lentiman

2015 TDI. Drove to/from work yesterday, 90 miles no issues. Turned it on this morning and coolant error pops up: you have no coolant. Put in 3 liters! Haven’t seen a leak, but clearly it’s leaking. Does anyone know of any commonly faulty connections, etc? Otherwise I’ll look for the coolant residue to try and find where it’s coming from. Bad Q7.

dreadlocks

Was actually it low 3 liters? any smoke coming out the back? you can leak all the coolant out internally and burn it off..

If it actually has zero coolant, and you dont have a big pool of it under the vehicle.. its probably ****ed, head warped and everything already been cooked.

KevinGary

Huge plus 1!

lentiman

yep, it was actually low 3L. I’ve not seen any obvious pools of coolant. Only A/C condensate drips, or what I thought were condensate drips. Drove it a few miles this morning after adding the 3L and it’s okay. No drips, same level. Haven’t seen any white clouds Out the back but if it’s recent then I’m usually driving when it’s dark out. Going to the stealer this week for the software update so may have them take a look. Capacity is 13.2L so it didn't run dry or anything like that.

dreadlocks

If its leaking internally from a headgasket it'll smoke most right when you fire it up, cuz its been leaking all night and burning off the next morning.. so next time you cold start it in the morning get out and take a look..

keep a close eye on those fluid levels until yeh figure out how it magically lost 3l of coolant.

frqflyer

I'm pretty sure the PCV on these has coolant jacket on them. I thought I saw someone else mention they had a bad PCV that was allowing coolant to get drawn into the intake. Might be worth investigating that possibility further.

Blackfunk

There's a thread on the other Audi site specifically for the S4 dealing with unexplained coolant loss. Ironically I'm having the same issue with my S4 with 'invisible coolant loss'. The general consensus is that its leaking due to a faulty PCV - in my case I had mine replaced about three years ago now, but I do not have the burning oil typically associated with a faulty PCV.

frqflyer

A faulty typical PCV (I am not a expert on these TDIs) should not cause oil burning to my knowledgd. The oil/mist should get trapped on the baffles and return to the crank before getting up to the valve and intake. If the PCV fails closed it could cause oil leaks, but it shouldn't be getting into combustion unless you have so much blow by on your cylinders that it is ejecting large amounts of oil up into the PCV. I haven't had seen this in my cars before, but I had a large engine off a genset that did this.

cuatrokoop

On my old 4.2, the auxiliary electric coolant pump had a slight leak and it would, over time, leak and evaporate without leaving a trace.

Pothole5000

I've had leaks I couldn't find in other cars, using a pressure tester makes it super easy to track down.