[Chaz]

Originally Posted by snapdragon

Back of engine..possibly and hopefully vacuum pump.
Just guessing but worth a closer check?

https://www.youtube.com/watch?v=U2PZ4Xklx38
https://www.youtube.com/watch?v=yYlz9pDzfsY

Wow, thanks. The Beemer video sounds similar. Ill do some digging about vacuum pumps on the 4.2TDI.