I have a 2002 A4 Quattro, 3.0L that had the timing belt service and all coil packs replaced back in mid December, since the morning after the install I noticed what sounded like a rubbing from the fan belt or somthing on a shroud.
I called the dealer, brought it in after work that day and the noise was gone when I got to the dealership.
The next morning the samething, I called the again, they said that it was more than likely breakin noice from the belt at start up, I explained that it sounded harmonic in nature, they said give it some time.
Well I have been driving it now for two weeks and the noise has went from slight to loud in my oppinion, and tends to go away after about an hour or so of steady driving, if it is cold it lasts longer and is louder, some days it is very slight and goes away quick, temps are between 20 - 30 degrees F.
I took it into a local repair shop for a quick look and they said it had air in the PS pump reservoir, so... that leads to my Questions; 1. How can I diagnose this correctly with out incurring additional charges, and 2. What is the procedure to remove the air from the system? (yes the reservoir is full, to the top of the MAX on the stick)
Sounds like "cavitating" - air being sucked into the vacuum side of the ps pump. Probably from a ps hose (check the hoses to the ps fluid cooler which is removed during belt service) not refitted properly or damaged during the belt service. If this is the case it could damage the pump with prolonged use, as the ps fluid is also used for lubricating the moving parts in the pump.
The timing belt tension may be to tight, When over tensioned, timing belts will "Sing" with the frequency of the belt teeth and the engine RPM until the belt is fully warmed up. Even then, seriously over tightened timing belts will sing all the time.