I've got an '05 A4 and for a few months now, it has been making this really bad humming noise that sounds like it is coming from the rear of the car. I took it in to the dealer, and of course it wouldn't hum for them and they couldn't find any problems. Any clues???

 

Could be the tires. Do you notice mostly on the highway above speeds of 45? The contipros that come with the car have been noticably loud IMO. How many miles on the tires?

 

or it could be the fuel pump, maybe the suspension, wheel bearing.

 

probably a bearing. You would know if it was the fuel pump because it would be coming out of the backseat and not towards the wheels.

 

My guess is fuel pump. Yeah if it's coming from the backseat pssngr side, definitely fuel pump. I once test drove an A4 B6 78K miles on it with humming noise that came from that part of the vehicle. I belive these models are known for having fuel pump recalls. You might want to check that with Audi first and see if you're covered.

 

did you ever figure out what was wrong with your car? i have the same noise coming from the back passenger that only comes on maybe once every 2 days but its really annoying. I think it also happens if i park on any sort of incline but im not positive on that one, it could be a coincidence.

 

my car makes that same humming noise and I isolated it to the fuel filter. it was not held in place the best resulting in a slight vibration that produced a humming noise. i'd check that first. easy to fix and cheapest if all you have to do is replace the fuel filter.

 

i had the same problem..

i got the fuel pump replaced and no more humming...

 

**** i have a05 a4 how many miles did it take for the pump to go bad so i can be ready for it

 

My service advisor told me that there was a service bulletin from Audi that indicates that the problem can be the fuel filter. My car is going in Tuesday to get checked out. It had a fuel pump this past May.