gsaggio

Have 2013 A8 L 4.0 CPO site jan 2016 . Woke up one morning all engine coolant on driveway. was told thermostat went, they replaced it now seems to be burning through engine coolant ... only 1 1/2 months ago was full . now very low. Any suggestions . thanks Greg

MP4.2+6.0

Sounds like incomplete repair. Impossible to diagnose w/out more specificity. Since CPO (or 4/50 original warranty), I would bring it in again. If CPO, you should pay the flat amount only once for a repair and this sounds like a continuing overlapping issue. Look for pink stains or fluffy pink deposits (if dry) at coolant connections--the residue from the coolant at site of a leak.

gsaggio

Thanks I was planning to do that since it's covered. But was curious to see if this is an issue frequently encountered. No signs of leaking. But can't see much under car.

MP4.2+6.0

W/ belly pan, basically you can't see anything w/out removing it. There is likely a stain/mark on upper side of belly pan below leak. Or it could be burning off while hitting something hot or be a drip type leak that often evaporates and leaves behind the residue.

gsaggio

Thanks a million. I made an appointment to bring in.. Your input is much appreciated.. Is there any way the engine just "burns"(for lack of a better word) through the coolant this quickly? I am assuming no way... it has to be leaking somewhere? thanks again.. just want as much info as possible when i speak to the dealership... They are not always forthcoming...

MP4.2+6.0

Zero chance. Coolant does not evaporate or get consumed. If all is well, you literally can go years and not add a drop. If it loses it, it is most commonly a leak at a hose connection. Less commonly, there is an issue with the radiator or other cooler--also ends up as a leak, but may be hard to find with heat that evaporates the coolant. Or, there is a malfunction and it overheats and blows boiling water out from the pressure. When it does that (like a bad thermostat that fails closed), you normally know and have both a light show and steam underhood.

Once in a while it is a cracked reservoir bottle, sometimes on bottom where you can't see it. Or a water pump leaking at the seal. Rarely, it is the heater core (which you can detect inside as a sweet smell). Very rarely, it is an internal engine issue, most commonly with a head gasket. Engine issues end up with the coolant either going out the exhaust and can reveal themselves with lots of exhaust steam well past warm up, or go into oil that you find as milky when you open the oil fill cap.

Fortunately probably 95% are a garden variety leak, and most of the rest are radiator or an occasional water pump so it should be fixable pretty easily. And anytime there was recent work, suspect the areas near the work--untightened clamps, faulty or unreplaced o rings that are used as seals, etc. It starts though with there should be no detectable coolant level drop whatsoever. And to check it, you can put a grease pencil or similar line on the side of the reservoir at the coolant level. Mark it cold and when vehicle level and then recheck under same conditions. Or, fill exactly to one of the marks and then watch over time.

TNJohn

I dealt with a rapid coolant leak last December. The smell of coolant was strong, but no puddles above or below the belly pan that I could see. It turned out to be a cracked coolant valve left bank, which the SA said almost never fails. What has been said earlier is true - in a modern closed system the coolant level does not change over the years.