One Radiator doesn’t work

ThisIsWeird

Good luck - nice fix :-)

You've already said the metal pin moves freely, so it's fine. 

My sili recommendation is simply due to the valve's age, and the possibility that the rubber washer will be starting to harden - this can then weep, and the dried residue left behind can make the pin stick. Silicone is inert, will lube the washer, and won't cause it any harm. Not at all essential, but I'm a saddo who has a wee tub of the stuff just for things like this, a swivelling kitchen tap spout, and - literally a half hour ago - to lube a new fuel line for a strimmer, so's I could squeeze it through the interference hole in the petrol tank.

But not essential.

Arsenal2019

All it needed was a new TRV head acteralll and it’s working perfect now. Thank you all