banging radiator after heating turned off

[Jldl]

I have generally noisy central heating and hot water system, mainly i think due to sludge and expansion/contraction of pipes. One rad is a particular problem though. i turn off central heating system about an hour before go to be so most noise stops. However the radiator in my bedroom still makes a loud metallic banging sound every 5 mins or so, this goes on even about 2-3 hours after the heating has been turned off...surely if it was expansion/contraction of pipes it would have settled by then? Anything else can be? It is an old rad and when i bleed it (which it needs doing about every other week) there is dark grey water that comes out.

Please help its keeping me awake!

 

[greyback]

Sounds as if your system needs flushing.

Use a propietry Sludge remover and follow instructions on container.

I would use a couple of litres

The longer you can leave it in the better it will work.

Dont use a cleaner containing any acids.