John wrote:
I sometimes hear a noise that sounds like bubbles entering my bathroom
radiator. Thinking there must be an airlock moving I opened the
lockshield fully but the noise stopped.
I opened the air vent but no air came out.

This has happened several times - there is never any air to bleed
out. I mainly hear the noise after a shower when the combi's
motorisedvalve would be going back to heating mode.

Any ideas? (the rads are fed by double enty valves (Maxtwin))

You do know you have to bleed them when the heating is off? Best to bleed
all the rads when the air's had a bit of time to settle, I find.

Si