One cold radiator, all others working ok. Checked everything possible (except messing around with pump). Had radiator off 3 times and power flushed. On replacing the radiator the water is reasonably hot at the bottom but after bleeding heat moves to the top but cools down and is barely warm and there is no heat left at the bottom of the radiator. Because the rad has been flushed I do not think it is the radiator. Is it possible that there is not enough water flowing into the rad? I renewed the valve but water appears to only trickle into the rad.