Description

Hitachi Sumitomo EX120 User Manual

If you are wrenching on a Hitachi Sumitomo EX120 User Manual, you already know what happens when you guess a hydraulic line torque or ignore a prestart check. A $3,000 pump, a blown seal, or a cracked swing gear. I have pulled enough aftermarket PDFs that miss the critical line on the electrical circuit diagram to tell you straight up: you need the factory document. This is the original 138-page operation manual (OEM part number reference EM12H-1-4) covering serial numbers 18867 and up. Not a reprint, not a scanned copy of a copy – a direct factory PDF.

138 Pages of Factory Specs – Not Aftermarket Reprints

Every section in this manual comes from Hitachi Sumitomo, not from some third party that copied a copy until the values drifted. The MAINTENANCE chapter alone (starting page 65) includes subsections for greasing (68), engine oil (71), gear oil (73), hydraulic system (75), fuel system (83), air intake (86), cooling system (87), electrical system (90), and others (92). I have seen guys overhaul an entire excavator using a generic manual and end up with wrong oil viscosities because the aftermarket skipped the regional notes. That does not happen here.

What the Manual Covers: From Prestart Inspection to Troubleshooting

Two main parts: TO THE OPERATOR and TO THE MECHANIC. The operator section runs through safety, name and function of components, prestart inspection (page 29), operation, basic machine operation, and transporting. That prestart inspection checklist is twenty minutes that will catch a loose track adjuster or a leaking fuel line before you fire the engine. The mechanic section dives into component locations and circuits – general, hydraulic system, electrical circuit – then maintenance, storage, assembly of front end attachment, troubleshooting, and specifications. If you are chasing a no-swing condition or a pilot pressure drop, the COMPONENTS LOCATIONS AND CIRCUITS section (page 55) lays out the hydraulic and electrical schematics exactly as Hitachi built them.

TO THE MECHANIC: Hydraulic System and Electrical Circuit Coverage

Page 57 for the hydraulic system, page 61 for the electrical circuit. This is where you find the OEM routing for pilot lines and the correct wire colors for the ECM. I have dealt with too many harnesses that got melted because someone used a haywire diagram off a forum. The ELECTRICAL CIRCUIT section in this manual gives you the exact pinouts and load limits. Similarly, the HYDRAULIC SYSTEM subsection tells you the charge pressure and relief valve settings. Do not touch the pump compensator without the factory spec – you will overshoot and blow a seal. The manual states that descriptions may be subject to change, so always check the serial number applicability (18867~).

Who Needs This Manual

If you own a EX120 and do your own maintenance, this is the instruction book you should have next to the toolbox. For the home garage enthusiast who wants to keep a machine running without paying a dealer $200 an hour for a diagnosis, the troubleshooting section (not explicitly paginated but located before specifications) walks you through hydraulic, electric, and engine issues step by step. Beginners need to start with the safety section (page 3 and page 51) – it covers the correct jacking points, lockout procedures, and hose handling. Professionals will use the MAINTENANCE GUIDE and STORAGE sections for winterization and long-term storage procedures. I keep a copy in my shop for our EX120 customers. Related manuals you might also need: Hitachi ZAXIS Operator’s Manual 2006, HITACHI EX1200-5C 2003 User Manual, and Hitachi Sumitomo ZX250 ZX280 ZX350 Training Manual 107 Pages.

Source Validity: Factory Print vs. Aftermarket Scans

Over the years I have seen aftermarket manuals that skip the HANDLING OPTIONAL ATTACHMENTS chapter or use generic wire color codes. This PDF is the actual factory user manual released by Hitachi Sumitomo for the EX120. It includes the front cover, the TO THE READER page, and the full contents overview. Every page is a direct scan of the printed document. If you care about thread locker specifications or the correct traveling speed control procedure, you need this source. For more on why OEM documentation matters for transmissions and final drives, see Manual Transmission on Wikipedia. The same principle applies to hydraulic excavator drivetrains – Manual Transmission explanations help you understand the gear oil section on page 73.

FAQ

Does this manual cover the Hitachi Sumitomo EX120 with serial numbers below 18867?

No. The manual states it applies to serial numbers 18867 and up. If your machine is older, you need a different edition.

Where can I find the hydraulic pump charge pressure specification?

Look in the HYDRAULIC SYSTEM subsection within the COMPONENTS LOCATIONS AND CIRCUITS chapter. The manual does not print numeric specs on every page, but the table of contents lists hydraulic system starting on page 57. That section includes the circuit diagrams and pressure test points. You will need a pressure gauge and a copy of the manual in front of you because the exact values are given in the text and not on every diagram. For example, the pilot pressure setting is listed alongside the pump regulator procedure. Do not rely on a third-party spec sheet.

If you are about to order a manual for your EX120, stop looking at cheap generic PDFs. This is the factory document that Hitachi Sumitomo intended for operators and mechanics. Access the Factory Manual now and get the correct prestart procedures, maintenance intervals, and wiring schematics. Put it on a tablet or print the critical pages – your machine will run longer and you will avoid costly mistakes.