Cold Radiator - Lock valve pipe red hot - TRV pipe cold

[smell]

The last radiator on our system is cold - the pipe to the lock shield is hot - the pipe to the TRV valve is cold and cannot get it hot at all - I have closed off al the other radiator sto push the water to this radiator and still doesn't work - I have bled all the radiators when the system is cold and hot - last night I turned the radiator off that flows and return the the last one whlst bleeding it and the TRV pipe got hot a few minutes - as soon as I stopped bleeding it it went instantly cold - ecry othe radiator in the house works perfectly - I have taken the TRV top of and the pin you can push down slightly but is does move up and down so is not stuck - I have literally ran out of ideas - any advise / help would be greatly received.

 

[morlomanc]

hi
is this rad a recent addition? or been there a while? could it be sludged up?have you tried pulling water through each valve, what was the flow like through each?

 

[smell]

Rad is brand new - well a year old now - water flow perfect through both - rad has always been there - sytem been power flushed everything