I have a Ford Focus 2.0 Ghia 2005 model with 45,000 miles on the clock. It has been making weird noises which I can only describe as sounding like someone blowing across the top of a bottle! It's been checked twice by the garage where I bought it and they say they can't find anything although they now admit there's a problem, but they don't know what it is. They tell me it's quite safe to drive but I am becoming increasingly concerned as this noise is getting louder and more persistent.

The noise seems to be coming from the front of the car and there is a low vibration which can be felt through your feet. It's not a constant noise and varies in volume. Not affected by speed. I've tried putting it in neutral when the noise happens and it makes no difference. Braking stops it but I'm told they have checked the brakes twice and all ok.

Another clue is that it makes a noise like a spring going when you drive off. Only does it once but does it every time you drive away after being parked for a while.