Thread: Funny Noise

The other day I had a funny noise coming from the rear right quarter panel just under the fuel filler, sometimes sounds like a fish tank pump driven by a plastic fan that is struggling to spin and other times sounds like a vibrating squeal, when we take the fuel cap off there seems an awful amount of vacuum and the sound changes when you take the cap off.

I would have thought fuel pump BUT it seems to be coming from the side of the car not from the center where the fuel pump is ( or at least I think that's where it is !)
Its as if something is touching the inside of the quarter panel and there is a heap of vibration there but that's not the only source of the sound because when we push things away from the area it lessens the sound but doesn't get rid of it.

and of course I drove it today and the sound was gone so I couldn't stick my head in there to find out what we were moving off the panel to lessen the noise.
I'm about to go away and would rather not have a surprise on my trip. So any help would be great.

Its in a v8 series 2/2002 straight petrol not on gas.