Hissing/Wheering Boiler

Hi,
I have an old GEM boiler in an upstairs bedroom thats quiet noisy when running.
But when not running it\\\'s very noisey at night with whirring and hissing noises. It\\\'s like wind running through the house sounds that last for 10 seconds subside then return.

I found if i turned off the water from dh to ch in the noise disappeared. I have to turn the system off thou.

Has anyone got any ideas please? The looped pipe joing dh to ch has the sound of water running through intermittenly when the system is off.

Regards Sleepyjet

It\\\'s loud enough to actually inhibit sleep

take the pipe off and see if it's leaking

There is no visible leak, and the sound would indicate quite a gush of water.