Ferroli Falcon CH pump clunking noise

[Welchy]

Hi guys,
I'm having problems with my Ferroli Falcon boiler. The DHW is fine with plenty of heat and pressue in the taps but the CH refuses to fire up properly. It comes on but the pump makes a horrible clunking noise and then the flame cuts out.
My Gas Safe certified mate came to have a look but couldnt come up with a solution. He had a look at the auto-air vent, he said its fine. He still thinks it has an air lock in the system somewhere. I have bled 2 pints out of each of the 4 radiators and applied the water pressure back to 1.5bar at resting.
My mate hasnt come across this boiler before but assures me the pump will be ok.
Can anyone help?
I'm not going to be doing any fiddling with it myself.

Thanks

 

[jam1979]

how can he say the pump is ok if hes not checked it it could be air in the pump or bearings on the impellar could be worn worth getting him to check this

 

[Welchy]

how can he say the pump is ok if hes not checked it it could be air in the pump or bearings on the impellar could be worn worth getting him to check this

Ok, in his opinion the pump should be fine and he think its blocked air causing the problem. Is there a way of manually bleeding air from the boiler. He did loosen the screen on the pump but water came straight out without any hiss of air

 

[Ollieg]

Sounds like its overheating on ch to me.
Are your trv's on?
I think you should get someone round (GSR) who is a bit more familiar with this boiler.