Noisy rads/pipes

[kentnick]

I moved property on Friday and I have found a very annoying noise!

The downstairs rads are fine but upstairs is another story, the three bedrooms knock/tap repetitively every 10 minutes and it's hard getting to sleep although today I turned on the bathroom rad/towel rail fully opened which has now reduced the tapping to a single tap every 10 minutes which I can cope with. I have bleed all the radiators and they are all free of air. Any suggestions on what is causing this? It's a combo boiler (vaillant turbomax 828e)

Thanks in advance for any info!

Nick

 

[xr4x4]

It's the sound of the pipes on the floorboards/joists as the pipes heat up expand contract.

 

[kentnick]

Why does it stop when the bathroom radiator is on though? They only make noise when he bathroom one is off