Description

Komatsu PC100-2, PC100L-2, PC120-2 1985 Workshop Manual

If you’re wrenching on a Komatsu PC100-2, PC100L-2, or PC120-2 from the mid-80s, you already know the cost of guessing wrong. A mis-torqued head bolt on the 6D95 engine means a blown gasket and a week of downtime. I’ve seen it happen. That’s why I keep the factory Komatsu PC100-2, PC100L-2, PC120-2 1985 Workshop Manual on the bench. Not a third-party reprint, not a scan of a scan — this is the actual OEM document Komatsu issued to its dealers. 304 pages, original 1985 publication, and every torque value came straight from the engineers in Osaka. You don’t fix these machines with guesswork; you fix them with page 12-1 in your hand.

Engine Section: Structure, Function, and Assembly (11-13)

The manual breaks the engine into three chunks. Section 11 covers structure: cylinder head, piston rings, timing gear train. Section 12 is where you’ll live — testing and adjusting. Compression test specs, injector pop pressures, valve clearance settings. Section 13 gets into disassembly and assembly. That’s where the torque sequences matter most. The manual shows you the order and the angle-tighten steps for the 6D95 main bearing caps. Miss one step and the crank walks. I’ve had to redo that job — not fun. Get the factory page open before you pull the oil pan.

Hydraulic System: Section 62 Testing and Adjusting

Hydraulic drift on a PC120-2 will eat your day. Section 62 gives you the pump flow test procedure, relief valve settings, and pilot pressure checks. Page 62-5 lists the exact PSI for the main relief — not a range, an exact number. You can dial it in with a gauge and a feeler. The manual also tells you which ports to tee into and what adapters fit. If you’ve ever fought a Komatsu hydraulic system that won’t lift, this section is your first stop.

For the DIY owner who runs a backhoe attachment, understand that Section 63 (disassembly and assembly) includes seal replacement steps for the control valve spools. You’ll need a soft-jawed vise and the special puller tool Komatsu calls out. Ignore that and you’ll score the bore. I’ve got a set of those pullers — worth every penny.

Undercarriage Maintenance Standards (Section 34)

Track sag, sprocket wear limits, roller flange thickness — Section 34 lays it out in numbers. Page 34-8 shows the wear limit for track link pitch. If you’re rebuilding undercarriage on a PC100L-2 long-track model, that table keeps you from replacing good parts. The manual also includes the tensioning procedure with the grease gun and the pressure relief valve. Don’t skip the warning about never cracking the fitting while under pressure — that’s how you break a jaw.

Power Train: 7 Systems Covered

Transmission, torque converter, final drives — the power train runs from Section 21 (structure and function) through Section 24 (maintenance standards). Section 23 is disassembly of the manual transmission. If you need a refresher on how a Manual Transmission works, the Wikipedia article is decent, but this manual gives you the actual end-play shim specs for the PC120-2 output shaft. You won’t find that in a generic write-up.

The manual lists all bearing numbers and seal sizes — you can order parts without disassembling first. That’s time saved on the job. Use the OEM numbers from page 23-1, not aftermarket cross-references that may be wrong.

Electrical System: Section 88-1 Coverage

Section 88 is short — 10 pages — but it covers the charging circuit, starter motor, and the key switch wiring. The schematic is hand-drawn in Komatsu’s style with wire colors and connector pinouts. If you’ve got a no-crank condition on a PC100-2, start with page 88-2. That gives you the starter relay test.

Don’t try to trace wires without the factory diagram. Aftermarket diagrams often swap colors and leave out the diode in the alternator circuit. I’ve seen guys fry a brand-new alternator because they assumed it was a standard 3-wire hookup. The manual tells you it’s a 4-wire with an excitation resistor. Saved me once.

Who Needs This Manual?

If you own a PC100-2, PC100L-2, or PC120-2, you need this. The home-garage enthusiast who does oil changes will learn to check the hydraulic pilot filter — most owners don’t even know it exists. The shop foreman with six mechanics needs it to keep builds consistent. Beginners: don’t touch the final drive gear backlash without reading Section 24 first. The manual uses standard imperial tools: 1/2-inch drive torque wrench up to 300 ft-lbs, plus crowfoot adapters for the hydraulic fittings. You don’t need special Japanese tools — just a clean workbench and this manual.

Compare this to a third-party mechanic’s tip sheet. That aftermarket guide might say “tighten to spec” without giving the value. This manual gives you foot-pounds, inch-pounds, and angle degrees where required. There’s no guesswork. If you’ve been burned by aftermarket junk before, you’ll appreciate that every page has a revision mark — you can see what changed in the field. That’s traceability you won’t get from a pirated PDF.

Safety? The manual has warnings for high-pressure oil burns, track tension hazards, and electrical shock from the glow plug system. Don’t skip the note on page 61-1 about bleeding the accumulator before removing the hydraulic pump. I know a guy who ignored it and got a face full of ATF.

Related manuals you might need: Komatsu WA65-5 WA70-5 WA80-5 2005 Workshop Manual for wheel loaders, Komatsu WH609-1E0 WH613-1E0 WH713-1E0 WH714H-1E0 WH716-1E0 Workshop Manual for excavator wheeled variants, and Komatsu PW95R-2 Workshop Manual – 520 Pages of Factory Specs for larger machines. All direct OEM, same factory source.

For more background on transmission fundamentals, the Manual Transmission article from Wikipedia gives a good overview, but this manual is what you need when the PC120-2 won’t move in gear.

FAQ

Does this manual cover the engine overhaul completely?

Yes. Sections 11-13 take you through structure, testing, and full disassembly/assembly of the 6D95 engine. Page 13-15 shows the cylinder head bolt torque sequence with five stages. You get piston ring end gap specs, main bearing clearances, and injector timing data. If you are rebuilding the engine, this is the only document you need.

Can I use this manual for a PC120-2 with a different serial number range?

It covers all PC100-2, PC100L-2, and PC120-2 models built up to 1985. After that, Komatsu issued revisions which are marked in the manual — you’ll see the revision numbers on each page. Check your serial number against the introduction.

Access the Factory Manual now and get the original Komatsu repair data on your screen before you pull a single bolt. No reprints, no aftermarket speculation — just 304 pages of what the factory sent to its own technicians. You’ll save yourself at least one trip to the parts counter with the right numbers.