Radiator cold at top even after bleeding

It's not impossible that it may have gotten clogged somehow.

I'd take it off, and wash it through with the hosepipe.

check your pressure gauge

Jim A

Is it a room height one? It may be relevant

The top of it is about 4 feet off the ground.

OK probably not relevant then.

snipped-for-privacy@hotmail.com presented the following explanation :

If it's a combi check the pressure gauge, otherwise make sure the header tank has water in it and is well above the top of the towel rail. For both make sure you are bleeding it with the pump off - as a pump could be creating a slight vacuum at the towel rail.

Is this a sealed system (please read the faq below)?

You haven't enough water in your CH system to fill up the radiator beyond the level it has stopped at. That is why people are telling you to check your pressure gauge, as that needs to read high enough to force water up to your upstairs radiators. If you have a sealed system you need to admit more water into it then bleed the radiators again until they fill.

Andy.

Is the top of it higher than the top of any other rad in the house?

Is the radiator level? If the bleed end is lower than the other air can accumulate in the other end. I'm not sure if CH additives stop the water dissolving oxygen or allow it as normal but render the oxygenated mix somehow less corrosive. If the former then eventually the air will redissolve in preference to the air you can get out of the system elsewhere. Actually I'd like to know which it is... ?