I have emptied my central heating system to clean it out, when I refilled it the radiators are not heating up at the bottom and 2 radiators are cold the boiler was not firing up as it usually does. It is an ideal boiler
with hot tank and tank in the roofspace. I have aired all the radiators and opened the release valve at the tank to let any air out

rob, December 2008

I wonder if you have an airlock in the pump so water isn't moving around the system? If you remove the big screw plug from the front of the pump while it is running this will allow air out (and some water - so be prepared!) You will hear the pump noise change when it starts to work properly and and will feel the pipe heat up as water moves through it. Your radiators may need bleeding again once everything is running properly.

Richard, December 2008