We have an ongoing issue in the house with radiators not warming completely. We've spent a bit up money upgrading the heating in the house over the last few years, new oil boiler 6 years ago, some new rads, TRV's etc We also use coal as we have a back boiler too. The issue seems to be this - for no apparent reason a bedroom rad will heat fully and then maybe a few weeks later it'll only be heated on the edges. The current 'rad du jour' is a big one in the kitchen/dining. Coming down in the morning it's notably cooler than the rest of the house. I've bled the rad and it's fine and now another bedroom one is gone cooler despite the TRV being up to the max. It seems to be a sort of balancing issue but it's got no logic to it as far as I can see. Anyone got any ideas? BTW it's a 3-storey house - is it possible that the pump from the boiler isn't powerful enough and it causing this issue? We have 11 rads in total - 4 at the top of the house, 3 in the middle and 4 downstairs.