m.stamrs

Hey, new here. Looking for some technical help. I few weeks ago, my 2017 A4 quattro suddenly started pouring white smoke out the exhaust like crazy. its been parked since. I have done an exhaust gas test of the coolant tank, liquid staid blue. when I pulled the intercooler pipes, the cold side had a lot of liquid (1/2 quart approx.), and I say liquid bc it looked like oil, but most of it evaporated in the sun. I also have noticed oil/ coolant dripping from exhaust joint. oil level on dipstick is suddenly low. I was thinking blown head gasket. Since then I have done a leak down test, all 4 cylinders tested around 15%-17% leak rate. And I tested them 3 times each making sure TDC was using an borescope. I have checked PCV valve, and even switched back to the stock one that I changed out for a cheap one a year ago. I removed the O2 sensor on the turbo and stuck the camera in... oily looking in there too. Im at a point where Im thinking its the turbo.... but Im only guessing at this point. Anyone can offer some advice, I would really appreciate it. I have 80k miles in her, and I take excellent care of her.

bdh1119

I would think head gasket as well. Have you scanned with OBDeleven or similar to see if there are any codes or live data out of range?

m.stamrs

I just went out and scanned with OBD11. I have codes P003000 (oxygen sensor) makes sense bc its covered in oil and coolant. Code P218500 (Coolant temp sensor), Code P050A00 (cold start idle air control). Code P15A500 (Oil level). Code P164D00 (oil pressure warning)

bdh1119

The last two codes seem most concerning, given that, if the sensors are reporting the right information, there’s a serious loss of oil to the point pressure is low. Sometimes white smoke out the tailpipe is coolant but it can also be excessive oil burning. Did the smoke smell like burning oil when it was coming out of the tail pipe? If so, could be a broken piston ring among other possibilities. Best to have a quality euro indy shop look at it, or the dealer at much higher expense.

m.stamrs

I would expect to see oil in one or more of the cylinders ... but they all look good. seems like the oil and coolant both were just in the turbo and intercooler pipe. With all of the test ive done and what ive seen in the cylinders and the spark plugs all look really good.... I still think that it is from the turbo...? Broken rings wouldn't pass the leak down test, would it? Honestly, ive never had any issue of this type with any of my vehicles. Thats why ive done every test i can think of before ripping into the egine. Can a turbo fail in a way that coolant and oil dump into the exhaust? Both oil and coolant lines connect to the turbo.

m.stamrs

And honestly, the smoke had a smell of both coolant and oil... I knew at the time that it didnt just smell like coolant, but i thought maybe the purple stuff has a different smell than the green...

bdh1119

These are good points. Without claiming to be an expert, the turbo sounds plausible as well. If it is that, surprised that none of the codes point to it specifically. Maybe it’s functioning but damaged in a way that’s causing the other secondary issues/codes. Hopefully a pro chimes in here with something concrete to help.

bdh1119

One other comment about the codes is that, from what I read elsewhere, a bad coolant temperature sensor can cause the other code (P050A00 - cold start idle air control).

m.stamrs

Ill look into that. Thank you for your help. Makes me think more about the things I've found and other possibilities. Fortunately, I havent torn into the engine yet, not till im sure what the issue is.

1stGOAT

Blown head gasket usually billowy white smoke. Oil will be contaminated and appear milky. Coolant may also be contaminated with oil and appear darker.