Noise in radiator

[John]

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))

[Mungo "Two Sheds" Toadfoot]

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

[The Natural Philosopher]

Water rushing around makes a noise as well. Could be solids as well as air..