Need help with gurgling cold radiator, am clueless!

[rubymcqueen]

I live in a flat with only three radiators, and an ancient though recently serviced Glow-worm boiler system with header tank/cylinder.
The radiator in my front room hasn't been used all summer, when I went to turn it on yesterday, stone cold. I have tried bleeding it, but this has made no difference.Only thing i wondered, when people talk about bleeding radiators, how long should you do this for... I thought only until water appeared, which was immediately, so then i stopped.
What i have noticed is a loud gurgling water sound coming from inside radiator. Any ideas would be gratefully received!

 

[chrishutt]

Turn off other two rads and put heating on - this should force an air lock or whatever through the pipework to vent. Check that both valves on radiator are open. If this doesn't work, you've got problems.

 

[rubymcqueen]

Thank you so much! I will try that. At the risk of sounding like a complete muppet, when you say two valves... er, so i've got a temp controlled valve at one end, what is the other one i should open? Sorry 'bout this, like I said, I am clueless...