This manual covers the Mitsubishi S4S and S6S Diesel Engines, designed for applications such as Hyundai excavators and forklifts. These engines are recognized for their robust construction and reliable performance in demanding industrial environments. While specific production years are not detailed, the engineering principles behind these diesel powerplants emphasize durability and efficiency, making them a trusted choice for heavy-duty machinery. This comprehensive Factory Service/Repair/Workshop Manual provides essential information for maintaining and repairing the specified Mitsubishi diesel engines. It includes detailed procedures for the fuel, lubrication, cooling, inlet/exhaust, and electrical systems, along with maintenance standards, overhaul instructions, inspection and adjustment guidelines, break-in operation procedures, and performance tests. The manual is presented in English with step-by-step instructions and detailed diagrams, ensuring that owners, mechanics, and technicians have the necessary resources to keep these engines operating at peak performance.