We have a Potterton Puma that has suddenly started making the most frightening banging noises. The first time it happened we turned it off for a few hours and when we re started it all seemed ok for a few hours. It then happened again and this time there was steam coming from inside the case and out of the flue. British gas have had a look at it and said they can find nothing wrong ............ Have made sure that water pressure is up.

John A, March 2006

the wax stat needs replacing, the noise is the boiler over heating

ceri dawe, March 2008

Thanks Kev. Does the pump run for the DHW or just the radiators?

John A, March 2006

Sound to me like the pump is sticking and causing the boiler to overheat, if so yu will need to replace the pump.

Kev a boiler engineer, March 2006

Thanks to Dave Penson for his answer. If it is air in the system do you see how this could result in steam from the casing and flue?

John A, March 2006

Banging is usually due to an air-lock in the central heating system, if you follow the commisioning sequence as outlined in your boiler manual you should be able to remove the air in the system. typically, all you need to do is switch off and open the unit there will be an air bleed screw located near the pump turn it remove til lwater emerges.then remove front cover plug from the pump and rotate the pump shaft by 180 degrees using a flat head screwdriver,till water is seen smoothly coming from the system.then retighten the screws and refit the front cover.

Dave Penson, March 2006