get mixing because combustion or compression pressure would force the systems into each other, or into whatever system is at the lower pressure if it's just across the head to block interface.

You know at least one of the turbos is bad though, so I think you've found the failure mode. I'm pretty curious about what could cause a turbo to fail like that though, probably extreme heat (from really high EGT) from a serious lean condition, or something totally weird like no anti-freeze in the coolant which could split the water jacket (if it froze). That's just a really strange failure mode for a turbo to have the coolant involved as well as the oil...

Unless the coolant is coming out of the head into the exhaust, and the oil from the turbo................

nestoryak

i dont know exactly thats what i thought was weird. the engine is actually leak free, i was very suprized about that. i think it is mixing the the chra assemblys. ill find out next weekend when i pull the engine out.

804_mini

The location of the turbos in the V6 TT engines make them very prone for premature failure due to high temperatures. When I was gathering info about B5 S4s I found that a lot of people were having to replace the stock KO3s at ~125k miles. So it's not a surprise that you are getting oil in the exhaust. My guess that the source of the water is just condensate in the exhaust that is mixing with oil.

Good opportunity to put in KO4s and chip in if hadn't already bought new KO3s

picture for reference