i have a baxi bernmuda back boiler central heating system,i have had a new pump fitted as the old one used to cavitate and eventually stopped.some radiators have just cold water in them and even if i bleed them no air just cold water comes out.im told its a gravity fed system with a tank with some kind of bubble in,the first rad from boiler gets hot but all the rest towards the end seem to get colder and colder with no air in them,ive tried shutting them all off to feed the end ones and bleeding them but to no resolve help plsa s the snows on the ground

simon g, November 2010

check pump valves are open and pump running unscrew large nut in centre of pump head to release air ensure pump head is above horizontal turn to maximum speed this should release air lock if not try turning all but one of the rads off again normally the pump should be on number two speed any higher can cause air to be dragged into the system or into the pump

brian, November 2010