please help

same prob as yesterday today i emptyed the system flushed through yet again put new grundfos pump on this as same as old one on the return near the back boiler filled the system back up from the mains out side to force air or any blockage water came out from the over flow let all air out from rads reset the level in the header tank lit the back boiler still not getting the hot water to all rads tried balancing. i switched all rads of bar 1
and now steam coming out in the header tank from a pipe any surgestions
as to what else might be causing the prob, it is a back boiler with header tank in loft pump on return pipe (new pump) no blockages as filled it backwards from mains am at a loss the hot water is not gravity fed as far as i know as we have a time switch for water only or heating and water

oh and the hot water from the cilinder is piping hot

As you have the same problem as yesterday, may I ask that you continue with the same post (from yesterday)

Also please note forum rules, item g