After draining and then refilling system had lots of trouble first with blockage from the f&e tank and then air locks. I eventually managed to get all rads hot by doing one at a time and closing all others off. But started up next morning and its back to several rads hot and a couple cold and one warm. I'm a bit stuck now , I was going to put hose on rad drain off and just let it run through with heating on and bleed each one as I go. Will this work