Part of my lockshield valve appears to be missing - can't balance the rad

[gutt3d]

One of our upstairs rooms is really cold. The rad gets nice and hot, and the noise of the water flowing through is quite loud. I figured maybe the flow is too fast, and the radiator isn't able to dump enough heat into the room, so I wanted to restrict the flow. I was all set to have a go at balancing it, but when I removed the cap on the lockshield valve, I can't see the spindle I was expecting. It looks like something's missing from the valve?

Should something be in there, and if so what's it called so I can find & buy one? If something needs to go in there, can it be installed without removing the main body of the lockshield valve, or does the system need to be drained?

Thanks!
Dan.

 

[terryplumb]

Small Allen key ( hexagonal wrench) needed .look down in the centre you will see the small hexagonal female part.
If the rad gets very hot and the room is cold ,you may need a larger radiator to accommodate the heat loss

 

[gutt3d]

So... adjust the smaller part inside? I have a set of Allen keys so I can sort that - thanks!

It's definitely possible I chose the wrong-sized rad. I'll take some measurements and see if I've messed up