Anthony Curren
See last answer but if you can hear water run through rads probably not pump. Could be one radiator getting all the heat run heating and check all rads turn down those that heat first or turn down all upstairs rads and see if downstairs works. If not turn off all radiators except one downstairs this will send all heat to that rad and prove flow ok do this with all rads one at a time to reestablish water flow. Then turn on rads one at a time to allow flow to each rad. Failing that system may need bleeding and rads balancing.
