Hi All, Having some issues with my potterton boiler. Have replaced the diverter valve and heat exchanger as no hot water was being produced and kettling was heard. Hot water cam back for a day or two and now gone again. On firing up the gas chamber rumbles. I've had the gas chamber of and cleaned as best as. I would assume its the first clean its had since inatallation in 2012. There appears to be brown staining at the bottom of the gas chamber? Could the pilot ignition be failing at this stage causing the excess gas to rumble inside the chamber? Your help and advice is most appreciated and welcomed. Thanks in advance.