Potterton boiler keeps cutting out

from the thermostat within. Last heard loud banging noises within the boiler. Have changed the water pump and the 3 way motorised valve yesterday and bled the system carefully inc. all radiators, pump itself and the bleeding valve at the top of the boiler. Any help? When switched on the system runs for approx. 10 minutes, and then the thermostat in the boiler kicks in and switches it off.

Your not very specific, to what type of system you got, but im assuming you got a potterton combi boiler. I had exactly the same problem, the boiler makes banging noises, and eventually trips out on high temp stat. I found the problem to be with the DHW flow switch sticking. When DHW is in demand, flow switch makes, but when you turn the taps off, the flow switch fails to retract back far enough for the microswitch to break, so with no taps on, and DHW on demand, water heats up within the boiler, and makes funny noises then trips.......if it is a combi, check your flow switch. Open the front panel....if the red LED is on, with no DHW in demand, then thats telling you its the flow switch.

Suresh he has a 3 way motorised valve so it isn't a combi!

Sounds like an air problem still. HOw far does the heat get , working along the pipes? Check all the valves are open. What boiler? Is the normal boiler thermostat working - ie if you turn it down while the boiler is on, does the boiler go off?