the sheet metal plate 6 is pressed into the recess 19 and deformed in plastic fashion until it takes on the shape shown in fig6 and 7 as a result of the plastic compression strain the passage 8 is produced between the base plate 5 and the sheet metal plate 6 which said passage interconnects u2014 in sealed fashion u2014 the connection fitting 9 situated on the left with the connection fitting 9 situated on the right in the step shown in fig6 the composite body 1 is subjected to an air tightness test using compressed air whereby potential leaks are detected over time by means of a drop in pressure the method described above has numerous advantages by using comparably simple diecasting moulds 12 it is possible to produce cast sheet metal composite bodies 1 having inboard passages 8 the fact that installation space can be spared overall is of central significance here the moulds 12 do not require cores which would have to be removed in expensive fashion production costs can be greatly reduced as a result in particular single component housings can be combined with heat exchangers and they can be interconnected even in the case of geometrically complex shapes when heat exchangers are involved a cooling fluid is conducted through the passages 8 so that the heat given off at the composite body 1 can be dissipated particularly efficiently since the thermal conduction paths to the cooling system are shortened moreover by using sheet metal parts the thickness of the passage walls can be.