Cold Rad after Removing

Good plumbing people!!
Tried to see the solution for this elsewhere but now hope someone recognises my problem ...
Took rad off to replaster. Theromstat control on inlet flow. Reconnected rad after plastering. Same pipework used. Bled rad. Lots of hissing and then water started to appear. All OK so far. Rad heats up at the top and is hot at the inlet thermostat.
Whole rad doesnt heat up. Is now cold and never gets any water temp change at the inlet or outlet. Switched off pump. Emptied rad (with valve closed). Changed therm. Refilled rad and bled again. Fills up but is always cold. My guess is no circulation but how to cure it? Anybody enlighten me?
Ta much in advance.
PS All other rads roastin hot Lovely
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Moderator

Moved as originally posted in WRONG FORUM (general diy)

Hi,

my advice is to alow the water in the system to cool, remove the radiator, take the radiator outdoors rum a hose pipe into the radiator and make sure any sludge is washed out.

Before reconecting the rad, open the valves on each side of the rad (one at a time) and ensure there is free flow of water from each of the valves (have a plastic pot and a towel handy to catch the water. If it gets on the carpet it could stain it black).

Also it is probably wise to check that your new thermostatic valve is bi-directional unless you know for sure which side (flow or return) it is mounted on.

did you open the locksheild

Cheers brum But I think I've covered the possible sludge interference. The water flows OK into the rad and out when I need to drain it. I think its more of circulation at the outlet connection. kevplumb - is the lockshield a part of the assembley at the outlet ie the return to the pipework? My next move is to slacken off the "joint" at the outlet (return - not the rad connection) pipework. Perhaps there is a sludge blockage at the point of microbore piping brumylad. I'll let you know. Thanks for the prompt response people

There was a problem like this recently that had us all going for quite a while - someone had replaced a radiator and it did what yours is doing. He'd managed to get either jointing paste or tape right over the end of the pipe.
It's possible thatthe lockshield valve (ie the one which isn't thermostatic, the one the other end!) has seized shut and the top isn't doing anything. If you put your eye right by it when you open it, it's bound to let water out

Nice 1 ChrisR

I was kinda thinking about avoiding the Stan Laurel approach but HEY! I could do with some cheering up.