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???