Part of the Hitachi Operator Manuals.
Low gear oil in a swing reduction unit or a missed greasing interval on the front pins shows up as wear you pay for in hours, and the Hitachi EX120 operator manual PDF (OEM ID EM12H-1-4) is the 138-page book that keeps those checks on schedule for this hydraulic excavator. The maintenance guide takes up about a quarter of the book and covers greasing, engine oil, gear oil, hydraulic, fuel, air intake, cooling and electrical service by interval. Hydraulic and electrical circuit layouts show where each component sits on the machine. Troubleshooting charts sort engine, control and hydraulic complaints by cause and remedy. Fill each propel reduction unit with 3.5 L of gear oil and the swing reduction unit with 3.2 L, then tighten the pilot filter element to 20-29 N·m. Guessing a final drive fill level can cost you a whole shift. Bookmarks and a searchable text layer take you straight to the interval chart you need.
What's Inside This Hitachi EX120 Operator Manual
| System | Pages | Key Topics |
|---|---|---|
| Operation Manual | 1-2 | Warranty, Machine Numbers, Directions, Safety, Measurements |
| To the Operator | 7-10 | Understand Machine Operation, Wear Protective Clothing, Precautions for Inspection |
| Name and Function of Components | 11-34 | Controls, Instrument Panel, Accelerator Lever, Starter Switch, Gauges and Indicators, Mode Selection, Auto Idling Device, Propel Levers |
| Inspect Excavator Daily Before Starting | 35-36 | Front Attachment, Arm Cylinder, Bucket Cylinder |
| Operation | 37-40 | Starting the Engine, Starting Procedure for Cold Conditions, Checking Instrument After Starting, Stopping the Engine, Warming-Up, Warming Excavator During Cold Weather |
| Basic Machine Operation | 41-50 | Move Excavator Safely, Carry Bucket Low, Avoid Tipping, Operate with Caution, Avoid Power Lines, Check Work Site, Operating in Water or Mud, Avoid Hard Digging |
| Transporting | 51-54 | Loading the Excavator, Center the Excavator on the Trailer, Dimensions for Transportation, Transportation of Long Arm Front Attachment |
| To the Mechanic | 55-56 | Warranty, Measurements |
| Safety Precautions for Mechanics | 57-60 | Understand Correct Service, Stop the Engine, Precautions for Inspection and Maintenance, Service Hydraulic System Safely, Lock the Engine Hood, Support Raised Equipment |
| Components Locations and Circuits | 61-70 | General, Hydraulic System, Electrical Circuit |
| Maintenance | 71-105 | Maintenance Guide |
| Maintenance Services Under Various Conditions | 106-108 | Storing the Excavator |
| Assembly of Front-End Attachment | 109-118 | Open Package, Check Items and Quantity, Prepare Equipment and Materials, Clean Connecting Portions, Remove Blind Plug, Mount the Boom, Connect Rod-End Side Boom Cylinder |
| Troubleshooting | 119-126 | Engine, Electrical System, Heater, Control System, Hydraulic System |
| Specifications | 127-132 | Operating Weight, Engine, Working Ranges, Shoe Types, Bucket Types |
| Handling Optional Attachments | 133-138 | Hydraulic Breaker, Hydraulic Oil Replacement, Filter Element, Pressure Release, Crusher |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Swing reduction unit gear oil capacity | 3.2 L | p. 80 |
| Propel reduction unit gear oil capacity | 3.5 L x 2 | p. 74 |
| Pilot filter element tightening torque | 20-29 N·m (2-3 kgf·m) | p. 80 |
| Low pressure hydraulic hose clamp torque | 5.9-6.9 N·m (0.6-0.7 kgf·m) | p. 87 |
| Propel reduction device plug fastening torque | 49 N·m (5 kgf·m) | p. 74 |
| Union joints of hydraulic hoses and pipings (19mm) | 29 N·m (3 kgf·m) | p. 103 |
| Union joints of hydraulic hoses and pipings (22mm) | 39 N·m (4 kgf·m) | p. 103 |
| Engine Oil Replacement Capacity | 15L | p. 78 |
| Propel Reduction Device Oil Capacity | 3.5L x 2 | p. 80 |
| Fuel Tank Capacity | 250L | p. 89 |
| Propel Reduction Device Oil Drain Plug Torque | 49 N·m | p. 80 |
| Full Flow Filter Element Bolt Fastening Torque | 49 N·m | p. 85 |
Hitachi EX120 Common Problems This Manual Covers
Hitachi EX120 all hydraulic operations lack power, with front, swing and travel functions slow and weak
Cycle every function several times if the machine sat idle a long time; air separates and collects in the cylinders (page 124). Check hydraulic oil level next. Before opening the tank to clean the suction strainer, bleed air from the oil tank to release internal pressure (page 58). Pump wear or low main relief set pressure is shop work; page 71 says never adjust that valve.
