Description

Komatsu PC100-5, PC120-5, PC120-5 MIGHTY 1992 Workshop Manual

If you’ve ever tried rebuilding a Komatsu excavator with a third-party manual that says “tighten until snug” and doesn’t list a single ft-lb number, you know the headache I’m talking about. I’ve seen guys strip valve covers, mis-time injection pumps, and chase electrical ghosts because the aftermarket book left out half the diagnostic flowcharts. This 1992 OEM Komatsu workshop manual – for the PC100-5, PC120-5, and PC120-5 MIGHTY – is the real deal. 644 pages of factory procedures, torque specs, and circuit diagrams that someone actually tested on the machine.

Engine and Fuel System Coverage

The S4D95L-1 engine lives in these machines, and this manual pulls no punches. You get the full breakdown of engine-related parts, the mount system, and the fuel system – from the injection pump to the governor motor. Want to adjust valve clearance? Section 20 (Testing and Adjusting) gives you the step-by-step: loosen the locknut, set the feeler gauge, torque to spec. No guesswork. The fuel injection timing procedure includes the exact dial indicator setup and the travel for the governor motor lever. Aftermarket manuals love to skip this – and then you get a cold-start nightmare. Here it’s all laid out.

Does This Manual Cover the PEMC System and EMACC?

Yes, and thank somebody for that. The Engine Control System, PEMC system, and the EMACC (Electronic Monitor and Control Console) are documented with actual wiring diagrams and connector pinouts. If you’re getting a self-diagnostic code like E-3 (abnormality in battery relay) or C-2 (short circuit in straight-travel solenoid), the troubleshooting charts in the back of Section 20 walk you through the test points. No guessing where to put your multimeter probes. The manual tells you which connector, which pin, and what voltage you should see.

7 Major Systems Detailed in the Structure and Function Section

Section 10 alone covers the power train, final drive, swing circle, track frame, idler and cushion, carrier roller, and track shoe. That’s only the first half. Then it dives into the hydraulic piping, the OLSS (Open Center Load Sensing System), the L.H. 6‑spool and R.H. 5‑spool control valves, the swing motor, travel motor, PPC valve, accumulator, safety lock valve, shuttle valve, boom holding valve, and every hydraulic cylinder. You get cross-section drawings, flow paths, and pressure test points. If you’re chasing a drift in the boom or a slow swing, this is where you start.

Get the Right Valve Clearance Specs

Don’t rely on a generic diesel engine spec. The Komatsu manual lists the exact valve clearance for the S4D95L-1: intake and exhaust. It also includes the measuring compression pressure procedure – page references in the Table of Judgement Standard Values tell you what psi is acceptable and when to pull the head. I’ve seen too many guys skip this step and wonder why the engine won’t idle. The manual also covers testing the PPC output pressure, adjusting the PPC valve, and bleeding air from the hydraulic circuit. These are not optional steps; they’re how the factory says to do it.

Testing Hydraulic Pressure: Factory Procedure

Section 20 devotes multiple sub-sections to testing and adjusting hydraulic pressure in the work equipment, swing, and travel circuits. You get the charging pump pressure spec, the main pump control pressure, and the stroke measurement for the servo piston. The tools list on the tools-for-testing page tells you exactly which gauges and adaptors you need – part numbers included. No “use a pressure tester” vague language. This is how you diagnose a weak pump or a stuck spool without throwing parts at it.

Source Authenticity: Why OEM Beats Aftermarket

I’ve worked with both. Aftermarket manuals condense, omit, or flat-out copy the wrong year’s data. This is a genuine Komatsu publication printed in 1992 – revision marks are stamped right on the page corners. The serial ranges are clear: PC100-5 from 28001 up, PC120-5 from 30001 up, and PC120-5 MIGHTY from 36601 up. If you need to verify a solenoid valve resistance or the correct hydraulic hose routing, you go to the original. Anything else is a gamble. Manual Transmission”>Manual Transmission diagnostics are a different field; for excavator hydraulics there’s only one source that counts.

FAQ

Does the manual include wiring diagrams for the electrical system?

Yes. Section 10 has separate chapters for Electrical Wiring Diagram and Electrical Circuit Diagram, plus connector tables and troubleshooting charts in Section 20.

What is the page count for the hydraulic section alone?

Hydraulic piping, circuits, and component descriptions span over 200 pages. Exact count not given here, but the Structure and Function section alone is roughly 100 pages.

Can I use this manual on a PC200-5?

No. This manual covers only the PC100-5, PC120-5, and PC120-5 MIGHTY models. Different engine and hydraulic system.

Are the torque specs given in foot-pounds or Newton-meters?

Both. The OEM manual lists imperial units (ft-lb) as primary with metric equivalents in parentheses. Valve clearance is given in inches and mm.

I’ve been turning wrenches for 28 years, and I don’t trust aftermarket data for critical engine and hydraulic work. This Komatsu Workshop Manual from 1992 gives you everything you need to rebuild, adjust, and diagnose the PC100-5, PC120-5, and PC120-5 MIGHTY – without the guesswork. Stop chasing bad info. Access the Factory Manual and keep it on your tablet or print the pages you need. It’ll pay for itself the first time you avoid a torn-down machine waiting on parts that weren’t the problem.