Radiator not heating

[Bertharius]

I've had a large vertical radiator with new valves installed on a wall. All my other standard radiators heat up but this one only gets luke-warm. The thermostatic valve gets very hot but strangely, the inlet part of the radiator (right next to it) initially remains cool. I can feel the top part of the radiator gradually warming up slightly and eventually the whole radiator is warm, but only slightly. The thermostatic valve remains extremely hot. The lockshield valve is fully open and its outlet pipe eventually reaches the same low temperature as the radiator. What could be the problem?

 

[John.g]

Here is a similar recent thread which will, hopefully, give you some pointers.

Radiator not working | UK Plumbers Forums | Plumbers Forums

Find Radiator not working Advice and Help. How-to Radiator not working in the UK Plumbers Forums advice boards on PlumbersTalk.net - Plumbers, Gas Engineers, Bathroom Fitters - Free Advice. Radiator not working

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[cjg]

you have a air lock on the return pipe,