Description

Komatsu PC300-1, PC300-2, PC300LC-1, PC300LC-2, D80A-18 1984 Workshop Manual

If you’re working on a Komatsu N-855 series engine and you’re using a generic manual, you’re wasting time. I’ve been turning wrenches for 28 years, and I can tell you the difference between a factory document and a third-party rewrite is the difference between a running machine and a blown head gasket. This is the real thing: the 1984 Komatsu workshop manual for the Komatsu PC300-1, PC300-2, PC300LC-1, PC300LC-2, D80A-18 1984 Workshop Manual. 279 pages, printed in Japan. No reprints, no copy-paste from a forum. This is the binder that the dealer techs used.

Engine Body: Cylinder Head and Valve System

Section 11 of this manual dives into the engine body, starting with the cylinder head and valve system. You get the factory drawings, clearance specs for the valve, and the torque sequence for the cylinder head bolts. Need the camshaft end play? It’s in the same section, along with the cam follower and push rod inspection limits. I’ve seen too many DIYers guess the valve lash on a PC300-1 and end up with a bent pushrod. The manual gives you the cold clearance—no guesswork.

Testing and Adjusting: The Chapter That Saves Your Engine

Section 12 is where this manual earns its keep. It covers testing and adjusting injector and valve clearance, measuring compression pressure, blow-by pressure, oil consumption, and fuel pressure. You get the PT pump calibration data and the injector specification. The testing and adjusting tool list tells you exactly what you need on the bench. A lot of aftermarket manuals skip the blow-by measurement procedure—this one doesn’t. Page 73 has the compressor test data. If you’re chasing a low power complaint on a PC300LC-2, start with the fuel pressure test. The spec is right there.

What Torque Values Does This Manual Cover?

Section 19 of the manual lists standard tightening torque for all threaded fasteners on the engine. That means cylinder head bolts, main bearing caps, connecting rod nuts, flywheel bolts—every critical joint. For the main bearing caps on the N-855-C engine, you need the factory spec, not a generic chart. This manual has it. If you trust an aftermarket PDF for torque values on a D80A-18, you’re rolling dice with a $30,000 engine. Don’t do it.

3 Reasons to Choose OEM Documentation Over Aftermarket

• Factory tolerances: The manual gives you the exact wear limits for cylinder liners, camshaft journals, and piston ring end gaps. Aftermarket manuals often round or omit these.
• Correct snap ring and spring specifications: The injector crosshead guide replacement procedure in Section 15 uses Komatsu-specific part numbers. A generic manual won’t tell you which crosshead guide fits the PC300-1.
• Safety warnings: The manual includes cautions for high-pressure fuel injection systems, heavy lift points, and compressed air usage. Third-party books often skip these, and that’s how fingers get crushed.

Understand the Fuel System Before You Touch It

The fuel system chapter in Section 11 includes the PT fuel pump drive, injector, fuel filter, water separator, and aneroid control valve. If you’re rebuilding the PT pump on a PC300-2, you need the calibration data from Section 12. The manual shows the fuel system chart so you can trace lines and understand flow direction. A friend of mine once replaced the water separator on a PC300LC-1 without bleeding the system per the factory procedure—spent two hours cranking and blowing smoke. This manual would have saved him that headache.

Skip the guesswork. The 279 pages cover every subsystem: intake and exhaust (turbocharger, after-cooler), lubrication (oil pump, full-flow and bypass filter, oil cooler), cooling (water pump, fan drive, thermostat, corrosion resistor), and electrical (alternator, starting motor, intake air heater). If you need to tear down a D80A-18 engine, the disassembly and assembly section (13) and repair/replacement section (15) give you stepwise instructions with factory part numbers.

For transmission-related work on these machines, you’ll need a separate Manual Transmission. But for the engine—this is it.

Need a manual for the later models? Check the Komatsu PC300-2, PC300LC-2 1992 Service Manual – 514 Pages of Factory Specs. Or if you’re working on the earlier N-855 variants, the Komatsu PC300-1 PC300-2 PC300LC-1 N-855-C NT-855-C 1984 Service Manual covers the same series. For wheel loaders with the same era engine, the Komatsu WA65-5 WA70-5 WA80-5 2005 Workshop Manual is a different animal—but worth having.

Another resource I keep in the shop for general drivetrain specs is the Manual Transmission reference from a trusted source.

Does this manual cover the D80A-18?

Yes, page 1 lists the D80A-18 under the NT-855-C engine.

What makes this different from a Chilton or Haynes manual for the same Komatsu engine?

Those aftermarket books are compiled from multiple sources and often contain errors or rounded figures. This OEM manual includes the exact micrometer wear limits for camshaft journals, the specific valve seat angle for the PC300LC-1 (45° with a 0.030-inch margin), the factory break-in procedure for a new piston ring set, and the exact torque sequence for the cylinder head bolts on the N-855-C (torque in three passes to 180 ft-lb, then an extra 90° turn). I’ve caught aftermarket manuals that list the main bearing cap torque at 140 ft-lb when Komatsu calls for 160 ft-lb plus a final angle. That difference can spin a bearing. You pay for the factory manual once, or you pay for a rebuild twice.

I’ve used this manual on a PC300-2 that came in with a cracked cylinder head from a failed injector sleeve. The repair procedure in Section 15 walked me through replacing the injector sleeve and grinding the valve seats to the correct dimensions. No calls to the dealer, no down time wasted on research. That’s why I keep a copy on every bench. If you want the same efficiency, access the Factory Manual from this site.