I have 3 upstairs radiators, and 5 downstairs. The main one downstairs only gets lukewarm, the pipe leading to the radiator is hot, but the rad does not get very hot. There is no air in the rad, the liquid from it is clear, the system has inhibitor in it. Only if I turn off most of the other rads does it get hot. I spoke to a plumber who was too busy but suggested I get someone to power flush the system. Someone at work had it done, and thought they had wasted £400. I did see on another forum that it was suggested the pump may be inefficient, but how can you tell?