rads not heating upstairs

[bedspoolplayer]

hi all did pump change like for like 15.50 grudfros all downstairs rads working ok upstairs not working shut off all rads d/stairs can only get bathroom rad upstairs hot three bedroom wont get hot at all had to drain down system to change pump valves alot of electric close to this i know its air anyone got any ideals how to clear this thanks in advance

 

[Puddle]

maybe a hidden two port valve for up stairs zone

 

[bedspoolplayer]

hi there is two to ports near cylinder and are working ok thanks think its a air lock poss on upstairs circult

 

[stevetheplumber]

airlock

 

[bedspoolplayer]

anyone got any ideals best way to cure this
please