I have about 105k on my 00 a6 avant and plan on changing the tiimig belt myself. at idle i can hear something running a bit rough as if some bearing is getting there. i would love to find out what it is before i start all the work so i can do it at the same time. what bearings are likely to go? could it be the waterpump which will be redone? altenator? how can i find out?

any input is appreciated!