Boiler noise

[simona]

I have a apollo 50/65 wall hung boiler. Approx 12 years old. Just recently it has been making loud banging noises after approx 1-2 hours when set to high. The problem is intermittent as some days it will run ok without any noise. I have introduced x2 aplications of boiler noise reducer and x1 inhibitor but problem still persists. When the boiler is on the low setting there is no problem. I have not tried a specific scale removing inhibitor yet. Is this a build up of scale and sludge and needs some TLC or a problem with the pump or both? All radiators in the house work fine. Any ideas?

 

[namsag]

Sounds like you have a faulty hi stat that over heats intermitently ,if changing it just as well to change the lo stat at same time for the sake of an extra £15 approx

 

[simona]

Thanks for getting back to me. Expanding further on this would the introduction of additional radiators to the system cause this problem? I added two extra a few weeks ago and thats when the problem started. I know that the boiler bangs when the pump is on its lowest setting. When I moved it two the mid setting it was ok until now. The pump does make cavitation noise when on the mid and high setting. It is also aprox 10 years old. Would this make the difference or do you think its just circumstantial? Many thanks again.