New radiator staying cool at the bottom

[Best]

Could be anything causing slow flow through rad, - a dot of system dirt in the new TRV would easily block the tiny hole in the valve.
One of the new valves could be faulty, although rare.

 

[joni os]

Towel on floor, close both valves, then remove air vent bleed screw. Open one valve at a time. On pressurised system, water will exit rad as a jet stream and can be caught in bucket.
This will confirm both valves function correctly. Will also clear air locks in system and stands good chance of forcing through any sludge causing reduced flow through valve.
If necessary top up pressure, because when pressure drops to zero a vacuum is created and water will stop flowing from rad. Opening, closing and reopening valve and gentle tapping is often sufficient to promote flow.

 

[dougie212]

Thank you for your resposnses everyone. Joni Os, if I take the bleed screw all the way out will I not create a problem with a seal when I come to put it back in?? Or should it be ok? I was half tempted to undo at least the trv side valve and see if I could get something to pass through it. I suppose being my first experience of a trv I don't trust it really.

 

[joni os]

Your bleed screw is normally a small threaded piece of brass ending in a pointed cone internally and the square head externally. Removing and replacing should not cause problems. The greatest danger, because of its small size, is dropping it through a gap in the flooring.

 

[dougie212]

I think I have solved the problem, I drained the system, shut off all the radiators apart from the dodgy one, and with a hose attached to the drain valve and leaving it open turned the water on, let it flow through. A huge splutter of air came out and a load of black muck.. result!! now having an issue getting the boiler to ignite after refilling but thats in a new thread if you wouldn't mind having a read and seeing if you can help.. Thanks!!