I have a potterton combi boiler and i am having issues pumping hot water round the system. I live in a two bed maisonette with 6 radiators. 4 on one side of the flat get hot but the ones in the kitchen and lounge do not get hot. It was fine a week ago and we had a new pump fitted last year. Boiler flame comes on for about five mins and goes out, I'm presuming it thinks it's heating the whole system but there is some sort of blockage? Any tips would be much appreciated. Thank you in advance.