Lockshield valve problem

[underthethumb]

I am trying to remove a radiator in my bathroom for decorating, and i am having problems with the lockshield valve.
There is a plastic cover which needs to be unsrewed off with your fingers. Once off, there is nothing underneath it, just water sitting in the pipework. I can drain the radiator with the other valve and remove the radiator, but water just trickles out of the lockshield valve end. What am I doing wrong?? Someone please help, and a plasterer is coming tomorrow morning and it needs to be off ideally!!

 

[Bahco]

There is a plastic cover which needs to be unsrewed off with your fingers. Once off, there is nothing underneath it, just water sitting in the pipework.

The plastic cover is screwed onto the radiator valve so I am slightly confused
If I were you I would drain your system down completely and remove radiator until your job is done.