I have a 2012 A4 PP AT with Sport Suspension and almost 130k miles. I have a funny noise that sounds like it’s coming from inside the cabin in front of the driver’s seat behind the dashboard. It sounds like a part is loose and is free to rattle. I can hear it often when the car goes over a bump, but not every time. The only solid clue is that the noise will ALWAYS stop the instant I touch the brake pedal, no matter how light or heavy. The car runs and performs perfectly fine otherwise – brakes are fantastic and perform very well. I’ve removed the lower IP panel and inspected all the wires and brake switches while depressing the brake pedal (while the car was running in park) without seeing anything that would cause it. I’ve also removed the front driver’s wheel and inspected the entire brake and suspension system, using a small rubber hammer to try to rattle the cause and generate the noise – no luck. I’ve also inspected the space between the engine bay fire wall and the interior cabin wall – nothing seems to be out of place or looks like it would create this noise. The only thing I haven't done is take my inspection camera and have a passenger watch it while we drive. If anybody can share some thoughts or ideas on what it might be or what else I should inspect, it would be appreciated very much.

 

Finding random noises is always a problem in any vehicle. The fact that it ALWAYS goes away when you touch the brakes sure points at them as the culprit. If memory serves me, the caliper has some play in it and is not bolted down hard to anything so it can move. A bump could induce a metal on metal clicking or rattle. Applying the brakes immediately tightens the caliper down so it will not move at all. Hence noise gone. I'm not sure there is any way to fix this which is why these cars have a loud radio -- turn it up.