bleeding radiators

[clarky]

I recently had trouble with my hot water system(not heating up) which is now fine, and functioning correctly,the problem is that my radiators need bleeding, which should be straight forward, but my radiators upstairs when you open the bleed valve, the air escapes,(hisses)then stops and then nothing, no matter how long i leave valve open for, no water follows the trapped air.
The downstairs radiators are fine and "bled up".
The system is a open vent,gravity fed water system with pumped heating.
am i missing something?.

 

[breezer]

i am not a plumber or heating engineer, but if you are saying that when bleeding upstairs radiators after a while nothing happens it could be your ball cock in the loft (?) has jammed shut and is not allowing any water into the system, the downstairs radiators worked because they had water that was in the upstairs radiators to fill them.

 

[clarky]

Checked expansion tank ball cock working fine, no blockage in outlet pipe.

 

[masona]

Check all radiator valves are open upstairs & shutdown all radiator downstairs then switch on heating,the pump should force the air out.

 

[clarky]

Cheers mate, after 2 hours of pipes banging and wierd gurgling noises from expansion tank, all upstairs radiators are hot from top to bottom, thanks very much for the advice clarky