Radiators downstairs not getting hot, had a new pump installed made no difference. When system is drained and then refilled the downstairs get hot first and when upstairs is bled then downstairs is cold again. If upstairs radiators are turned off then downstairs get warm. I have an agitator in the system at present and the pump seems to be working hard and can get noisy. One other thing to note is that when the central heating if completely switched off the upstairs radiators still get hot. Any help as it is really getting .....