My Worcester Bosch Greenstar combi boiler is covered under warranty so I can get someone to look at it without any problem. However, before I contact them, I would like to get an idea as to what the problem might be and whether it is the boiler itself. When the boiler cuts out due to the house being up to temperature, there is a delay of a few seconds and then a loudish clunk occurs which seems to be travelling along the pipework. This happens during the day when the boiler is switching on and off. The system pressure is in the middle of the green zone. Can anyone offer any help as to what may be causing this?
