2006 Hitachi EX120-5 Excavator Service & Operator Manual Set

This 2006 Hitachi EX120-5 excavator service manual set combines workshop repair procedures, technical troubleshooting, operating principles, and an Operator’s Manual. The operator publication applies to serial number 054557 and up; the workshop material also identifies earlier track-adjuster configurations.

• Upperstructure repair: Cab, counterweight, and main-frame removal and installation, plus pump-device, regulator, control-valve, and swing-device disassembly and assembly.

• Undercarriage service: Swing-bearing replacement, travel-motor and reduction-gear overhaul, center-joint repair, track-adjuster service, and roller and track inspection.

• Front attachment: Attachment and cylinder removal, cylinder rebuilding, hydraulic-pressure release procedures, and pin, bushing, and cylinder maintenance standards.

• Engine overhaul: Cylinder-head, piston, liner, crankshaft, and valve-train inspection and repair, with cooling, lubrication, fuel-system, and engine-electrical sections.

• Performance testing and diagnosis: Hydraulic pressure and pump-flow tests, motor-drainage checks, Dr.EX fault-code diagnosis, sensor testing, and engine-learning procedures.

• Electrical and hydraulic references: Circuit diagrams, connector layouts, harness drawings, hydraulic-flow explanations, and component section views.

• Operation and maintenance: Machine controls, transport, scheduled servicing, storage, and operating guidance for optional attachments.

The technical and workshop sections are written for experienced technicians; hydraulic testing and controller diagnosis assume suitable measuring equipment and access to the specified diagnostic tools.

Hydraulic Pumps, Valves, and Upperstructure Repair

The pump-device chapters cover the main pump, regulator, pilot pump, and drive components. Exploded views are paired with inspection standards for plungers, cylinder blocks, servo pistons, and drive-disc components, helping a shop assess wear before selecting replacement parts.

Control-valve coverage distinguishes the individual valve assemblies rather than treating the valve bank as one generic unit. Separate procedures address the right, left, and travel pilot valves, pilot shut-off valve, shockless valve, proportional solenoid valves, and pilot relief valve.

The hydraulic-pump precautions explain how trapped air in the housing can damage the pump at startup. Floating-seal guidance also identifies incorrect O-ring seating and seal alignment as causes of leakage or component damage.

Travel Gear, Track Adjusters, and Cylinders

Travel-device procedures extend into the reduction gears, travel motor, and brake valve. The center-joint section includes internal seal replacement and maintenance standards, while the front-idler and roller chapters provide disassembly views and wear checks.

Track-adjuster instructions distinguish machines up to serial number 2718 from serial number 2719 and later. Keeping that distinction visible helps match the spring configuration to the applicable service information.

Front-attachment coverage includes arm and bucket connection dimensions, cylinder inspection limits, and rebuilding procedures. Cab, counterweight, and main-frame sections specify component weights and lifting arrangements for removal work.

Engine Inspection and Repair

The engine section contains internal overhaul procedures, including cylinder-head inspection, valve-guide work, liner and piston checks, crankshaft measurements, and timing-gear assembly. Its Isuzu 4BG1/6BG1 family information requires attention to the engine-specific headings; the EX120-5 machine specifications identify the A-4BG1T engine.

Fuel-system material includes injection-nozzle servicing and injection-pump calibration data. Cooling and lubrication sections cover the water pump, thermostat, oil pump, and oil cooler. Detailed turbocharger repair is referred to a separate Mitsubishi publication.

Dr.EX Diagnosis and Circuit References

Troubleshooting separates stored fault-code diagnosis from symptom-based checks for engine, attachment, swing, and travel problems. Dr.EX monitoring information links controller inputs and outputs to the diagnostic charts, helping distinguish sensor or wiring faults from hydraulic performance problems.

Reference material includes the Main Pump P-Q Diagram, Electrical Circuit Diagram, engine harness, cab harness, relay harness, and control-valve hydraulic circuit. Electrical drawings distinguish machines produced through July 1998 from those produced beginning August 1998.

The Operator’s Manual adds routine maintenance and operating guidance for equipment such as the clamshell bucket, hydraulic breaker, crusher, and blade. These attachment sections describe operation and maintenance rather than complete internal attachment overhaul.

A Preview of Main-Pump Wear Limits

A small sample of the workshop inspection data shows how standard dimensions are distinguished from allowable wear limits.

For the main pump, plunger-to-drive-disc clearance is listed at 0.054 mm standard, with a 0.4 mm allowable limit. Plunger-bore-to-cylinder-block clearance is listed at 0.036 mm standard, with a 0.08 mm allowable limit. These component-specific comparisons support inspection during pump overhaul.

PDF Search, Diagram Detail, and Included Manuals

Search and drawing detail: PDF text search is unavailable, and there are no embedded PDF bookmarks. Large electrical and harness drawings require zooming; some small wire codes and connector labels remain difficult to read even when enlarged.

The set is supplied as one printable, English-language PDF with 1,177 pages total, divided as follows:

These counts already include introductory pages, safety sections, indexes, blank pages, and the repeated ten-page electrical-diagram attachments in both technical manuals.