This invention relates to a method and a device for controlling the cooling of internal combustion engines in order to reduce the corrosive wear of cylinder barrels and piston rings. The corrosion substantially is caused by the sulphur content of the fuel. In a Diesel engine the combustion of the fuel always takes place at a relatively great air excess, which implies that the formation of sulphur trioxide exceeds the formation of sulphur dioxide. Together with the water vapor in the flue gases, in addition to sulphurous acid the stronger sulphuric acid is formed. The corrosion in combination with the wear result in a much too short life of the cylinder liners and piston rings and constitute a significant economic problem. Known tests show for the corrosion of steel in flue gas with 0,01 and 0,02% SO.sub.3 -content a very distinctive maximum at about 150.degree. C., but corrosion minima on both sides of said maximum. The corrosion can be reduced by maintaining the surface temperature for cylinder barrels and piston rings below the lower temperature limit for maximum corrosion due to SO.sub.3 -content in the flue gas by tempering the coolant while the engine is subjected to a load up to a certain partial load, and at increasing output and upon arrival at said partial load causing an abrupt increase in the surface temperature to a value above the upper temperature limit for said maximum corrosion, and maintaining the surface temperature thereafter above this value by tempering of the coolant.