Komatsu PC128US-2, PC138US-2, PC138USLC-2E0 2007 Workshop Manual

You have a Komatsu excavator that is not tracking straight, or the hydraulics are sluggish. You pull out a generic aftermarket manual and find torque specs that don’t match the bolt you are holding. That is a waste of billable time and a safety hazard. The Komatsu PC128US-2, PC138US-2, PC138USLC-2E0 2007 Workshop Manual from AutoRepairManuals gives you the factory data you need to get the job done right the first time. No guesswork, no reprints—just the original OEM material.

7 Major Sections Covering Every Component

This manual is split into seven logical sections: GENERAL, STRUCTURE AND FUNCTION, TESTING AND ADJUSTING, DISASSEMBLY AND ASSEMBLY, MAINTENANCE STANDARD, and OTHERS. Each section follows the same format Komatsu used at the factory. You get the exact procedures for the PC128US-2, PC138US-2, and PC138USLC-2E0 models, with serial number splits (5001-7730 for 128US-2, 7731 and up for Galaxy, etc.). The manual is 1029 pages thick, so nothing is left out.

Testing and Adjusting: Your First Step to Accurate Diagnosis

Section 20 – TESTING AND ADJUSTING is where most techs start. It begins with the STANDARD VALUE TABLE for engine, chassis, and electrical parts. Need to know the proper valve clearance? It is on the table. Want to measure blow-by pressure or adjust fuel injection timing? The procedure is spelled out with required tools. For hydraulic work, the manual includes testing and adjusting of PC valve output pressure, LS valve differential pressure, and control circuit oil pressure. Page 20-1 gives you the standard value table for engine. Do not waste time hunting for numbers; they are all there.

How to Read the Shop Manual: It Matters

The FOREWORD section covers how to use this manual. It includes hoisting instructions, method of disassembling and connecting push-pull type couplers, coating materials, and electric wire codes. Pay attention to the safety warnings in the hoisting instructions – lifting an excavator component wrong can kill you. The manual also includes a conversion table for units, so you can work in imperial or metric. This is not a general repair guide; it is the same document Komatsu issued to dealers.

Standard Tightening Torque – Why You Cannot Skip It

Torque is not a suggestion. The STANDARD TIGHTENING TORQUE table in the foreword gives you the factory spec for every common bolt size and grade used on these machines. I have seen too many beginners strip a swing motor bolt because they thought “tight enough” was fine. With this manual, you get the exact ft-lb value. For critical fasteners like the travel motor or swing circle bolts, the torque data in the DISASSEMBLY AND ASSEMBLY section (Section 30) is non-negotiable. Use a calibrated wrench. Every time.

Foreword and Hoisting Instructions: Safety First

Hoisting instructions are not filler. The manual tells you exactly how to lift the engine, hydraulic pump, or swing assembly without damaging components or injuring yourself. It even covers how to handle the push-pull coupler if your machine is equipped. The safety warnings are written for the shop floor, not a lawyer’s office. Follow them. Also, the LIST OF LUBRICANTS AND WATER in section 01 tells you which fluids to use and capacities. Do not guess.

For the DIY mechanic who owns one of these excavators, this manual pays for itself the first time you replace a hydraulic line. Compare it to the cost of a dealer visit. Professional shops need the original OEM data to avoid liability. This is the real thing.

Related manuals you might need: Komatsu PC128US-2 PC138US-2 Shop Manual, Komatsu WA65-5 WA70-5 WA80-5 2005 Workshop Manual, Komatsu WH609-1E0 WH613-1E0 WH713-1E0 WH714H-1E0 WH716-1E0 Workshop Manual. For general knowledge on how Manual Transmission work, check external resources, but for your Komatsu, stick to this manual. Another helpful external topic is Manual Transmission theory, but again, the factory data is your authority.

What serial numbers does this manual cover?

PC128US-2 5001-7730 and 7731 & up; PC138US-2 4501 & up; PC138USLC-2E0 1001 & up.

Is this a reprint or a copy?

It is the original OEM 2007 Komatsu publication, not an aftermarket reproduction. Page 1 shows the Komatsu America Corp. copyright notice. You get the exact factory document.

Where do I find the hydraulic pressure test specs?

Section 20 – TESTING AND ADJUSTING has all standard value tables for chassis and hydraulic circuits. Specifically, the TESTING AND ADJUSTING HYDRAULIC PRESSURE IN WORK EQUIPMENT, SWING, TRAVEL CIRCUIT procedure gives you the required pressures and adjustment steps.

Does it include wiring diagrams?

Yes, the troubleshooting section includes connector arrangement diagrams, connection tables, and electrical circuit diagrams for the E-mode system. The manual covers both serial number ranges with separate diagnostic procedures.

You need factory torque specs, assembly sequences, and correct fluid capacities for your Komatsu. Do not rely on third-party data. Download the Factory Manual now and keep your excavator running to Komatsu standards.

