Never-ending coolant leak

[Avant_to_rock]

Well, the ol' 2.0t avant started leaking coolant earlier this year... at first I found the water pump was leaking so I had the full timing belt service done at around 75K. Life was good for a while until a few months later when I got back to the car after letting it sit over the weekend and the coolant light was flashing at start up and the reservoir was bone dry. I couldn't find any signs of leaking or dripping so I topped and it off and life was good again. For the next few months the car would sporadically lose coolant, sometimes more than others. During a recent oil change, my tech found the thermostat was leaking slowly. Yes, we found the issue! Replaced the thermo and the temp sensor however in the recent days after the fix, the coolant level is still dropping without any signs of puddling on the ground.

I'm at a loss here... I've owned vw/audi's for years and never had such a continuous coolant issue. Anyone experience something similar? What other problem areas should I look into? PLEASE HELP!

The victim!

[billyhoyle]

Have you checked the coolant flange? It's on the back of the engine in a pretty tight spot, and is a common source of leaks. Was this an audi tech? If so, he should know to check this.

[menace1930]

Check the area around the oil cooler. That's where mine is currently leaking. My 2.0 leaks every year! Ive replaced the rear flange, thermostat flange, and now I will be doing the oil cooler gasket.

[Theiceman]

first shine a light down on the transmission right behind the head .. if its wet it your coolant flange. you may also want to consider taking your underbody tray off for a while till oyu find it . you may not see it dripto the ground with that on.
There is also the possibility you are burning it although I don't hear of many head gasket failures on the 2.0 T. White smoke and sweet smell of exhaust are pretty good signs. IF you are really stuck you can try removing the plug and see if any of them look steam cleaned.

[hemantpd1]

Coolant flange can be the culprit. The may be degraded due to engine heat over time. In my case, I replaced the thermostat by myself as they went bad. No leaking issue. After 2-3 days my coolant was low. I suspected that I might not have installed the thermostat properly. But found that flange started leaking slowly after I fixed the thermostat. I changed the flange and all ok after that.

[Avant_to_rock]

Thanks for the quick replies! Just checked the back of the motor and there aren't any traces of coolant leaking so I think it's safe to rule out the flange.

I know after a full coolant drain and refill, the system sometimes burps and will require more coolant. I've added roughly a liter since the thermo service (2 days ago) and the level has dropped a bit since. Could the 'low' reading be from air in the system?

[hemantpd1]

1 litre seems more to me. Air should bleed out after some driving automatically.You can leave a cardboard below car for the night and check in the morning.

[Theiceman]

yeah one litre seems high but all depends how good a job you did initially in bleeding it .
keep an eye on it and also look at the bottom of the rad area in aces there are any channels catching coolant. G-12 coolant should leave a pink crusty residue that is relatively easy to spot if its an intermittent leak .