I was on the final leg of my 60 mile snow-trek to work, and when I flicked my radio onto CD there was a few seconds of silence in the car. At this point, the car was in 4th, doing at 2,000 rpm was I in traffic. I could hear a very slight squeal-like noise. Very quiet and not really like the traditional slipping aux belt which you quite often hear when pulling away if the belt is not tight enough.

On dipping the clutch the noise went away, but returned for a few seconds after I lifted my foot back off the clutch. I checked a minute or so later and did not hear anything. I had made my way down a nicely snow covered road (about 5miles), but that was about 40 miles before hand.

Outside temp was about -1 or so if that had any bearing on it.

I will keep an ear out for future reoccurances, from a best guess it sounded central, rather than to either side of the engine bay. The fans were down on a speed setting of 1 bar (climatronic), and I don't think it was them.

Any ideas?

Clutch release bearing?....could maybe just be the cold weather affecting the brake fluid in the clutch hydraulics?

Can you turn the A/C completely off with Climatronic? The Climatic on mine sometimes makes a squealing / whirring noise when it's on but not compressing (like at the moment 'cos it's so cold), which goes away when it's turned off. Gas pressure is OK, so I'm just monitoring it for now - but that's definitely what it is for me...

I was wondering about the clutch release bearing. It had a a new clutch at about 70k (when I bought it), and don't abuse the clutch. Hopefully just as Mikey says, it was the cold weather affecting the hydraulics....

Aircon was on Econ, and from my understanding it was too cold for the aircon pump to operate. If I hear the noise again, I will turn it all off and see what happens....

Might be the clutch release bearing but, generally, that is more of a chattery clatter sound, although some cars do squeel a bit, My input shaft bearing went on my old car giving a rattly sound, the release bearing can sometimes give a tinny whine. If it hasn't been changed for 100k it could be that. Then again the heating systems make all sorts of noises.

I heard the release bearing on an ex's old volvo, that sounded like a true bag of spanners :-) I have not heard it since, but the radio was on yesterday :-)