even though there are no leaks in the plumbing and we have had a new part fitted which apparently was the course of the problem when the heating goes off the pressure drops really quickly. I put the pressure back in it stays there until the heating comes on again and then drops after,any help would be appreciated.

Bob, January 2011

It may be the expansion vessel that has lost its pressure, you need to check pressure (typically 1.5 bar )when there is no water pressure in heating system.You can check pressure with a car pressure gauge.If you cany see an expansion vessel close to filling loop its probably built into boiler

steve.e, January 2011