I have one radiator which is cold. I have tried bleeding the air out, and there wasn't much air in it. However, last night out of desperation I turned the temperature valves off in the rest of the house and took the screw out of the top of the radiator and let the water pour out.
This allowed the radiator to heat up, we then turned the rest of the radiators back to on and carried on bleeding and it stayed hot. The second we put the screws back in ( bleed valve screw thingys) it gets cold again.
Can anyone offer any advice as to what is happening. I am a my wits end with it all.