Clanging wetback heater

Hi I have an Osburn 1600 wood fire and whilst there has always been minor "clanging" of the pipes when it is soked up. It has now got to the point that it wakes me up at night! Any clues as to how I could fix this?

My In-laws had an old Bosca wood and coal burning fire that when stoked up, would cause the pipes to clang - when it happened, usually the water in the pipes had started to boil. Not sure if this is what's happening with yours, but maybe try to not stoke it up so much?

It has air in the system and you will probably need to talk to a plumber about it.