Anyone have any ideas what might be causing this sound....

Replaced the clutch in the ute 2 weekends ago. Used an 'extreme' clutch kit to go between an A15 and a 56A. Simply took out the old clutch, put in the new one, replaced the fluid and inspected the flywheel... did not remove the fly wheel.

First few days it worked a treat, now however after the car has sat a few hours (say overnight or while im at work) if I start it with the clutch depressed it makes a loud vibrating sound like a fan. The car starts just fine and if i leave it in neutral and release the clutch the sound stops, depress clutch and it starts again. Funny thing is if i whack it in gear and go for a drive (clutch engages and disengages perfectly) and then stop and try thr process again the noise is gone...... any ideas are appreciated??

So you didn't change pressure plate or thrust bearing. Might be mis matched clutch disk and pressure plate or more likely thrust bearing. That makes a whiring noise not a fan noise usually

Thanks unfamilia. I replaced the clutch disk and the pressure plate... the kit came with a new thrust bearing but i inspected the existing one and it was working just fine so i left it be.

A "whiring" noise is a good description of the sound.... might have to pull it out again and throw in the new bearing.......... bugger.

Yes, probably a lack of lubrication for the thrust/throwout bearing. The old pressure plate had a bit of lubrication on it. Don't put very much on the new one.

See Release Bearing.