I have a large rad in the living room of my bungalow. when the radiator gets hot, ie not as soon as the system is switched on a quite loud series of noises begin. In a cycle varying from less than a second to 3 or 4 seconds a hissing of ascending pitch followed by a ticking/knocking noise ensues. The noise comes from the input end. The unit has normal valves and runs from 10mm copper pipe running from a manifold in the loft space. The noise stops and starts instantly when hot, when the thermostat trips in and out. I have had the unit off and flushed it through before. Would there be any point in swapping the pipes over at the manifold to reverse the flow?
Cheers
Cheers