Central heating system is Pressurised system with Combi-boiler. My fix attempts so far:
- Bleeding air out of the one radiator (with a bleed key). Immediately bled water implying no problem.
- Checked thermostatic valve (e.g. pin not stuck).
- Checked unbalanced system: in particular, I turned off all other radiators in my house to try and force a flow through the one radiator, but still it does not work.
- Flushed sludge from radiator: Took the radiator of the wall, took it outside and attached a hose to it to flush the sludge out - a lot of sludge was expelled so was hopeful this may fix it. Indeed when I reattached it to the wall, opened the valves to let the water through (as well as topping up the pressure in the entire system) the radiator got a little hot, but unfortunately quickly got cold (the pipes to/from the radiator also got hot then cold, perhaps indicating that the radiator is not requesting water?)
So I'm a bit stuck about what to do next - I'll likely try flushing the one radiator again to see if there is more sludge in there, but any help is greatly appreciated! :)