Heat exchanger for gases, in particular the exhaust gases of an engine, which comprises: - a bundle of tubes intended for the circulation of the exhaust gases; - a casing that houses therein said bundle of tubes, extending longitudinally and which comprises: - a gas inlet end and a gas outlet end on which both support plates are coupled to which the ends of the tubes of said bundle of tubes are attached, communicating with the outside of the casing; and - a cooling fluid inlet orifice and a cooling fluid outlet orifice for the circulation of a cooling fluid through the inside of the casing in contact with the bundle of tubes for heat exchange with the exhaust gases circulating through same; and - means for preventing the overheating of said cooling fluid inside the casing, which comprise some deflection means arranged inside the casing and suitable for directing the flow of cooling fluid entering via said inlet orifice towards said gas inlet end; wherein said deflection means comprise at least one through-opening for access to an area of the inside of the casing adjacent to the gas inlet end, for the passage therethrough of the cooling fluid directed from the cooling fluid inlet orifice, said through-opening being arranged and dimensioned for directing a cooling fluid jet towards a sub-area of said area and wherein said deflection means comprise two or more of said through-openings (A1, A2) arranged and dimensioned for directing some respective cooling fluid jets towards various sub-areas of the area characterised in that the exchanger comprises a first column of tubes, of said bundle of tubes, stacked longitudinally, where said sub-area or each of said sub-areas covers a section of passage, in the direction of stacking, between two respective adjoining tubes of said first column of tubes. - a bundle of tubes intended for the circulation of the exhaust gases; - a casing that houses therein said bundle of tubes, extending longitudinally and which comprises: - a gas inlet end and a gas outlet end on which both support plates are coupled to which the ends of the tubes of said bundle of tubes are attached, communicating with the outside of the casing; and - a cooling fluid inlet orifice and a cooling fluid outlet orifice for the circulation of a cooling fluid through the inside of the casing in contact with the bundle of tubes for heat exchange with the exhaust gases circulating through same; and - a gas inlet end and a gas outlet end on which both support plates are coupled to which the ends of the tubes of said bundle of tubes are attached, communicating with the outside of the casing; and - a cooling fluid inlet orifice and a cooling fluid outlet orifice for the circulation of a cooling fluid through the inside of the casing in contact with the bundle of tubes for heat exchange with the exhaust gases circulating through same; and - means for preventing the overheating of said cooling fluid inside the casing, which comprise some deflection means arranged inside the casing and suitable for directing the flow of cooling fluid entering via said inlet orifice towards said gas inlet end; wherein said deflection means comprise at least one through-opening for access to an area of the inside of the casing adjacent to the gas inlet end, for the passage therethrough of the cooling fluid directed from the cooling fluid inlet orifice, said through-opening being arranged and dimensioned for directing a cooling fluid jet towards a sub-area of said area and wherein said deflection means comprise two or more of said through-openings (A1, A2) arranged and dimensioned for directing some respective cooling fluid jets towards various sub-areas of the area characterised in that the exchanger comprises a first column of tubes, of said bundle of tubes, stacked longitudinally, where said sub-area or each of said sub-areas covers a section of passage, in the direction of stacking, between two respective adjoining tubes of said first column of tubes.