A6 4.2 Vier

I just noticed this the other day. I will keep my eye on the level closely.

My guess is that it is leaking from the expansion tank. The design of the engine compartment keeps the heat in for a long time and gets very hot under the hood.

Any other theories?

FL C6.5 Avant

Are you actually losing fluid?
I would check the pressure cap first.

A6 4.2 Vier

I am down about 2 cups, didn't seem to go down much since I noticed it yesterday. There is no evidence of coolant on the garage floor, only on the side of the tank and the hoses underneath.

Cap holds pressure however there was some gunk on it that I wiped off yesterday. I am waiting for it to cool down before I recheck the cap today.

A6 4.2 Vier

Cap is still clean.

haloguy628

Most likely microscopic cracks in the coolant tank. Only leaks when fluid hot and under pressure. Quite common problem on V8 and V10 engines that are tightly stuffed in the engine bay and run hot.

Just search the forum and you will find quite few posts. The tank is around $20 - $25 when bought on the web. Change the cap at the same time.

A6 4.2 Vier

Thanks,
My replacement tank arrived today. I ordered some heat shield material today for my new tank. I will wait until the heat shield arrives before I put the new tank in hopes that the new tank will last longer then 7 years.

A6 4.2 Vier

Update:

I put the heat shield material on the lower portion of my new expansion tank and installed it. Hopefully it will extend the life of my new expansion tank.

The old tank looks like it had a hairline crack.