Hitachi EX40U/EX50U Excavator Service Manual Set (1999–2002)

Use the Technical Manual for the machine’s configuration to identify the circuit and check its performance standards. The matching Workshop Manual covers component removal, teardown, inspection, and reassembly.

The EX40u Technical Manual refers to the separate IN-01 introduction for the Type A and Type B serial-number assignments. The engine chapter covers internal engine repair. Machine-level engine removal and installation and cab removal require separate service instructions.

Search, Bookmarks, and Diagram Detail

Finding procedures and diagrams — Both PDFs have searchable text in the machine chapters and bookmarks for the technical, workshop, and engine sections. The engine chapter pages have no searchable technical text, and the “Return to Contents” bookmark points to a separate file. Small connector numbers and wire codes are easiest to read when zoomed in.

The ZIP contains two printable PDFs totaling 937 pages. That count includes both copies of the same 122-page Isuzu engine chapter, the title pages, the blank pages, and the diagram appendices.

Hydraulic Testing, Electrical Diagnosis, and Component Repair

These selected topics show the range of shop work covered. The manuals also document counterweight removal and installation and travel parking performance tests.

• Hydraulic circuits — Operation of the PG, P1, and P2 pump circuits, pilot controls, boom anti-drift and flow-combiner valves, and main and overload relief valves.
• Performance tests — Engine compression, valve clearance, injector nozzle pressure, and injection timing, plus travel and swing checks, drift and leakage tests, and hydraulic cylinder cycle times.
• Electrical diagnosis — Monitor and starting-circuit fault tracing, connector layouts, and a dedicated North American EX50u travel-alarm troubleshooting chart.
• Workshop procedures — Pump, control valve, swing motor and reduction gear, pilot valve, and solenoid valve service, with exploded assemblies, component sections, and inspection standards.
• Undercarriage and attachments — Travel drives, center joint, track adjuster, idlers, rollers, rubber tracks, front attachment, and boom, arm, bucket, boom-swing, and blade cylinders.

The procedures suit technicians equipped for hydraulic pressure testing, precision measurement, and heavy-component lifting.

Swing Brake Circuits and Serial-Specific Wiring

On the EX40u Type A, the control valve supplies the swing parking brake release signal. Type B and the EX50u use the pilot shut-off solenoid circuit. The base edition includes EX40u hydraulic and electrical drawings for both serial groups, an EX50u hydraulic circuit, and a shared electrical drawing for later EX40u machines and the EX50u. It also includes engine, main, frame, and air-conditioning harness drawings. Matching the drawing to the machine gives you the correct circuit and connector layout before tracing a fault.

The North American edition documents separate front/swing and travel pilot valves and the rotary valve that selects the SAE or ISO lever pattern. Its electrical diagram and alarm chart let you trace the travel-alarm controller, pilot-pressure inputs, buzzer, cancel switch, and harness connections together.

Hydraulic Overhaul and Isuzu Engine Repair

The control valve procedures reach the relief and make-up valves, direct-acting and pilot-operated spools, and the flow-combiner valve. Swing device service covers reduction-gear bearing preload and the parking-brake switch valve. The workshop text identifies where pump, motor, and cylinder work calls for air bleeding, where a press is specified for the swing brake piston, and which pilot-valve spools and shims must stay matched to their ports.

Tool references include ST6077 and ST6933 for main-pump pressure checks, ST6627 for swing and travel motor case-drain tests, and ST7924 for pilot-valve work. The workshop volumes also give tightening torques, piping-joint data, wear limits, and pressure-release, blocking, and lifting precautions.

The Isuzu engine chapter gives 4LE1-specific entries in its engine-family tables, with procedures for internal teardown, inspection, repair, and reassembly. It covers oil and coolant circulation, oil and water pump service, thermostat checks, fuel circulation, governor and nozzle-holder service, and engine troubleshooting.

Sample Swing Bearing and Boom Drift Standards

For the North American EX50u, the dial-indicator swing bearing check uses an empty bucket. The performance table lists 0.6–0.9 mm as standard play and 2 mm as the reference limit.

The same edition lists up to 5 mm of boom cylinder drift in five minutes with a 210 kg bucket load, hydraulic oil at 50 ± 5 °C, and the engine stopped.