When the radiators are on every minute or so i have a banging noise that lasts for about ten bangs.... more like a dull thudding than a bang but annoying none the less. It starts fast and by the tenth has slowed to a halt.
It happens consistantly while the heating is on and can be timed with a stopwatch.
Is it expanding pipes? Trapped air?..... Help.

Matthew Poole, December 2005

its air trapped within the system.if you have tried to bleed the the radiators and it still carrys on make sure the pump is not running then undo the large screw on the back of the pump only half a turn to let the air out.Also when bleeding the rads make sure the system is not running as you can drag air in.
let me no how you go on.

Mike, December 2005