To attempt cooling by a single cooling device by cooling lubricating oil by engine cooling water in a first heat exchanging part in a cooling tank and by cooling the engine cooling water by firewater in a second heat exchanging part.

A cooling tank 34 is to heat exchange between lubricating oil, engine cooling water and firewater in a first heat exchanging part and a second heat exchanging part, and it is a single tank storing the first heat exchanging part and the second heat exchanging part. Additionally, a supply port 34a and a discharge port 34b of engine cooling water are arranged on the cooling tank 34, and connecting ports 32b, 32c of the first heat exchanging part and connecting ports 33b, 33c of the second heat exchanging part are projected and fixed on both ends. Cooling performance by air cooling is extensively lowered due to travelling of a fire truck 44 at the time of fire fighting but, as engine cooling water and lubricating oil are cooled down by using a part of firewater, overheating of engine cooling water and lubricating oil can be prevented. Consequently, it becomes possible to carry out cooling by a single cooling device and it is possible to miniaturize the cooling system.