Boiler Noise

[samaudio]

Hello, my boiler has been making a strange noise sporadically. It doesn’t do it all the time, just comes on for a few minutes most days and then goes back to its normal quiet hum.
I’ve attached a video so you can hear it.
Any ideas what is causing this would be really helpful.
Many thanks!

 

[terryplumb]

Is the sound eminating from the lower part of the boiler ,or higher up?

 

[samaudio]

Is the sound eminating from the lower part of the boiler ,or higher up?

It’s hard to say exactly, but I think it’s the bottom part of the boiler.

 

[terryplumb]

Pump is a likely suspect ,but you really need an engineer on site to check it out.