Today my VRS has started to sound like it has a flock of chirping birds under the bonnet whilst at tick-over (the classic old fan belt noise). The noise disappears when the throttle is pressed and nine times out of then comes back when back at idle speed. It sounds to be coming from the alternator but also increases in intensity when the power steering is put under load. I have sprayed the belt with WD40 which had no effect at all. Does this sound like the alternator or could it be power steering pump or worse (not sure what else is run on the serpentine belt)? Any idea of costs for any of those parts?

Thanks in advance for any help.

I have been reading about the 'freewheel pulley' on the VRS alternator. Is this a removable pulley, independent to the alternator itself, which can be replaced with the belt off but the alternator still in situe?