Ideal Icos Boiler HE18 Problem with bubbling

[red2176]

Checked and drained down condensate trap line is not frozen and trap is clear, heats domestic and central heating water ok on low fire set point 4 but once burner is increased bubbling and banging starts inside the boiler. Can overcome the problem by opening the bypass around the pump but lose flow through the central heating system whilst doing this. This problem has progressed over time and is getting worse, I have checked the central heating pump and removed centre plug to release any air and the water is only trickling out of this plug even with the pump running, I thought the water would flow quite quickly but this is not the case?

Any ideas?

 

[Dannypipe]

Blocked heat exchanger?

 

[red2176]

Any ideas on how to clear this?

 

[quality]

I will more than likely be the flow stat at fault (very much doubt a blocked heat exchanger) but like everything on these boilers there made of chocolate

 

[Dannypipe]

Bubbling and banging in boiler. Bypass relieves this. Sounds like a blockage to me.

Where's Gasman when you need him?!