Engine squeal/squeak noises?

[peterabbott33]

My 2nd post today with another issue, my Megane seems to like speaking now and its driving me mad. It's a 2005 1.5 Dci86 K9K, 164,000 miles. Just fitted a new cambelt, tensioner & alternator belt as a nut had found its way into the cover and chewed the belt up, lucky escape there! Assumed this rubbing had caused the noise but after removing the strag nut and changing the above parts, the noise is still there.

The noise is a definite squeal coming from the engine bay. It happens when starting the engine, as a quick chirp, and also when turning the engine off. It also only ever seems to happen at 1300rpm, but above and below this the noise is gone! It is easily reproducible but only when under load driving, it won't squeal when revving stationary. It is not influenced by speed, itll do it at 10mph or 50mph as long as you're doing 1300rpm in any gear. It sounds like a slipping alternator belt but I've just fitted a new one. Alternator seems free and charges correctly. Water pump wasn't changed but the bearing is perfectly smooth and no leaks. There are no oil leaks or any contamination that I can find. Cambelt cover was fitted correctly and clipped in all places.

Any ideas?