This Service Shop Repair Manual covers Komatsu Hydraulic Excavator Diesel Engines from the 68E, 74E, 82E, and 84E series, specifically detailing engine models 3D68E-3G, 3D68E-3H, 3D74E-3C, 3D82AE-3E, 3D82AE-3F, 3D84E-3F, 4D84E-3B, 4D84E-3C, and 4D84E-3D. These robust diesel engines are engineered for reliable performance in various heavy-duty applications, powering excavator models such as the PC12R-8, PC15R-8, PC20R-8, PC25R-8, PC27R-8, PC30R-8, PC35R-8, PC50UU-2, PC40R-8, and PC45R-8. The Komatsu diesel engines are known for their durability and efficiency, designed to meet the demanding operational requirements of construction and industrial environments. This comprehensive manual provides essential information for the maintenance, repair, and troubleshooting of these Komatsu engines and associated excavator components. It includes detailed step-by-step repair procedures, technical specifications, and diagnostic information for systems including the powertrain, undercarriage, hydraulic system, work equipment, engine system, and operator station. With clear illustrations, exploded diagrams, and drawings, this manual serves as an indispensable resource for owners, mechanics, and technicians to ensure optimal performance and longevity of their Komatsu equipment.