possible cause of whistling sound coming from engine at high revs in vw bora v5

[mehlolo1979]

My 2000 VW Bora V5 makes whistling noises from the engine bay at high revs and nothing at low revs or when its idling.Anyone know what could be the possible cause?

[FastFerret]

there are clearly a bunch of reasons but my first line of investigation would be the Alternator bearings or alternator clutch on their way out.
Second would be a tensioner pulley.

[fozziebloke]

I had this problem with my V5 bora. it turned out to be the rear bearing of the alternator. Pain in the backside to try and change the bearing so save yourself the time and effort and get one from a breakers yard or EBAY. Take the alternator pully belt off and run engine for a min,that should confirm that it is nothing to sinister.