E36 - belt (probably) screech

[CamB 48]

So, car is an E36 M3 Evo, 115k km, engine etc is unmodified.

It's developed a screech - sounds like a slipping belt - which only occurs at certain revs. It happens when the car is warm or cold.

I assume the problem is either the tensioner and/or the belt, and I need to replace, but am curious as to:

1) why it occurs at certain revs - between 2.5 and 4k, only ever for about 300-500rpm (a quick screech), and often when I let off the gas rather than accelerating. Is there any chance it's not the belt and something else is making the noise, or that there is a problem with the fan clutch or a/c which is causing the drag?

2) whether this is a difficult job. I assume no, but haven't got a manual to check if there's anything inherently tricky about setting the belt tension.

Thanks

[*Glenn* 854]

Remove both belts and check all the idler and tensioner bearings. Also check for play in the water pump and make sure the alternator, and AC pump pulley spins freely. Also ensure they are genuine belts ( the right size) for the tensioners to work properly. Best way is to use a stethescope to isolate where the noise is coming from.

[CamB 48]

Remove both belts and check all the idler and tensioner bearings. Also check for play in the water pump and make sure the alternator, and AC pump pulley spins freely. Also ensure they are genuine belts ( the right size) for the tensioners to work properly. Best way is to use a stethescope to isolate where the noise is coming from.

Thanks Glenn.

I actually have a problem with repeatability - I can't get it to do it when it's being free revved and can't look under the bonnet while driving.

I think I'm gonna have to bite the bullet and actually get in there and check everything. Thanks for the list of stuff to check