There are many known problems in water cooling systems in the industrial applications such as corrosion, scale, fouling, microbiological growth, etc. Not only the same problems are expected in the cooling system of internal combustion engines but also the water leakage from cylinder liners or cylinder head to the combustion chamber has to be considered especialy if the liner pitting is the reason. In the present paper the effect of magnetic field on the engine cooling water and engine material is investigated. To compare the effectiveness of the magnetic field, the experiments were conducted at different magnetic intensities. Two different mechanisms to apply magnetic effect were compared to other treatment methods which are used commercially in the market such as anti freeze and anticorrosion fluids and systems. The magnetic devices showed an effective impact on reducing cavitation or liner pitting because of lowering surface tension of water. It showed also a noticable effect on the total hardness and pH which reduced scale, corrosion and the total suspended solids.