New to the thread....and Audi ownership. I have an 03 A6 2.7t quattro that I just bought and when its cold outside when i first start in the morning for roughly the first minute or two it sounds like there is an exhaust leak in the engine compartment. It completely goes away after that minute or so. I only attribute it to exhaust because of the sound. And it is defineitly in the engine compartment somewhere. Car has 76k on it. Any help appreciated. I am a service manager at a nissan dealer so I would say I am very savvy on mechanical issues but I know NOTHING about Audi.

 

It's the secondary air pump running, totally normal, mine does the same thing as yours. Somebody can chime in with better explanation, basically it has to do with the emissions on the car.

 

Stupid question but If I gave car a LITTLE bit of gas while I heard this noise should the noise get louder (talking 800 or so RPM). That is why I was thinking exhaust because its gets louder w/ RPM

 

Hey its like 03Allroad said...its the secondary air injection pump that you're hearing. Mine sounds exactly the same and the pump you hear running is located on the inside of the right front fender well..just below the headlight bucket.
Its also true what he mentioned about its purpose. It's intended to pump fresh outside air into the exhaust system ahead of the O2 sensors until the exhaust reaches a suitable temperature that the O2 sensors are able to read. It basically makes the ECU richen the fuel mixture on cold starts so that the idle is smoother as the engine warms. I owned a BMW 330I before my A6, and it sounded exactly the same on cold starts. Nothing to concern yourself about, its perfectly normal.