put a bleed key in the end of the radiator and open up the valve two or three turns (keys are found in all hardware ,d.i.y or 99p shops), air should come out and maybe a spit of water as it fills turn back off when water drips freely(it may be hot so have a towel ready and don't try to do it when system to hot. if the air /water does not come out you may not have enough presure in the system there is normaly a filling loop in the pipe work under the boiler (normaly these days this is a braided flexi pipe with a valve containing a plastic tap turn on and watch the presure valve on the boiler it should read 1.5 bar when cold top up now and adjust it again when system is cold)you should bleed out all the radiators in your house about once a mounth or as required .
big red
September 2007