This cap is nothing more than a decorative cover, no matter how loose or tight it is, it makes no difference to the heat of the radiator.
The cap is domed and having checked the height of it, will not come into contact with the pin
It's just a cap/cover on this side. The other side is the thermostat valve which does adjust the heat but easy for kids to play with them. On the other rads I gave adjusted this side to balance them
I have been balancing the radiators throughout the house with the expectation of this and another with the same valve. The pin moves up and down when pressed but when using pliers it just spins without closing to cool the radiator or come to a stop. I have tried pushing down whilst turning but...