Hi, I just got a 2007 A4 quattro, 2.0 TDI 170hp engine. I have noticed an oil leak behind the engine, it seems like there is a wiring connector there leaving the head and going down the engine. Can someone tell me what I should replace/check? Thank you very much!

It could be a sensor, but I'm not sure what for. It's not uncommon for fluids to leak through where the sensors are as the seals fail over time. 

How much oil is coming out? Is it dripping or gushing out? 

Sorry, I'm not as technically mind as some of our other members :/

cheers

steve 

My father put too much oil when he did the oil change so I think it was leaking because of too much pressure. The oil level is ok now and it hasn't leaked so far. Thank you for your answer!

Your welcome:) and glad it's sorted :) 

when you over fill the system It will always find the weakest point to escape from. On top of that I also believe that some of the systems are designed to release the fluid if too much pressure has built it so as not to cause damage to the engine ;) 

cheers

steve