Description

Komatsu PC40-6, PC20-6, PC30-6 Workshop Manual

If you’ve ever cracked open an aftermarket manual and found a torque value that didn’t match the bolt on your bench, you know the frustration. I lost a head gasket that way once. This Komatsu PC40-6, PC20-6, PC30-6 Workshop Manual is the factory book — 345 pages of the exact data Komatsu intended for their PC20-6 (serial 24001 and up), PC30-6 (10001 and up), and PC40-6 (10001 and up) excavators. No third-party rewrites, no blurred reprints. This is the original SHOP MANUAL used by Komatsu dealers.

I spent years turning wrenches on these machines at a San Antonio shop. The difference between a factory manual and a reprint shows up when you’re bleeding the hydraulic cylinders or setting the valve clearance. Reprints skip the revision pages — this one includes the full list of revised sheets and the TABLE OF JUDGEMENT STANDARD VALVE. That table alone saves you from guessing whether a valve spool is within spec.

Valve Clearance Adjustment: PC20,30-6 vs PC40-6

Valve clearance specs differ between the PC20,30-6 and the PC40-6. Section 20 of this workshop manual gives separate procedures for each. The adjustment for the PC20,30-6 starts on page 20-3, and the PC40-6 procedure follows right after. You get the factory feeler gauge sizes and the order to tighten the locknuts. I have seen techs use a generic spec and burn an exhaust valve. Don’t be that guy. Use the Komatsu data.

Electrical Circuit Diagnostics

Electrical problems on these excavators usually trace back to a bad ground or a corroded connector in the harness. The ELECTRICAL CIRCUIT DIAGRAM in section 10 shows every wire, connector, and component. Page 10-30 has the full schematic for the PC20-6 through PC40-6. You can trace the starter motor circuit, the alternator charge wire, and the safety relay logic. No aftermarket wiring diagram I have seen matches the clarity of this original Komatsu print. The manual also covers resistance checks for the sensors — critical when you’re diagnosing a no-crank condition.

3 Testing Sections That Prevent Guesswork

Section 20 has a dedicated TESTING AND ADJUSTING TOOL LIST. You need to know which pressure gauge and adapter to use before you connect anything to the hydraulic test ports. The manual walks you through measuring compression pressure, adjusting fuel injection timing for both engine variants, and bleeding air from hydraulic cylinders. The HYDRAULIC CIRCUIT SCHEMATICS show the flow paths for the 6-spool, 3-spool, and 2-spool control valves. If the arm lacks power, the troubleshooting table (item 2 in the TOC) tells you which pressure to check first.

Disassembly and Assembly: Factory Sequence

Section 30 covers removal and installation for every major component — cylinder head, fuel injection pump, swing motor, travel motor with reduction gear, and the center swivel joint. The manual separates the procedures for PC20,30-6 and PC40-6 where they differ. For example, the cylinder head removal steps are not the same between the 20/30 and the 40. Torque sequences are listed in ft-lbs, not N-m — important for those of us who still use beam-style torque wrenches. The table of special tools tells you exactly which puller or installer Komatsu expects you to use.

OEM Origin: Why This Manual Wins

This workshop manual came from Komatsu’s own printing press. The original file name — KOMATSU_PC20-6-PC30-6-PC40-6_Workshop_Manual_en-35328018146.pdf — confirms it is a direct scan of the factory document. Aftermarket manuals often renumber pages, skip the revision log, or compress the diagrams until they are unreadable. This one preserves the original page numbers, the blueprints, and the judgment standards you need to pass a leak-down test. For background on manual transmission principles that apply to the travel motor reduction gear, see Manual Transmission on Wikipedia. Another reference for transmission basics is Manual Transmission.

If you are working on a Komatsu PC20-6, PC30-6, or PC40-6, you need the official data — not a reprint, not a rewritten summary. This manual gives you the exact specs for the valve clearance, hydraulic pressures, and electrical testing. I have used it to overhaul three PC40-6 swing motors, and every bolt torque matched what Komatsu intended. Access the Factory Manual from AutoRepairManuals and keep a copy on your shop tablet or print it for the bench.

Related manuals: KOMATSU PC40-6 Hydraulic Excavator Operation Manual, Komatsu WA65-5 WA70-5 WA80-5 2005 Workshop Manual, Komatsu WH609-1E0 WH613-1E0 WH713-1E0 WH714H-1E0 WH716-1E0 Workshop Manual.

Frequently Asked Questions

Does this manual cover the engine overhaul?

Yes, section 30 covers disassembly and assembly of the engine, cylinder head, fuel injection pump, and related components.

What is the difference between this factory manual and a reprint?

Reprints often miss revision updates, have blurred diagrams, and lack the official Komatsu judgment standard table. This manual is a direct scan of the original, with clear schematics and all pages intact. It includes the TABLE OF JUDGEMENT STANDARD VALVE, which is critical for hydraulic testing. The electrical circuit diagram is legible, not a photocopy of a photocopy. If you are paying for a manual, you want the one that Komatsu engineers used — this is that manual.