Help needed please!
Recently I completely drained my combi boiler central heating system so that I could replace radiator valves. After re-pressurising the system, bleeding all the rads then re-pressurising again I turned the system on only to find the pump was making a really loud noise and was running hot. Also the heating was not getting very warm. My only idea is that as the boiler is at the highest point in the system it is full of air and is trying to pump air hence the overheat. Does this sound valid and if so how can I resolve???
Regards