I have a 2007 A4 and I have a chirping noise whenever I start to brake. The noise lasts while I am idling. If I put the car in neutral or park the noise goes away. Once I hit the gas it goes away. I hear it every now and then while I am driving as well. It only occurs once the engine is Hot and in drive. I have 42k miles on the car.

Anyone with similar problems or ideas what could be causing the noise?

 

It was the crankcase vent valve.