Manual Section: Hydraulic System Troubleshooting p. 124During normal digging work, hydraulic oil temperature keeps rising higher than it usually runs
Stop the engine before you touch anything, since page 57 says not to run it during service unless the procedure is approved. Clean the oil cooler and its front net of dust and debris; a dirty oil cooler is the first cause listed on page 125. Then check engine fan belt tension and adjust it if the belt is slack.
Manual Section: Hydraulic System Troubleshooting p. 125Oil leaking from a low pressure hydraulic hose connection near the clamp or suction manifold
Stop the engine and bleed air from the hydraulic oil tank to release internal pressure before touching the hose, as page 58 requires. Retighten the loosened clamp to 5.9 to 6.9 N·m following page 87. If the leak persists with the clamp at torque, the suction manifold is the next suspect on page 125; repair or replace it.
Manual Section: Hydraulic System Troubleshooting p. 125Engine coolant temperature gauge climbs too high and the overheat warning lamp comes on
Stop and let the engine cool before you open anything; page 94 warns never to remove the radiator cap while water temperature is high, because steam will blow out. Check coolant level, then clean the oil cooler front net, radiator core and oil cooler core per page 120. Tighten or replace loose fan belts and clean a plugged air cleaner. Replace a faulty radiator cap; see your HITACHI dealer for a faulty thermostat.
Manual Section: Engine Troubleshooting p. 120After control valve or swing motor replacement, swing operation is not smooth and makes abnormal noise
Run the swing slowly for about 10 minutes to work out air trapped in the swing hydraulic circuit, as page 126 describes. Check hydraulic oil tank level afterward. If roughness continues, supply grease to the swing bearing, since short grease is a listed cause. A worn swing gear or damaged swing ball bearing calls for repair or replacement.
Manual Section: Hydraulic System Troubleshooting p. 126Travel is not smooth, with the tracks running rough or dragging while propelling
Check track link tension and adjust it if the track is too tight or too loose. Inspect the front idler and rollers for oil leaks; supply oil or repair them. Stop the engine before clearing stones or foreign matter from the undercarriage, as page 57 directs. If travel still drags, a dragging parking brake or bent track frame needs repair (page 125).
Manual Section: Hydraulic System Troubleshooting p. 125Frequently Asked Questions
What are the replacement specs for the hydraulic return and full-flow filter elements on the Hitachi EX120?
The full-flow filter element should be replaced every 500 hours. When using a hydraulic breaker, the replacement interval for the full-flow filter element is reduced to 100 hours. p. 134
What are the replacement specs for engine oil, fuel, and air filters on the Hitachi EX120?
The engine oil filter should be replaced every 250 hours. The fuel filter should be replaced every 500 hours. The air cleaner outer element should be cleaned every 250 hours or when the warning lamp lights, and replaced after cleaning 6 times or 1 year. p. 72
What is the correct tightening torque for the swing unit mounting bolts on the Hitachi EX120?
The bolts fixing the swing unit must be tightened to a torque of 539 N-m (55 kgf-m). p. 102
How do I adjust the track link tension?
Jack up the machine and measure the distance between the upper surface of the shoe and the lower surface of the side frame at the center. The distance should be 260-270 mm for general ground, 340 mm for gravel, and 270-340 mm for damp ground. p. 100
What is the procedure for draining the hydraulic oil tank?
After leaving the machine in a standstill state for a prolonged time to bleed air, slowly open the drain plug on the tank bottom to drain water and sediments. CAUTION: If this is done immediately after operation, high-temperature hydraulic oil may blow out and cause injury. p. 82
Is this Hitachi EX120 Operator Manual a digital download?
Straight to your device: 138 pages of searchable Operator Manual, downloadable the moment payment goes through.
Can I print this Hitachi EX120 manual?
Yes. Print the pages or sections you need for your own shop use. Any standard printer works.
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