Low humming sound

[longsword]

Our central heating boiler is situated on a short, non load bearing spur wall within the downstairs bathroom extension. This spur leads from an outside wall. There are no other rooms above or next to this wall
Until recently no problem, but now we have a humming / vibrating sound throughout the house. We've identified it as coming from the central heating by turning the boiler off and on again. We've bled all the radiators and are now stuck for a solution.

can anyone help?

 

[migoplumber]

will be either the pump or the fan.

 

[longsword]

Oh dear! I thought it might be, but was hoping that it might be a little more simple.
Thank you

 

[REDSAW]

Oh dear! I thought it might be, but was hoping that it might be a little more simple.
Thank you

you mean like a new boiler?.

 

[paul H]

could be the gas valve on its last legs

 

[longsword]

Thanks for your help. 'Twas the pump. I now have a lovely quiet house