This manual covers Hitachi ZX 110, 110M, 120, 130, 130LCN, 125US, 135US, and 135UR hydraulic excavators, designed for construction and earthmoving operations across various job site environments. These diesel-powered machines feature hydrostatic drive systems and are engineered by Hitachi Construction Machinery for reliability and performance. While specific horsepower, displacement, weight, length, width, and height vary by model, the consistent quality of Hitachi construction equipment ensures robust operation for demanding tasks. This troubleshooting manual provides comprehensive guidance for maintaining and repairing your Hitachi excavator. It details essential procedures, including service recommendations for hydraulic oil and oil capacity, alongside technical specifications and operating parameters. The manual is an indispensable resource for owners, mechanics, and technicians, offering the knowledge required to ensure optimal performance, longevity, and safety of the equipment through effective troubleshooting and maintenance practices.