what's the point of asking a question if you don't read the answer i assume that you have a problem with the combustion chamber a boiler doesn't have an expansion box and you need something to seal it what you can use is fire cement and or modern replacement for asbestos rope available from central heating parts stockists if you have a Plumb Centre near they have a parts dept. the rope can be used to make seals for removable parts add a bit of water to fire cement and use small dabs to fasten it to part for permanent seals push rope into joint and cover with light application of fire cement
brian, February 2011
