This document provides comprehensive service information for Komatsu diesel engines, including models 4D98, 4D106, and S4D106. These engines are characterized by their robust inline 4-cylinder diesel configurations and water-cooling systems, designed for reliable performance in various industrial and heavy-duty applications. While specific production years are not detailed, the information is applicable across a range of models, emphasizing the engineering quality and durability inherent in Komatsu's engine design. This Workshop Service Repair Manual in English offers extensive guidance for maintaining and repairing these Komatsu engines. It covers critical areas such as detailed maintenance procedures, troubleshooting common issues, essential technical specifications, and vital safety guidelines. With hundreds of pages, this manual serves as an indispensable resource for owners, mechanics, and technicians, ensuring the longevity and optimal performance of the engine through proper care and servicing.