This Service Shop Repair Manual provides comprehensive information for Komatsu Excavator engines, including Yanmar-manufactured series such as the 4D98, 4D106, and S4D106. These diesel engines are known for their robust construction and reliable performance in demanding applications. The manual covers a range of engine specifications, including displacements of approximately 3.3 L for the 4D98 series and approximately 4.0 L for the 4D106 and S4D106 series, all utilizing diesel fuel and compression ignition. While specific power outputs vary by application and are not detailed here, the inherent engineering quality of these engines ensures efficiency and durability. The purpose of this English-language manual is to serve as an authoritative guide for maintaining and repairing these Komatsu Excavator engines. It contains detailed servicing instructions and step-by-step information essential for proper upkeep. Owners, mechanics, and technicians will find valuable guidance on critical maintenance procedures, including service schedules, lubrication requirements such as oil capacity and recommended types, and technical data related to the cooling and fuel systems. This resource is designed to facilitate accurate diagnostics and effective repairs, ensuring the continued optimal operation of the equipment.