Do any of you B6 S4 owners ever hear a noise that sounds like exactly like a toy train whistle when reving your engine from about 1k to 3k rpms?
The noise is starting to become more common and is being miss-diagnosed as an exhaust leak at the manifold. This is not correct, in order to diagnose if you have this complaint or not you must pull the front clip forwards and remove the serpintine belt and start the engine see if it goes away.
If it does the plastic idler pulley is at fault from dust getting into the bearing. This noise will **** with you because it tends to travel and it sounds like its coming from the back of the engine, if you have this noise of a toytrain whistle i would highly recommend checking it because if the belt decides to snap on you it might damage the alternator or radiator support. I should mention alternator replacement intails removing the ENGINE!!! and will charged as such. Get em checked guys.

 

I just pulled up the section on replacing the alternator in my Bentley manual, and while it is a nightmare, it does not entail removing the engine. The front bumper, headlamps and core support must come off. Looks like a $1,200 + job.

 

Well i haven't had to do one yet, but that still seems like it would suck. [:'(]