I did exactly as advised here and tried to chase out any airlock.
So today I drained down the system again in order to remove the x800 and attempt to recover that radiator.
Whilst drained down I took the rad off and blasted it through with a hose outside until there was no black water...
Thanks folks - sorry for the delay in replying though.
I have tried the first option there already and if left on for a few hours the rad gets tepid.
not yet taken the rad off so will be attempting that over the weekend. Thanks again.
Firstly my apologies for bringing up what is an already well debated problem. However I am stuck and the symptoms are a little unusual....
The system is open vented. All other radiators get hot within minutes of boiler firing up so I think the system is relatively healthy.
The rad in...