Cold radiator problem

In the summer one of my gas CH radiators sprung a small leak. I shut off the water supply, drained the radiator and fixed the leak. I reintroduced the water to the radiator but when I turned the Central Heating on for the winter, this one radiator remains cold.
I have opened the bleeding valve and after about 20 minutes, the radiator gets warm as "new" hot water flows in to it, but it cools down. I've checked the thermostat valve on the radiator and it seems to be working fine. There is no air in the system and the water coming through the radiator is very clear so I doubt there is sludge.
Any ideas anyone?
Thanks,
Stew
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On Mon, 15 Dec 2003 07:06:32 +0000 (UTC), SM

For whatever reason, the flow is not happening through the radiator.
This either means that there is an airlock in one of the pipes or that the system is out of blanace, or that there is indeed, sludge.
I would start by closing all radiator valves except that for the one in question. Open its lockshield valve and turn up the pump if need be.
If that doesn't work, then it is likely that the system needs to be balanced.
.andy
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With what did you repair the leak, dear Henry ? :-)) (sorry, couldn't resist the urge)
Have you made sure that both valves are fully open ?
When you were tightening the valves back up, did you kink any of the pipes ?
Is the stuff you fixed the leak with, covering, or slightly covering, any of the water ports ?
Did you put any PTFE tape on the joints ? If you did, then make sure that it is not covering the end of the pipe or fitting when you tore it off to break it.
The thermostatic valve head is on properly ? Sitting in its key slot correctly ?
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