Not a gardening question, need help with a radiator
Our rads have started making a whooshing/hissing sound when turn up to number 4. I have been on You Tube and the only info I get is about bleeding. They do not need bleeding because they are hot at the top and cold at the bottom.
When we turn on the hot water tap, the noise stops for a while then comes back.
Any help or advice would be appreciated.