This manual covers the Hino N04C, W04D, and W04C-T diesel engines, commonly found in the Hino 300 Series trucks. These 4.0L and 3.8L, 4-cylinder, in-line, 4-cycle engines are designed for robust performance and reliability in commercial applications. The engines feature water-cooling, overhead valve (OHV) configurations, and turbocharged options for enhanced power and efficiency. This comprehensive documentation aims to support the longevity and optimal functioning of these Hino powerplants. The purpose of this workshop service and repair manual is to provide detailed instructions and specifications for the maintenance, diagnosis, and repair of the Hino N04C, W04D, and W04C-T engines. It includes essential information on general procedures, safety precautions, tightening torques, and specific system overhauls such as the cylinder head, fuel system, cooling system, and lubrication system. With step-by-step instructions and illustrations, this manual serves as an indispensable resource for both owners and professional technicians seeking to maintain and repair these engines effectively.