Hi, just read your post. I recommend emailing DP as he helped me resolve the problem most successfully. I have moved house since then so I have a different boiler now, and as it was nearly 2 years ago I'm a bit hazy on the details, but I do remember it involved repairing/replacing the diaphragm air-pump. Talk to DP as I'm sure he knows this boiler far better than I do. Good luck.