I have a coolant leak on my 2004 A6 2.7t (70k miles). I had a mechanic (European specialist) put it on a lift but after 45 minutes he could not find the source of the leak. Soit ishidden?I have to bring it back next week. It leaks a goodbit the first time driving it after topping off and then less each day after that. Any suggestions on what it might be?

 

Could be anything... Sounds like your European specialist is a dumbass though
Remove the bottom cover and put some newspapers under the car overnight. Next day look for the location of the spots on the paper, correspond to the engine, look under the car and try to trace the source t osome nearby coolant place. Also, if you have any non-coolant spots trace them as well.

Also, is it actually leaking out? May be you have blown gasket and coolant mixing with the engine oil instead %) I assume you would've noticed that though.

 

I have a 98 A4 with a 2.8. It seems to blow coolant out the expansion tank. You might want to look there for the leak.

 

I had an Audi that had a small leak that took us a year to find. It dripped on the block when things were hot and we couldn't find it.

other possible reasons.
A blown head gasket where the water is slowly leakinginto the exhaust.
Maybe a leak near the turbo.


If water is disappearing and can't be found it probably turned to steam -

 

It is located under the intake manifold. Shine a flashlight under there and see if you can spot any of the telltale pink crustys.