I have a rad in an upstairs bedroom which gurgles loudly when the heating starts. Its a bit variable and can go on a bit. The rad does get hot. An extension was added from the pipes adjacent to this rad to feed a rad in the room below although I'm not sure that is the problem.
I have bled the rad and it does release a bit of air when I do and it is the only rad in the system which collects air.
Do I have some air sitting in or near to this rad? Advice appreciated. Thanks.