You’ve got a Komatsu PC128US-2, PC138US-2, or PC138USLC-2E0 in the bay. Hydraulics acting up? Engine losing power? Without the factory Workshop Manual you’re guessing – and that costs money. I’ve torqued enough head bolts to know that one wrong spec turns a repair into a rebuild. This 2007 manual gives you the exact numbers Komatsu built into these machines. 1029 pages of procedures, not theory. Let’s get into what matters.

Standard Tightening Torque: Why You Need the Factory Numbers

Every bolt on an excavator has a torque range. The foreword of this manual includes a STANDARD TIGHTENING TORQUE table – not generic values from some internet forum. For the PC128US-2 and PC138US-2, you get the bolt size, grade, and torque in both foot-pounds and Newton-meters. The manual also provides a CONVERSION TABLE so you can switch between metric and imperial without rounding errors. I’ve seen guys snap M16 bolts because they used a car engine spec. Don’t be that guy. Use the factory torque.

Testing and Adjusting: The 40-Page Section That Saves You from Replacing Parts

Section 20, TESTING AND ADJUSTING, covers over 40 pages of diagnostic procedures. You get step-by-step instructions for measuring engine speed, blow-by pressure, valve clearance, and fuel injection timing. There’s a dedicated STANDARD VALUE TABLE FOR ENGINE and for CHASSIS and ELECTRICAL PARTS. Need to adjust the LS valve output pressure? The manual walks you through the test points and required tools. It even includes a PM CLINIC INSPECTION TABLE – that’s the preventive maintenance schedule. No fluff, just the numbers you need to decide whether to adjust or replace. And they list the specific tool numbers – you won’t wonder whether a 14mm hex works when they call for a 17mm.

What Does This Workshop Manual Cover for the PC128US-2 and PC138US-2?

This Workshop Manual covers all serial number ranges: PC128US-2 from 5001 up, PC138US-2 from 4501 up, and PC138USLC-2E0 from 1001 up. That includes both the Avance and Galeo series. The table of contents shows six main sections: 01 GENERAL (specs, weights, lubricants), 10 STRUCTURE AND FUNCTION (every subsystem from PTO to monitor), 20 TESTING AND ADJUSTING, 30 DISASSEMBLY AND ASSEMBLY, 40 MAINTENANCE STANDARD, and 90 OTHERS. Each section is numbered and cross-referenced. You don’t flip through 1000 pages blind – the bookmarks in the PDF let you jump to the exact procedure.

7 Systems Covered in the Structure and Function Section

Section 10 breaks down every major system: PTO, Radiator and Oil Cooler, Power Train, Swing Circle, Swing Machinery, Track Frame, Idler Cushion. It also covers hydraulic component layout, the CLSS system, travel motor (final drive), swing motor, solenoid valve, PPC accumulator, and the hydraulic drift prevention valves. For each subsystem, the manual explains the function and provides sectional views. You don’t need to guess which valve does what – it’s all there. This is the kind of detail that prevents you from disassembling the wrong side of the control valve.

Why Aftermarket Manuals Don’t Cut It for Komatsu Gear

I’ve seen cheap reprints and PDFs that claim to be factory but use generic wiring diagrams. This manual is an original Komatsu publication printed in 2007. It includes the QR code and proprietary marking – no third-party copies. The ELECTRIC WIRE CODE section uses the actual Komatsu wire color codes, not a translation of JIS. If you’re working on a PC128US-2 hydraulic drift issue, you need the factory procedure for checking the arm drift prevention valve. Aftermarket manuals skip those sub-sections. You can read about Manual Transmission basics online, but for Komatsu hydraulic systems, stick to OEM. The same goes for the Manual Transmission – though that’s a different context – the point is: use the right documentation.

Related manuals you might need:

• Komatsu PC128US-2 PC138US-2 Shop Manual
• Komatsu PC128US-2 / PC138US-2 Shop Manual – Section: Section 30 Disassembly And
• Komatsu WA65-5 WA70-5 WA80-5 2005 Workshop Manual

Does this manual include torque specifications for the swing motor?

Yes. The STANDARD TIGHTENING TORQUE table covers all major fasteners. For swing motor specific bolts, refer to the assembly section which references those values.

Can I use this manual for a PC138US-2 with serial number 7731?

Yes. The manual covers serial numbers 5001-7730 and 7731 and up for the PC128US-2, and 4501 and up for PC138US-2. Check the serial number prefix – it’s included.

Does the manual have wiring diagrams?

Yes. Section 10 includes ELECTRIC COMPONENT LAYOUT and ELECTRIC CONTROL SYSTEM. The troubleshooting section provides connector arrangement diagrams and connector pin connection tables.

What tools do I need for the testing procedures?

The manual lists required tools in TOOLS FOR TESTING, ADJUSTING AND TROUBLESHOOTING. It specifies part numbers for pressure gauges, tachometers, and adapters.

You’ve got a Komatsu machine that deserves factory specs. This Workshop Manual weighs in at 1029 pages – every one of them written for technicians who need to get it right the first time. If you’re rebuilding the travel motor or adjusting the track tension, you need the Torque values and clearances from the factory. Download the Factory Manual now – your torque wrench is waiting.