Why are my radiators single getting hot at the bottom? My radiators downstairs are fine, they are hot at the top and...

My radiators downstairs are fine, they are hot at the top and the bottom but all my radiators upstairs, the bottom is hot but the tops of them is lately luke warm. Why is this?
The wa-wa thud contained by my brain,...
Answers:    they enjoy air within them. You need to win a radiator key and bleed them.
http://www.ultimatehandyman.co.uk/bleedi...
Fiberglass coating of wood?
They requirement 'bleeding', a little ususally brass push button that you slightly open the spigot with to permit the air out the replace when it starts 'fizzing', will soon heat up then.