hi my brother inlaws had probs with is rads, warm at bottom cold at top, so decided to bleed them with out turning the combi off. the system is sealed halstead finest gold combi with 4 rads up and three rads down the combi is also upstairs.since then he only gets hot water and no heating. the burner comes on when u switch it on then, switches off after a few seconds. i have re bled the system for him a number of times, even checked the pump is free and it is, from wot he tells me there can,t be a grate deal wrong with it as it was workin before he tried to bleed it. can any body give me any advise on this problem as i am trying to help him as much as i can. thx