Boiler noise when boiler is off

[Alexandram]

Hi. Boiler pressure was low, topped up and is now a little high, but heating was fine until it went off and a very loud banging started from the boiler. I have bled the radiators and when the boiler is on there is no noise but the minute the heating goes off the banging starts. I can only stop it by running a hot tap or switching the water off at the mains. I have just had the boiler serviced. Please can you help? (PS. I am not great with really technical terms)

 

[rod A]

HI, would suggest checking that the pump over-run is operating or you have a pump problem at high end temp range. best of luck Rod

 

[Puddle]

Hi. Boiler pressure was low, topped up and is now a little high, but heating was fine until it went off and a very loud banging started from the boiler. I have bled the radiators and when the boiler is on there is no noise but the minute the heating goes off the banging starts. I can only stop it by running a hot tap or switching the water off at the mains. I have just had the boiler serviced. Please can you help? (PS. I am not great with really technical terms)

Think maybe you have not turned filling loop off correctly after topping pressure up,and pressure release valve is opening and shutting causing banging,close filling loop correctly and check pipework from p/r stops leaking ,if not ,it will require replacing

 

[Alexandram]

Genius! Hubby hadn't closed it off fully...Thank You!!