How can I get rid of trapped air in central heating system?

After replacing the small rubber seal on the shaft of the hydraulic actuator in my BIASI 24S Combi boiler, the two radiators downstairs turned cold, I bled the system, No result, then I drained the system, filled one of the radiators with cleaning fluid, after bleeding run the system over one hour, drained the system again, filled with inhibitor and bled again, after running the central heating for an hour, the result was the same, two cold radiators, will this have anything to do with central heating pump being faulty, not being abel to push the water through the system or is there a difficult to get rid of air trapped in the system.Is there heating pump setting that I could set to higher flow. Could you please help.