To improve cooling efficiency by providing a wind guide wall for guiding the cooling air passed through the core of a radiator to a discharge port between the inner surface of a side wall of a bonnet having the discharge port formed thereon and the side surface of the radiator.

When an engine is operated, a fan 26 is rotated to generate a cooling air, which is then sent toward a radiator 17. The flow of the cooling air passed through the core of the radiator 17 is shaped by a wind guide wall 41 formed of first wall member 41a and second wall member 41b formed of sponge, and then discharged through the discharge port 27 of a bonnet 11. Since the cooling air passed through the core of the radiator 17 is thus shaped by the wind guide wall 41 without being returned back or disturbed, and guided to the discharge port 27, cooling efficiency can be improved. Further, since the wind guide wall 41 never interferes the bonnet 11 in the opening and closing of the bonnet, and can be prevented from being damaged, and the sealing degree is also increased, the cooling efficiency can be further more improved.