have read the comments on this however have beeen bleeding rads many times to get rid of air, water comes out of bleed on rad ok.water is cool rads valves r new 2 all rads (tops)gravity system running on baxi boiler. have bled rads with pump off however when system fires up rads r cool or luke warm...checked 4 water in expansion tank and is full.taken rads off and flushed through and re placed still no good. have no zone valves on system only a pump...could this b a problem..!! may b weak, or impeller dropped off.. but is working i can hear it running...OK ANY IDEARS PLS.. should i replace pump. this is driving me mad...!!!!!!!