Hi, I have installed a new radiator tonight, complete with a TRV. This is set at 6 and the lockshield is open. But it gets luke warm across the top and stone cold at the bottom. Have felt the inlet pipe and this is boiling hot. Both radiators before and after this one are piping hot. What am I doing wrong. I have taken the TRV off and made sure the pin goes up and down. It does. Any advice.