Part of the Hitachi Repair Manuals.
This 467-page Hitachi EX40u, EX50u, 50u Technical Manual puts the complete factory reference for these excavators in your hands, from main pump teardown to final engine reassembly. You get full wiring diagrams covering the main harness, engine harness, and air conditioner circuits, plus hydraulic schematics for the main and pilot circuits, a dedicated troubleshooting section for actuator and swing system faults, and page after page of torque specs and clearance charts. Torque the delivery valve holder to 39 to 44 N-m, and keep swing motor drainage under 0.5 L/min at constant max speed; anything higher and you're chasing a worn valve. No more flipping between three dog-eared photocopies trying to find the right circuit. Bookmarked by group and searchable by keyword, this PDF opens on your phone or tablet right at the machine, so you can confirm the spec before you pull a single fitting.
What's Inside This Hitachi EX40U, EX50U Manual
| System | Pages | Key Topics |
|---|---|---|
| General | 2-17 | Specifications, Working Ranges, Engine Specification, Main Component, Electrical System, Monitor and Switches |
| System | 18-27 | Hydraulic System Outline, Main Circuit, Pilot Circuit |
| Component Operation | 28-73 | Main Pump, Swing Motor, Control Valve, Pilot Valve, Travel Motor, Center Joint |
| Operational Performance Test | 74-117 | Engine Speed, Engine Compression Pressure, Travel Speed, Swing Speed, Hydraulic Cylinder Cycle Time, Main Relief Valve Set Pressure |
| Troubleshooting | 118-169 | Diagnosing Procedure, Engine System Troubleshooting, Actuator Operating System Troubleshooting, Front Attachment System Troubleshooting, Swing System Troubleshooting |
| All Diagrams | 170-180 | Hydraulic Circuit, Main Harness, Air Conditioner Harness, Electrical Circuit, Engine Harness, Frame Harness |
| General Information | 181-195 | Precautions for Disassembling and Assembling, Tightening Torque Specification, Torque Chart, Piping Joint |
| Upperstructure | 196-269 | Canopy, Counterweight, Pump Device, Control Valve, Swing Device, Pilot Valve |
| Undercarriage | 270-313 | Swing Bearing, Travel Device, Center Joint, Track Adjuster, Front Idler, Track |
| Front Attachment | 314-345 | Cylinders, Boom and Arm Cylinders, Bucket, Swing and Blade Cylinders, Maintenance Standards |
| Engine | 346-467 | General Information, Engine Disassembly, Inspection and Repair, Reassembly, Lubrication System, Cooling System, Fuel System, Troubleshooting |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Tightening Torque: delivery valve holder | 39 to 44 N·m (4 to 4.5 kgf·m, 29 to 33 lbf·ft) | p. 83 |
| Pilot Filter Hose | UNF9/16 | p. 100 |
| TRAVEL MOTOR LEAKAGE | 60 or less | p. 112 |
| SWING MOTOR DRAINAGE at constant maximum speed | (0.5 or less) | p. 113 |
| SWING MOTOR DRAINAGE with the motor relieved | (7 or less) | p. 113 |
| Engine oil pressure indicator comes on when pressure is below | 0.5±0.1 kgf/cm² | p. 152 |
| Overheat indicator comes on when coolant temperature is above | 110±3 °C (230±37 °F) | p. 153 |
| Engine cushion rubber mounting nut torque | 137 N·m (14 kgf·m, 101 lbf·ft) | p. 189 |
Hitachi EX40U, EX50U Common Problems This Manual Covers
Hitachi EX40u hydraulic fluid leaking from union joints after pump replacement or routine service.
Inspect the union joints and replace any damaged O-rings. Coat new seals with grease before assembly. Torque the 22mm wrench hydraulic hoses to 39 N·m (4 kgf·m) as specified on page 205. Do not overtighten the nut to avoid cracking the adaptor.
Manual Section: Upperstructure p. 205Engine turns over but refuses to start after storage or filter changes in cold weather.
Check the fuel pump for air mixture and verify the engine oil pressure indicator operates at 0.5±0.1 kgf/cm² as shown on page 152. Retighten connections, replace damaged packing, and bleed air from the fuel lines. Test the battery voltage and wiring harness continuity.
Manual Section: Engine System Troubleshooting p. 152Sluggish arm and bucket movement with loud pump whine after complete hydraulic system rebuild.
Remove the top air bleeding plug and fill the housing with hydraulic oil. Follow the procedure on page 184 to run the engine at slow idle. Loosen the plug to bleed air until oil oozes. Verify primary pilot pressure reaches 40±5 kgf/cm² to ensure complete system bleeding.
Manual Section: General Information p. 184Excavator mistracks to one side or travel speed lacks power during heavy load operation.
Test the main relief valve set pressure at the pump. Adjust the P1 and P2 relief valves to maintain 260±10 kgf/cm² as detailed on page 113. Drain the travel motor case and refill it with fresh hydraulic oil before retesting the track tracking speed.
Manual Section: Operational Performance Test p. 113Frequently Asked Questions
What are the torque specifications for the Hitachi EX40U swing reduction gear ring gear bolts?
When installing the ring gear (18) into the housing (23) for the swing reduction gear, tighten the 8 mm socket bolts (17) to a torque of 69 N·m (7 kgf·m, 51 lbf·ft). This ensures proper assembly of the swing device. p. 244
What are the torque specifications for the Hitachi EX50U engine mounting bolts?
For engine cushion rubber mounting nuts and front engine bracket mounting bolts (14 mm bolt dia), the torque is 137 N·m (14 kgf·m, 101 lbf·ft). Rear engine bracket mounting bolts (10 mm bolt dia) require a torque of 49 N·m (5 kgf·m, 36 lbf·ft). p. 187
What are the general replacement guidelines for O-rings and sealing kits?
It is important to always replace O-rings, backup rings, and oil seals with new ones after removal. Before assembly, coat these new components with grease to ensure proper sealing and prevent damage. p. 183
What is the standard valve clearance for the engine's intake and exhaust valves?
The standard valve clearance for both intake and exhaust valves is 0.4 mm. This measurement should be performed when the engine is cold to ensure accuracy. p. 80
What is the standard primary pilot pressure for the hydraulic system?
The standard primary pilot pressure is 40±5 kgf/cm². This measurement should be taken without load, with the engine running at fast-idle speed, and the hydraulic oil temperature maintained at 50±5 °C (122±9 °F). p. 113
Is this Hitachi EX40U, EX50U Technical Manual a digital download?
Instant PDF download. You get the full 467-page searchable Technical Manual immediately after payment. Open it on your laptop, tablet, or phone right in the shop.
Can I print this Hitachi EX40U, EX50U manual?
Yes. The PDF has no DRM restrictions, so print any page or section you need for your shop. Works with any standard printer.
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