Description

Komatsu PC138US-8, PC138USLC-8 Workshop Manual

You have a Komatsu PC138US-8 or PC138USLC-8 on your lot with a hydraulic leak, a code on the monitor, or a swing motor that won’t hold. The aftermarket manuals you find online are full of generic diagrams and torque values that don’t match what Komatsu stamped on the parts. That costs you billable hours and blown seals. This OEM workshop manual is printed from the same source your dealer uses. 997 pages of factory procedures, not a third-party rewrite. If you’ve ever torqued a head bolt to the wrong spec because some website said “35-40 ft-lbs” when Komatsu calls for 58 ft-lbs, you’ll appreciate what’s in this binder.

Engine and Cooling System: Factory Mount and PTO Specs

Section 10 starts with the engine mount, PTO, and cooling system. You get the exact bolt pattern for the PTO housing and the torque sequence for the flywheel housing bolts. The coolant capacity table lists the mixture ratio for the San Antonio heat. Page 1 of the manual shows the serial number range: PC138US-8 20001 and up, PC138USLC-8 20001 and up. That’s the first thing I check before ordering parts. Cooling system bleed procedures are documented step-by-step, including the air bleed valve location and required tool list. No guesswork.

Testing and Adjusting: 100+ Pages of Pressure Checks and Valve Clearance

Section 30 is where the manual earns its keep. Tools for testing—listed with part numbers and sketches of the special tools you’ll need. Testing engine speed, exhaust temperature, blow-by pressure, oil pressure. The fuel system section covers residual pressure release from the fuel circuit, fuel pressure testing, and return rate checks. Adjusting valve clearance is on the list with the feeler gauge sizes and cold-engine specs. Hydraulic system pressure tests for the work equipment, swing, and travel circuits are spelled out with the port locations and expected readings. Pump PC control circuit pressure? It’s in there. So is the LS control circuit. And the solenoid valve output pressure. If you’re chasing a travel deviation, there’s a procedure for that too. Komatsu PC138US-8, PC138USLC-8 Workshop Manual – 946 Pages of OEM Specs

Standard Value Tables: Chassis and Engine Wear Limits

Section 20 gives you the standard service value tables for engine-related parts and chassis-related parts. Piston ring gap limits, cylinder bore wear, idler clearance, track roller rebuild specs. You don’t get these from a Chinese PDF. These are the numbers Komatsu factory technicians use during PM clinic service. Page 3 of the manual lists the Form Number SEN01977-12—that’s the exact revision for this machine family. Cross-reference anything you need from the table of contents starting at page 4.

Troubleshooting: Failure Codes and Fuse Locations

Section 40 is the troubleshooting chapter. Failure code table covers every diagnostic code the ECM throws. Fuse locations with amperage ratings. The manual walks you through the sequence of events in troubleshooting and the checks you should make before you start swapping parts. There’s a classification table that sorts codes by system—engine, hydraulic, electrical. If you’ve ever spent an afternoon chasing an intermittent fault that turned out to be a loose ground at the solenoid valve connector, you know why this matters. The electrical system chapter covers the monitor system, KOMTRAX, and each sensor with pin-out diagrams. Komatsu PC138US-8 PC138USLC-8 2000 Operators Manual – Factory Specs

Source Authenticity: OEM vs Aftermarket

Aftermarket manuals often skip the safety notices. This workshop manual includes a section called “Safety Notice” that lists the specific hazards—pinch points, high-pressure fluid injection, battery explosion risks. The standard tightening torque table is a full-page chart with bolt grade, thread size, and wet/dry torque values. You won’t find that in a third-party reprint. The manual is built around the actual hydraulic system layout, with part numbers for the valve control arm, CLSS circuit, and the multi-control valve. If you’re swapping a swing motor, the disassembly and assembly procedure includes the exact shim thickness for bearing preload. Komatsu WA65-5 WA70-5 WA80-5 2005 Workshop Manual

7 Systems Covered: One Manual, Full Coverage

The table of contents breaks down seven major systems: engine and cooling, power train (swing circle and machinery), undercarriage (idler, rollers, sprocket, track shoe), hydraulic system in three parts, work equipment (cylinders), cab and air conditioner, and the full electrical system. Each section has its own index. You can flip directly to the hydraulic cylinder section to get the dimensions of components and the holding valve procedure. The PPC valve adjustment section tells you the angle of the lever and the feeler gauge for the play. This is the level of detail that keeps you from snapping a bolt.

Does This Cover the Fuel System and Hydraulic Drift?

Yes. The testing section includes “Checking parts which cause hydraulic drift of work equipment”—a procedure that isolates cylinder drift from valve spool leakage. The fuel circuit section shows how to bleed air, test fuel return rate, and check for leakage at the injection pump. The manual also covers the KOMTRAX system, which sends telemetry data—useful if you’re troubleshooting a loss of communication with the dash monitor. For general knowledge on manual transmission systems, see Manual Transmission. Another external reference on manual transmission basics is Manual Transmission.

What makes this manual better than a PDF I can access for free?

Free PDFs are usually scanned copies of an old dealer manual with missing pages, illegible torque charts, and no revision updates. This is a clean OEM file with all 997 pages intact, including the KOMTRAX system and PM clinic service procedures that most pirated copies skip. If you price your time at shop rate, the cost of this manual pays for itself on one avoided misdiagnosis.

Can I use this on the PC138USLC-8 with a different serial number?

Yes. The manual covers both the PC138US-8 and PC138USLC-8 starting at serial 20001.

You have a Komatsu excavator that needs work. You can either guess the torque, risk a leak, and waste three hours decompressing the hydraulic system because you used the wrong sequence—or you can own the printed factory procedure. Access the Factory Manual and put it on your bench next to your torque wrench.