I have a radiator in my living room which is not getting hot, water is coming through the valves and it's been bled. I drained it and changed one of the valves' (not TRVs) when I filled the rad back up the pipe on the right hand side got hot but now it's gone cold again (valve fully open) the left hand side still has the old valve on it and is currently closed. I can post a pic of the old valve if necessary. Any help would be fantastic