As above, when i pulled on the drive and turned the engine off there was a definite knock coming from under the bonnet, it did it about 10 times and almost sounded like the fan was catching on something but i've checked that and it's fine, i started it back up again and i think i can hear it with the engine running although a nowhere near as loud, the car seems to run fine so i'm at a bit of a loss??
Any ideas?