Hi all. I have had the same problem on my Audi A6 2LTR. C7 2015 diesel. My local garage pushed the serpentine belt tensioner back a little and the noise stopped so they fitted a new tensioner. All good and quiet. However they did not replace the belt as there was only 50000 miles on the clock. Apparently they should have done as approx.. 6 months later the noise is back. So back to the garage for al least a new belt not sure at this stage if I need a new tensioner. This appears to be a common problem with this TDI engine. You should be a ble to tell right away that the noise is coming from the front of the engine. Hope this is of some help. Dave R.
