I have one bolt tab that broke off the heat exchanger where it connects to the engine. Has anyone ever had this welded back on. The piece that broke off is solid and not burn by exhaust gas but the break is covered in carbon from the exhaust. Break is 1/2" long and piece is 3/8" thick. Does any one know what material the heat exchanger is made of. It is cast and could be aluminum or pot white metal.