I have the Alde 3020HE system in my Swift Challenger 480 and love it. However I've recently noticed a 'ticking' noise coming from one of the joints near a bleed valve. It coincides with the system whiring into life when its already hot and has been running for a while, and sounds typically like the pipes expanding when the hot fluid is being pushed around the syytem. Anoyingly its right under my head (when in bed), and actually wakes me up. I'm now finding that I'm starting to listen out for it, which isn't difficult!! After about 7 'ticks' it stops and the system runs extremely quitely. There is no air in the system (not that sort of noise), and the fluid is at the correct level. Any ideas? Have you noticed this?