ionian2k

Hi all,

The dealer can't seem to isolate the root cause of my coolant loss. It has been going on since I bought the car new early last year. It is a slow loss that happens over a period of several months. The dealer just keeps topping off the coolant and sends me on my way saying something about air bubbles. The tech performed pressure and leak test and found no issue. Right now it is below the minimal mark bar again after 4 months. Incidentally over the summer my piston broke and damaged the engine block beyond repair with 17k on the odometer resulting in dealer replacing it with a new engine. I was hoping the coolant issue goes away with engine replacement. I assume it isn't normal for lose coolant like that. I don't know what to do or tell the dealer. They said they can't fix what they can't isolate and repair has to be approved by Audi.

Any good pointers will be greatly appreciated.

Civuck

my coolant loss on 2017 S3 was traced to faulty thermostat.

ionian2k

Interesting. How did they traced it to the thermostat? What was the fix? Replaced a temperature sensor?

Shan3

I also had coolant loss after about 1-1/2 years. Seems to have been fine since, but I haven't checked it recently. 2015 S3.

Civuck

Issue started with a slow coolant leak loss which I first noticed from a dashboard warning after about 10 months from delivery day. Topped it up but leak continued as observed by inspection of the reservoir over the next few days. Eventually took the car in and technician found the leak was pooling in the pan underneath the thermostat. They replaced the entire thermostat under warranty. No issues since that work 2 months ago.

19hole

There is a known issue (TSB issued) for pin holes in the overflow tank. We had the same issue and the tank was replaced.