Rad wont cool down - please help

[nickt]

I have a Potterton Puma 100e combi boiler which is about 3 years old.
Last week the above boiler had a new diverter valve fitted which cured a problem of the upstairs rads being hot and downstairs being cold.
Since then the rads have been heating up fine, but one of the downstairs rads will not cool down at all even when the thermostat for that rad is switched to off.(the temperature is controlled in the house by individual thermostats on each rad).
The water pressure in the system is at just over 1bar.
also
there is a noise of what sounds like rushing water coming from another one of the downstairs rads when it is switched on.

 

[ChrisR]

first
"there is a noise of what sounds like rushing water coming from another one of the downstairs rads when it is switched on."

turn down the valve at the other end til its nearly shut, say 1/2 a turn open. May need a screwdriver and pliers/small spanner, under the cap.

Hot rad - soounds like the thermostatic valve is not put together correctly, they usually shut off pretty well. If it doesn't have a trv there may be a nearby wall thermostat designed to turn the CH off?