This workshop service repair manual covers the Komatsu PC290LC-8 and PC290NLC-8 Hydraulic Excavators. These machines are engineered for robust performance and reliability in demanding construction and industrial environments. The manual provides comprehensive information designed to support the servicing and repair of these specific excavator models, ensuring their continued operational efficiency and longevity. The purpose of this manual is to serve as an authoritative guide for owners, mechanics, and technicians. It details essential maintenance procedures, offers a thorough troubleshooting guide with failure codes and causes, and includes complete step-by-step instructions for disassembly and assembly of key systems such as the engine, hydraulics, and electrical components. Additionally, the manual contains vital technical data, including specifications, dimension drawings, working range diagrams, and detailed parts lists, all presented with clear diagrams, drawings, and photos to facilitate accurate understanding and execution of repairs.