The Komatsu PC138US-2 is a hydraulic excavator designed for robust performance and reliability in various construction and industrial applications. This model, part of the US-2 generation, features a turbocharged diesel engine with a displacement of 4.36 L, delivering a gross power of 73.2 kW (98.2 hp) at 2000 rpm. Its hydrostatic transmission ensures efficient power delivery for travel speeds up to 5.2 km/h. With an operating weight ranging from 12900 to 13700 kg and a compact design, including a width over tracks of 2.54 m, the PC138US-2 offers a blend of power and maneuverability. This workshop service repair manual provides comprehensive guidance for the Komatsu PC138US-2. It covers essential maintenance procedures, detailed troubleshooting steps, and critical technical specifications necessary for optimal operation and longevity. The manual is intended for owners, mechanics, and technicians, offering clear instructions to ensure the excavator is maintained to the highest standards. Key areas include engine servicing, hydraulic system maintenance, and general repair information, all presented in English to facilitate understanding and accurate execution of tasks.