Hitachi EX300, EX300LC, EX300H, EX300LCH 1988–1991 Excavator Service Manual (P/N HU11-1A)

• Original OEM publication, P/N HU11-1A, encompassing 1,033 pages of diagrams, maintenance schedules, and assembly/disassembly documentation for major sub-systems
• Covers 1988–1991 Hitachi EX300, EX300LC, EX300H, and EX300LCH excavators, including standard and long-crawler variants
• Documents critical service intervals, torque specifications, and hydraulic circuit logic for the Hino EP100-T power plant
• Provides the essential framework for technicians maintaining EX-series hydraulic systems, superstructures, and front-end attachments
• Outlines step-by-step troubleshooting and repair for the center joint, control neutralizer valve, shockless valve, travel motor, and pilot valves
• Features essential PDF wiring diagrams, hydraulic circuit schematics, engine performance curves, PQ property charts, flow rate-pilot pressure charts, and conversion tables

Excavator System Documentation

The service manual details the operational principles and maintenance requirements for the hydraulic, electrical, and mechanical systems. It breaks down the structure and assembly of the superstructure, undercarriage, and front-end attachments, including the boom, arm, and bucket. By providing step-by-step disassembly and assembly procedures for major components—such as the KVMG-270-HC control valve and swing reduction device—this guide allows shops to tackle complex overhauls in-house instead of outsourcing to expensive dealerships. You will find dedicated sections addressing the main hydraulic circuit, pilot pump logic, and swing devices, alongside electrical system diagnostics for monitors and alarm devices. Additional chapters explain the factory procedures to fix engine faults and service fuel systems. This includes precise documentation for the Hino EP100-T engine, fuel injection pump, and turbocharger components.

Technical Reference and Specification Highlights

This documentation provides comprehensive data for unit identification and assembly maintenance. For the daily shop routine, having the exact factory test conditions and baseline metrics directly on the workbench eliminates trial-and-error, allowing mechanics to quickly evaluate pump displacement and actuator cycle times against OEM standards. Torque values are clearly mapped out for essential fasteners. For instance, swing bearing bolts require 931 N.m (687 ft.lbs), while boom cylinder pins are set at 850 N.m (627 ft.lbs). Fluid capacities are also fully detailed: the engine takes 28 liters of oil, the cooling system holds 15.5 liters, and the hydraulic tank requires 265 liters for standard operations.

When diagnosing aging EX-series excavators, technicians sometimes mistake a sluggish boom or arm response for a failing main pump. In practice, evaluating the pilot circuit frequently reveals that a clogged pilot filter, a worn HY-ZFS gear pump, or a sticking control neutralizer valve is the actual cause of the pressure drop. Understanding these specific system dynamics prevents unnecessary and costly heavy component swaps. Keep in mind that working on heavy machinery involves significant physical risks; these specifications are intended to supplement professional knowledge, so always verify procedures against the original manufacturer metrics before beginning any hands-on maintenance. The manual serves as a complete, authoritative reference for chassis, engine, and hydraulic specifications across the entire EX-series fleet.