Altanator belt rattle sound

[Welshy_Pete]

My altanator belt has a rattle sound. If I put water on the altanator belt if clears. Also if I rev lightly it clears then comes back.

It's had a full cambelt kit with a new altanator belt fitted 10,000 miles ago. It was fine then but the last 1000 miles or less the noise started.

I think it's a pulley but not sure which one that's the problem. There must be way's to see which one it might be?

306 hdi

Thanks