.l
gearbox
This sounds stupid but does it sound a bit like the supercharger noise on a Cooper S that gets louder as you rev it more? does it do it more in 1st gear? if so its a bearing in the gearbox that has gone it will need a gearbox re-build like mine did
dont worry though because i moaned and got it done for free
(I involved vw customer services, it must be a common fault for them to cough up. Tell them other people have had it happen to them) hope ive been of help.
Well thankfully it was carried out under warranty... but I've heard quotes range from £250-400
as it involves removing and replacing the two belts, water pump (which usually gets damaged too) and the various hoses and bits n bobs that go with the whole assembly. VW had my car for four days whilst they did the work
which is why I said I really hope it's not that thats causing the problems!
I was indulging in a little "fast-road driving" shall we say
I think I was at about 70-80 and had just overtaken a bunch of cars when I could hear the noise and pulled in to investigate... this was when I first heard the noise and it was whining whilst stationary when I pulled over and took a look under the bonnet. Turned the engine off whilst I made some phone calls and when I fired it back up the noise only really became noticeable to me over the aforementioned 2600ish revs and above...
It sounded like it was coming from down on the left of the engine bay, towards the front there where the... alternator(?) is? I think its the alternator anyway...
sorry about my limited technical knowledge but usually when something goes wrong or makes odd noises VW get it and hand it back fixed, with a bill, ha ha! 
It sounded like it was coming from down on the left of the engine bay, towards the front there where the... alternator(?) is? I think its the alternator anyway...