My Fabia 1.2 has just developed a strange noise in the engine bay.

It doesn't do it when first started, but after about 5 minutes a "whirring sound" is heard on idle.

When revved it goes away, but returns on idle again.

If i switch the engine off then restart the noise takes about 5 minutes to return.

It's quite loud and can be heard from inside the car.

I'm guessing at the fuel, or water, pump.

Any ideas?

Will it damage anything?

Could be your water pump, or alternator bearing? Whatever it is, it wont just go away or fix itself so you ought to get it checked. If its the waterpump, it will fail eventually and youll lose all your coolant.

A trip to the dealer me thinks

Here's a strange one, Filled the tank to the brim and gave the car a good "wragging" (drove a lot harder than normal) and the noise has now stopped!

Thinking it's either the fuel pump working too hard on a nearly empty tank, or because i've been driving for economy recently the idle speed had lowered somewhat, and now it's gone back up again with some spirited driving.

Weird.:confused:

Have you checked your engine cooling fan to see if it is coming on after a few minutes of idling? You will notice that if it is...after turning off the engine and restarting the fan does not start straight away. It takes a short while for the fan to restart. Just a thought.

Yes, i've tried that, it all seems to be behaving normally on that front, thanks for the suggestion anyway.