Odd sound at start-up when cold?

[Jont999]

Car is 2002 Renault Clio 1.5 DCi, 87k
When cold engine starts normally but in the last couple of days has been joined by an odd humming noise in the background. It seems rev dependant and can be heard clearly at idle although once warm the sound disappears. The sound is the same when stationary and moving. I popped the bonnet but couldn't trace where the sound was coming from, actually I couldn't hear it, whether that's because it's being drowned out or not but is reasonably loud inside.

Any ideas before I hand it over to a garage to investigate?

thanks,
Jon

[Steve_D]

Go round the inside of the car pressing or holding various bits of trim and see if it is a harmonic vibration. Can be very difficult to find.

I had one in my 306 which turned out to be the glass of the sunroof. Doubly difficult to find as it only happened in left hand bends.

Steve

[biper]

Had this on my Pug 607,lastcouple of weeks on and off, stopped now. Assumed it was because it was so cold the fuel pump was struggling with thick desiel.
biper

[Jont999]

Yeah I didn't have it yesterday but had it again this morning. It's in the garage for a checkup anyway, I'll post back what they find.