radiator cold pipe warm...?

[poocatcherchampion]

can you help? the radiator is cold (but not stone cold so some heat is getting there.) the pipe on one side is hot but it doesn't seem to be getting in enough.

I've tried bleeding it but some liquid is coming out - does that mean it is bled? I've tried turning the plastic knob on the hot side but it is not keen to turn and I don't know whether to keep trying.

does anyone have any suggestions?

house and therefore heating system is about 25 years old.

thanks in advance

more info-

looks like no trvs - just an on/off knob.
also I happen to know the system has microbore/pore pipes.
and another one seems to be cold as well. both are probably the closest to the boiler.

I've seen about turning them all off and on again. I am not sure how easy it will be as many are stiff/in poor repair. anything else to try first?

thanks again - sorry this is now a bit disjointed..

is the system full of sludge? Radiator cold at the bottom, warm at the top?

Microbore can't be power flushed. Needs a chemical flush and patience.

Turn all the hot ones off. Does the cold one heat up?

You only need to turn off one end.