Back boiler not heating downstairs radiator multihead 3 pump

[Misty]

Hi I had my heating on for a few days all of a sudden there was no heating in downstairs radiators, when I turn the heating on it kicks in then turns of after 5 minutes. I have also turned up. The upstairs is heating up and pump is hot, i have bleed downstairs radiator , boiler was serviced in August but I haven't really used heating until now, I'm not sure wat I'm doing but i remember the engineer given the pump a little knock saying it was sticking and also turned something up or down near pump but I have no idea what? Please can u help I am a single lady alone and don't want to be ripped of , i have a baxi fireplace which works and the pilot light is on. Any suggestions of what I can safely try to fix please????

 

[ShaunCorbs]

Replace the pump