Vertical radiator. Water "dribbling" noises when warming up?

[Ajbrox]

evening all, we have 2 vertical rads in our bedroom. One blazes away as it should the other doesn't even get warm. (A long story but not my current question!)

The one that works as it should (i.e. Gets hot) makes a really annoying water dribbling noise, almost like someone is poring water in at the top with a jug? Is it literally just the noise of it filling up and water pouring over the top as it fills the channels? Seems a bit strange to me?its pretty annoying at 3am when the thermostat kicks in! Any ideas? Thanks.

 

[mcmoby69]

Have you bled it?

Don't forget to re charge the system if it's pressurised

 

[Roger928]

I don't think the air can be fully expelled from those.