DSMblue

I have a 1992 968 that has a very annoying squeal. It doesn’t occur all the time, and normally will eventually quit after driving for a while. My guess is bad bearing(s) on the alternator, but wanted to get best thoughts from the forum. Belt is brand new and appropriately tensioned, a/c compressor is also new.

Charlie

Try a mechanic's stethoscope and see if that will help locate the noise.

Jfrahm

Could be the very common alternator belt squeal. There is a kit to add a pulley to the alternator bracket to increase the belt wrap slightly. Tension on the alternator/AC belt is also really high as per the FSM.

Tiger03447

Before you start tearing into it, have you tried belt dressing on the belt yet? Sometimes this gives a temporary solution and will give you a diagnostic as to belt or bearing. If it quits making noise, you know that it's the belt. If it squeals too much, the generated heat will glaze the belt. Then it's replacement time for that one. The stethoscope or the old screwdriver/thumb trick will let you know pronto as to the condition of the bearings.

DSMblue

Solved! Turns out that belt was indeed too loose. In the process of doing all the checking, the front bolt for the compressor fell out! Tensioned belt, reinstalled front bolt and torqued to spec. Unfortunately, somewhere in the process, the rear mount bolt disappeared. Time to order another one of those and get it installed.