Okay, this one's as old as the hills but it's happened to me and I'm stumped.
Just finished fitting small three radiators in the main bedroom, replacing one large one near the window. I did this effectively by "teeing" the pipe (it's dual-pipe feed and return, rather than single pipe in and out).
Two radiators work blisteringly well - they're too hot too touch. Third radiator, at the "end" of the system (ie that's not tee-ed) is warm but not hot. It's warm at the top but cold at the bottom.
The feed pipe going into it is too hot to touch, the thermostat on the rad is hot too, and the nub after the thermostat on the radiator itself is too hot to touch.
The return valve and pipe and at room temperature.
This indicates a problem with the return valve but I'm loathe to bleed the system AGAIN and muck around. It's also puzzling because radiators and valves are all new. Yes, I've checked to make sure I haven't got the pipes mixed up. All other radiators in house working fine and system at 1.5bar.
Any advice?