Radiator cold

I wonder if any one could help me as i am loosing my marbles with this central heating system. We have a rad in a loft donversion that is cold. If we turn the heating on and set temp over 70 it becomes slightly warm any other time you can feel it trying to get hot but it never works. It has a thermostatic thing on one side, i have checked pin and it is working fine. Rads run off a combi boiler so shouldnt have air in them. One side of rad has this thermostatic thing other just has a copper flat ended thing with a white cover over that does nothing (im sorry for crappy descriptions but i dont know technical names), anyway the pipe at this side of the radiator is cold where as the pipe at side where thermostatic doo dah is ret hot, any ideas what it may be???? Please help

emmawill said:

One side of rad has this thermostatic thing other just has a copper flat ended thing with a white cover over that does nothing

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this is called a lockshield valve and should be opened, a little adjustable spanner will do it

Firstly make sure the rad is full of water by opening the air vent a fraction. A spurt of water should emerge, or possibly air followed by water. If not, you may not have adequate pressure in the system to expel the air. What is pressure on boiler gauge and how high is this rad above the boiler?

Have you actually tried bleeding the radiator??

chrishutt said:

Firstly make sure the rad is full of water by opening the air vent a fraction. A spurt of water should emerge, or possibly air followed by water. If not, you may not have adequate pressure in the system to expel the air. What is pressure on boiler gauge and how high is this rad above the boiler?

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The air pressure is and 1 and 1/2 and goes up when heating is switched on. The rad is in loft conversion and we live in a first floor flat. I gave up and rang a plumber a while ago who has looked at it and said that he thinks there is a blockage in pipes as hes checked everything else and can see nothing wrong, he told me we can empty water from system and connect cold water pipes to rad valves to flush system backwards and hopefully get rid of blockage, he quoted 150 quid but says may not work

The air pressure is and 1 and 1/2

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You presumably mean the system water pressure. Can we assume then that you've checked for air in rad and tried turning off all the other rads to see if the top rad then gets hot?