Hi, I have an 2004 A4 3.0L Avant Quattro. When I press the gas gently and a little harder, it makes this intermittent screeching whistling noise, like a metal on metal screech. I didn't notice any loss of power or anything when driving.

I parked in my driveway and opened the hood and had my wife press on the gas gently. The noise sounds like it's coming from the front of the engine or under the plastic cover that I circled in the picture. I took the cover off thinking that maybe the serpentine belt is rubbing on it or something, but the noise was still there, not sure exactly where it's coming from.

Anyone have any ideas? Thanks!

 

I would guess the noise is from a bad pulley or tensioner.

 

Could be water pump bearings, too. Did you ever have the timing belt and all the other stuff replaced? You don't mention miles, but if you're at 80-90k it is certainly time and based on age, probably past due.