Banging boiler - cooling radiators

I have Glowworm Energy saver 40e (Conventional Boiler) which has been making really loud banging noises for the past year. After replacing the pump which did not solve the problem I was informed by a corgi engineer that the banging in the boiler was being caused by sludge in the system.

I have tried various chemical cleaners over the past year which also did not work. I have today paid out for a powerflush which again has not stopped the boiler from banging!!!

When we fire up the boiler the radiators heat as they should; however after about 30mins the banging starts. When a bang occurs the pilot light on the boiler goes out, it then automatically re-fires. This occurs over and over until the pilot light goes out and the radiators then start to cool. At all times the central heating remains turned on.

Any help or suggestions would be greatly appreciated.

Has the temp of the boiler been checked, the boiler stat may be dodgy

Mick, thanks for your response. No i do not believe this has been checked. I have a engineer attending on Thursday. Is this a straight forward job to repair if this is the problem?

Half hour , boiler stat more than likely gone and getting too hot or part of it is failing and stopping power going to the pump

Great. If the engineer who is attending looks at me with a blank face, like others have I will suggest this. Many Thanks