'Whirring' noise in engine
This is just a query really, as it never seems to have affected my car negatively at all, but I've always wondered why a whirring noise picks up in the engine. It's normally just at standstill, and is pretty loud, especially from the outside. It's got more frequent recently, and I can hear it whenever I come to a standstill now. It picks up for about 5-6 seconds then dies off again, and sounds like a fan spinning really fast under the bonnet.
Anyone any idea what it is? As I said, it's never affected the car, but its a bit annoying.