The Komatsu S4D106 is a robust 4-cylinder, 6.4-liter diesel engine, engineered for reliability and performance across various demanding applications. Featuring direct injection fuel delivery, a water-cooled system, and a forced lubrication wet sump, this engine is built to endure. Its specifications, including a bore of 106 mm and a stroke of 115 mm, along with a typical compression ratio of 18.5:1, underscore its powerful and efficient design. The S4D106 is a testament to Komatsu's commitment to quality and durability in engine manufacturing. This Workshop Service Repair Manual provides comprehensive guidance for the Komatsu S4D106 engine. It covers essential maintenance procedures, including detailed instructions for engine oil changes and filter replacements, along with specifications for oil capacity and type. The manual also includes in-depth troubleshooting guides and diagnostic flowcharts to help identify and resolve issues efficiently. Furthermore, it details technical specifications, such as valve lash adjustments, torque curves, and rated speeds, ensuring that owners, mechanics, and technicians have all the necessary information to maintain and repair the engine effectively.