Loud rushing noise from radiator

Try adjusting the valve at other end and see if it make a difference?

Depending on how old this post from that bloody web site is, the answer could be different. We have an issue like this in the room we use as a studio, but it varies as the thermostatic valve opens and closes. I'm just guessing but one supposes its the noise of the water moving through the ever changing hole it is given to pass through on the t off to the radiator. Brian

Loud rushing noises are invariably caused by turbulent flow and air pockets in the system. Switch the pump off and then bleed the noisy radiator and also whichever one(s) are highest in the system. (where any gasses tend to accumulate)

Loud rushing noises occur when there is so much air in one that it gets pumped round the other radiators and you hear the resulting turbulent flow.

Rinse and repeat until the noise goes away.

Or a uni-directional TRV fitted the wrong way round.

Tim