On 26/03/2018 09:45, Brian Gaff wrote:
That is definitely a loose something. it does not sound like its inside any
water containing parts to me. It could of course be almost anything. The
boiler sounds pretty noisy to start with, was it always that noisy? If not
you might have an issue and it just happens that its making a piece of metal
vibrate.

That's at its noisiest, and the recording has been amplified
considerably. It's not actually that noisy in use.

Was the pump unseated or moved. Often the mountings have a lot to do with
the transfer of vibrations to the structure and the loose bit you hear might
have always been there.

Couldn't see anything obvious. Some wire looms loose. But it'd take a
lot to create that sound. Another step is as you suggest - fire up
without the cover on - building up to that :-)


--
Cheers, Rob