Part of the Hitachi Repair Manuals.
Need factory data for your Hitachi EX200-5 or EX120-5? This 914-page Hitachi EX200-5, EX120-5 Technical Manual PDF (OEM #TT155E-02) covers both hydraulic excavators from the swing bearing to the injection pump. You get complete electrical circuit diagrams with connector and harness layouts, hydraulic schematics for the pump device, control valve, and travel system, plus a massive troubleshooting section that walks each fault from symptom to root cause. Engine work is covered too: cylinder head, crankshaft, turbocharger, and injection pump calibration data. Set valve clearance at 0.40 mm cold, then torque the rocker arm lock nuts to 25.5 N-m; cylinder head bolts go to 7.0 to 9.0 kg-m followed by an angular tightening of 90-120 degrees. No more chasing electrical gremlins with a test light and a hunch. Bookmarked with a full text layer: search any spec, jump to any system, and get back on the machine.
What's Inside This Hitachi EX120-5 Manual
| System | Pages | Key Topics |
|---|---|---|
| Electrical Circuit Diagrams and Harnesses | 1-10 | Wiring Diagrams, Connector Layouts, engine/cab/relay and A/C Harnesses, Key Switches, Controllers, Sensors and Relays |
| Technical Manual Introduction | 11-13 | Operational Principle, Troubleshooting Method, How to Use the Workshop Manual |
| Safety | 14-39 | Emergency Procedures, Protective Equipment, Safe Operation and Maintenance Practices |
| General | 40-55 | Specifications, Working Ranges, Machine Dimensions, Component Weights |
| System Operation | 56-89 | Control System, Hydraulic System and Electrical System Operation |
| Component Operation | 90-165 | Pump Device, Swing Device, Control Valve, Pilot Valve and Travel Component Operation |
| Operational Performance Test | 166-221 | Engine Test, Excavator Test, Component Test and Performance Standards |
| Troubleshooting | 222-707 | Diagnosing Procedures, Symptom-Based Troubleshooting, Electrical and Hydraulic Fault Finding |
| Engine General and Maintenance | 708-757 | Engine Repair Instructions, Main Data and Specifications, lubricating/fuel/cooling Maintenance |
| Engine Assembly | 758-828 | External Parts and Major Component Disassembly and Reassembly Steps |
| Engine Subsystems | 829-862 | Lubricating System, Cooling System, Fuel System and Turbocharger Service |
| Engine Electricals and Accessories | 863-902 | Air Compressor, Starter Motor and Engine Electrical Components |
| Reference | 903-914 | Special Tool List and Unit Conversion Tables |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| All Models | ||
| Valve clearance (inlet/exhaust) | 0.4/0.4 mm | p. 45 |
| Intake valve clearance | 0.40 mm (0.0157 in) | p. 174 |
| Rocker arm adjusting screw lock nut torque | 25.5±4.9 N⋅m (2.6±0.5 kgf⋅m, 18.8±3.6 lbf⋅ft) | p. 174 |
| Cylinder head bolt torque | 7.0-9.0 kg·m (50.6-65.1 lb.ft) | p. 730 |
| Valve Clearance (Intake/Exhaust) | 0.40 mm | p. 174 |
| Swing Device Gear Oil Capacity | 6.4 L | p. 508 |
| Travel Device Gear Oil Capacity | 3.5 L | p. 598 |
| Lower Roller Weight | 20 kg | p. 656 |
| EX120-5 | ||
| Engine Rated Output | 63 kW | p. 42 |
| Swing Speed | 12.7 rpm | p. 42 |
| Main Relief Pressure | 34.3 MPa | p. 47 |
| A-4BG1PG | ||
| Engine Oil Capacity | 13.2 L | p. 47 |
Hitachi EX120-5 Common Problems This Manual Covers
Hitachi EX120-5 boom and arm cylinders weak, bucket stalls in the pile, all functions slow when oil warms
Test main relief pressure at the pump port with hydraulic oil at operating temperature and engine at full throttle. On the EX120-5, relief should hold 34.3 MPa; the spec is on page 47. If pressure falls short, adjust or replace the main relief valve, then repeat the cylinder speed tests before returning the machine to work.
Manual Section: Front Attachment Control System TroubleshootingEngine hard to start cold, runs rough at low idle, down on power under load
Check valve clearance first on a cold engine; intake and exhaust are both 0.40 mm, listed on page 174. Adjust each rocker screw, then torque the lock nuts to 25.5 N·m. If starting stays hard, move to the fuel side and inspect the injection nozzles covered in the Fuel System section on page 843.
Manual Section: Maintenance p. 174Swing speed slow in both directions, grinding noise from swing device while slewing a loaded bucket
Check the swing device gear oil level and condition before pulling the motor. Drain and refill with 6.4 L of gear oil; the capacity is listed on page 508. If oil comes out with metal flakes, run the swing troubleshooting checks, then measure swing relief pressure per the Operational Performance Test section on page 166.
Manual Section: Swing System Troubleshooting p. 508Machine pulls to one side during travel, one track turns noticeably slower than the other
Verify track sag on both sides first; a tight track drags and mimics a drive problem. Drain each travel device and refill with 3.5 L of gear oil, capacity shown on page 598. If the machine still mistracks, swap travel lines side to side to isolate the motor from the control valve.
Manual Section: Travel System Troubleshooting p. 598Engine oil leaking around the oil pan after a service, oil level drops between daily checks
Clean the pan rail and drain plug area, then run the engine and find the actual leak path before pulling parts. Retorque the drain plug to 7-9 kg·m (51-65 lb.ft), spec on page 732. If the pan gasket weeps, replace it following the Engine Assembly procedures starting on page 758.
Manual Section: General Information p. 732Frequently Asked Questions
What are the torque specifications for the pump device mounting bolts on the EX120-5?
The pump device mounting bolts for the EX120-5 should be tightened to a torque of 49 N⋅m (5 kgf⋅m, 36 lbf⋅ft). This is specified in the tightening torque table for the machine. p. 393
How do I adjust the valve clearance for the 4BG1 engine?
The standard valve clearance for both intake and exhaust valves on the 4BG1 engine is 0.40 mm (0.016 in) when the engine is cold. Adjust the clearance by loosening the adjusting screw lock nuts on the rocker arms and using a thickness gauge to set the gap. p. 779
What is the standard compression pressure for the 4BG1 and 6BG1 engines?
The standard compression pressure for these engines is 31.0 kg/cm² (441 psi) at 200 rpm at sea level. If the measured value exceeds the specified limit, the related parts must be checked. p. 754
What is the procedure for bleeding air from the hydraulic pump?
To bleed air from the hydraulic pump, remove the air bleeding plug from the top of the pump and fill the pump housing with hydraulic oil. After filling, temporarily tighten the plug, start the engine at slow idle, slightly loosen the plug until oil oozes out, and then securely tighten the plug. p. 390
What is the tightening torque for the main bearing cap bolts on the engine?
The main bearing cap bolts for the engine should be tightened to a torque of 23.0–25.0 kg⋅m (166–181 lb⋅ft). Ensure the crankshaft turns smoothly by manually rotating it after tightening. p. 813
What format is this Hitachi EX200-5, EX120-5 manual in?
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