1988–1993 Hitachi EX270 Hydraulic Excavator Service Manual

This technical service manual covers maintenance, troubleshooting, and repair for the 1988–1993 Hitachi EX270 hydraulic excavator. It describes the Super Deluxe configuration; equipment on Standard and Deluxe machines can differ.

• Hydraulic pumps and valves: Main-pump and regulator disassembly, inspection, and assembly; KVMG-270-HC control-valve service and pilot-pump repair.

• Swing and travel: Motor overhauls, brake-valve service, swing and travel reduction-device rebuilding, and center-joint disassembly and assembly.

• Undercarriage and attachments: Track adjuster, roller, and link service; boom, arm, and bucket work; hydraulic-cylinder inspection and seal replacement.

• Electrical diagnosis: E-P control and monitor fault charts, wiring diagrams, circuit measurements, and diagnostic paths using a volt-ohm meter or MECHATRO CHECKER.

• Hino engine repair: Cylinder-head, timing-gear, camshaft, piston, and crankshaft procedures, supported by inspection limits and engine tune-up instructions.

• Performance and maintenance: Machine performance tests, hydraulic pressure and flow measurements, torque tables, lubrication schedules, and maintenance intervals.

Written for service personnel in training and experienced technicians, the manual combines operating theory with technical information for shop and field service.

Hydraulic Pumps, Valves, and Drive Units

The hydraulic pump section combines construction and operating theory with disassembly, inspection, bearing-preload checks, and assembly. Separate procedures cover the regulator, pump transmission, and HY-ZFS pilot gear pump.

Control-valve overhaul coverage includes spool and poppet inspection. The manual explains that the spools are selectively fitted to their housing bores and are not supplied separately for field replacement.

Control neutralizer valves, shockless valves, solenoid valves, and the mode selection cylinder have their own service sections. Serial-specific travel- and swing-motor tables help match component designs and repair procedures to the machine before parts are selected.

The travel-motor installation notes identify the mating drive splines as vulnerable to damage during assembly. Always relieve tank pressure before disconnecting hydraulic lines; escaping high-pressure fluid can cause severe injury.

Engine, Undercarriage, and Front Attachments

Hino H06C-TI coverage extends to cylinder-liner fit selection, crankshaft-bearing inspection, injection-nozzle testing, and injection-pump calibration data. Cooling and lubrication sections include pump repair, with separate overhaul instructions for the turbocharger, starter, and generator.

The engine assembly instructions warn that incorrect rocker-shaft orientation can cause valve-train seizure.

Track-tension adjustments, roller and link wear limits, and swing-bearing service are included. The front-attachment chapters add hydraulic-cylinder inspections, pin-and-bushing limits, and bucket-clearance adjustments.

E-P Control Diagnosis and Performance Testing

The optional E-P control system is documented with auto-idle, mode-selection, and travel-speed fault charts. Separate diagnostic paths use a volt-ohm meter or the optional MECHATRO CHECKER to distinguish switch and sensor faults from harness, controller, and output-circuit problems.

Hydraulic performance tests compare results against new-machine standards, recommended service limits, and limits of use. The pressure-test instructions identify gauges and adapters, including ST-6932 and ST-6450 for pilot-pressure measurement.

Main and pilot hydraulic circuit diagrams trace oil flow, while combined swing-and-travel diagrams explain shared operation. Main-pump P-Q curves, the Electrical Circuit schematic, and the Control Circuit diagram support hydraulic performance analysis and electrical fault tracing.

A Preview of Cylinder Torque and Engine Service Data

These examples are a small selection of the assembly and maintenance specifications included in the manual.

EX270 boom-cylinder data specifies a piston-nut tightening torque of 810 ± 81 kgf-m (5,856 ± 586 ft-lb). For the Hino H06C-TI engine, cold valve clearance is 0.30 mm at the inlet and 0.45 mm at the exhaust.

For cooling service, the EX270 maintenance chart lists 29 liters for cooling-water replacement.

PDF Bookmarks, Diagram Detail, and Page Count

Search, navigation, and wiring detail: Embedded bookmarks link to sections and component procedures. PDF text search is not available. Small wiring labels require magnification; some labels and lines in the control-circuit drawing are faint.

Supplied as one printable, English-language, 1,062-page PDF. Section dividers and indexes are already included in that total.