If you have tried to shut the air vent and it is still leaking you will need to replace it. You will need to isolate the radiator at the valves either side and let the pressure off via the air vent. Once the pressure has been released you should beable to replace the vent using some joining compound (PTFE tape)
tyemanone
December 2009
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix plumbing.