Can anyone please give guidence. My boiler seems to be working fine, the radiators are all working but one, which is constantly cold. I have taken the radiator off, and it looks like on the thermostatic valve side it is either blocked or the valve is faulty. However I have had the boiler on for 3 hours now, but there is no hot water, and it shows no sign of heating up. Its an old system, but has been flushed and inhibitor placed inside the system. I do have and feed & expansion tank. The radiator which is not working is upstairs, boiler upstairs. The bolier is firing okay. Thought I get as much info in as possible. Ant potential remedies on what it might be, and things that I can check.