My problems started after I re-filled the heating system after draining down to fit TRV's to three radiators. I suspect the boiler expansion tank cold water feed line is blocked as I re-filled by using mains cold water via a hose to the boiler drain valve. The upstairs radiators do not bleed (due to lack of water?) and are only hot at the bottom and there is a water gurgling sound in the radiators. Last night I decided to "top up" the water from the mains and this seemed to work as I successfully bled all the radiators and they were piping hot. However, 20 minutes later I noticed water coming from under my Turco 70/90 oil boiler and the circulating pump started screeching after approx 15 litres of water had been mopped up. Is the boiler likely to be damaged or is there a pressure relief valve that is putting the water onto the floor? The pump impellers are turning and after using the bleed valve the pump seems to work for a while then it airlocks again. I have tried blowing the 15mm feed line in the feed tank but to no avail. Are their flexible rods available for 15mm pipe? Due to laminate flooring throughout house, I am unsure where pipes run! Should I drain the system down and try again? How do I know if the pump is really working properly (could the impellers be worn down?). Is the boiler knackered? The water tank side is a gravity system. Any ideas appreciated.