Description

Komatsu PC20R-8, PC27R-8 Workshop Manual – Factory OEM Specs for Hydraulic Excavator Repair

You get a machine in the bay with a hydraulic leak, or a control valve that won’t stroke right, and the first thing you need is the real OEM data. Not some third-party reprint that fudged the torque table. The Komatsu PC20R-8, PC27R-8 Workshop Manual on this page is the exact document Komatsu issued for their shop techs. 298 pages of verified factory information. I’ve torqued head bolts on half a dozen excavators, and I can tell you: if you use the wrong LS differential pressure spec, you’ll be chasing drift all afternoon. This manual ends that guesswork.

Standard Tightening Torque: Why the Factory Values Matter

Look at the table of contents—right after the safety section and hoisting instructions, there’s a full page on standard tightening torque. That’s the baseline for every bolt on the machine. I’ve seen guys use a generic inch-pound chart and snap a swing motor mount bolt because they didn’t account for Komatsu’s specific thread grade. This manual lists the torque values for each bolt diameter and grade. You need that table on page [DATA NEEDED] if you want to avoid comebacks. I keep a copy of this torque chart laminated next to my box.

298 Pages of OEM Data

This isn’t a condensed guide. 298 pages covers every major system: power train, swing circle, final drive, track frame, recoil spring, carrier rollers, track rollers, steel shoe. The hydraulic section alone splits into PC20R-8 and PC27R-8 circuits, with separate diagrams for each. You get the CLSS (Closed Center Load Sensing), the TCC valve, LS valve, servo piston, control valve, swivel joint, swing motor, travel motor, cylinders, accumulator, PPC valves, solenoid valves, and full electrical diagrams in three parts. Then the testing and adjustment section has procedures for engine speed, valve clearance, compression pressure, fan belt tension, injection timing, accelerator stroke—all with the factory tolerances. The removal and installation section breaks down every component from starter motor to blade cylinder, with torque specs and sealant requirements. And the standard maintenance section gives you rebuild specs for swing machinery, final drive, sprocket, rollers, and work equipment. That’s depth you won’t find in a Chilton or Haynes.

Does This Manual Cover the Hydraulic System?

Yes, and it does it properly. The hydraulic system section is split by model: PC20R-8 and PC27R-8 each get their own circuit diagram and pump description. You get the flow path for the CLSS, the LS valve adjustment procedure, and the PC valve regulation steps. For both models, there’s a dedicated subsection on “Control and regulation of the LS differential pressure and adjustment of the LS valve” and “Regulation of the PC valve.” That means you can set the pump compensator correctly without guessing. The manual also covers elimination of residual pressures, bleeding air from the circuits, and checking for internal leakages in cylinders, swing motor, and swivel joint. If you’re chasing a drift, the section on “Control of hydraulic drifts – analysis of the causes of a drift” gives you a systematic method rather than swapping parts.

Adjustment of Valve Clearance and Engine Specs

Under testing and adjustment, you’ll find a procedure for adjustment of valve clearance, measurement of compression pressure, and control of injection timing. These are the kind of specs that change with serial number breaks—this manual covers PC20R-8 F30791 and up, PC27R-8 F31103 and up. Aftermarket manuals often have generic values that don’t match the actual engine. I’ve seen a guy set valve lash too tight because a cheap manual said .008 inch when Komatsu calls for a different clearance. The manual also lists special tools needed for each job. Don’t skip the “Special tools” subsection—Komatsu has specific tools for a reason.

Get the Right Torque Data

Torque is the single most common place I see mistakes. The manual includes the standard tightening torque chart, but also lists specific torques throughout the removal and installation sections. For example, when you install the cylinder head, the torque sequence and final angle are given. When you reassemble the swivel joint, the bolt torque for the flange is specified. That’s the kind of detail that keeps an excavator running 5000 hours without a leak. Compare that to a generic reprint that might say “tighten securely.” This manual gives you the number, the unit in ft-lb or in-lb, and the order. That’s what separates a repair from a hack job.

Now, about aftermarket documentation: I don’t trust them. I’ve opened third-party manuals that claimed to be “OEM equivalent” and found missing pages and wrong part numbers. This one is a direct scan of the Komatsu shop manual. The table of contents lists every section, the page numbers are original, and the schematics are crisp. If you want to work on these machines and not waste time chasing down leaks or stripped threads, get the factory document. It’s the same one I use in my shop.

Related manuals you might need: Komatsu PC20R-8, PC27R-8 Service Manual – 196 Pages of Factory Specs is a lighter version if you only need service intervals, but for a full rebuild you want this 298-page manual. The Komatsu PC20R-8, PC27R-8, PC25R-8 Service Manual | Shop Manual 239 Pages includes the PC25R-8 if you have that model. And if you’re working on a wheel loader, check the Komatsu WA65-5 WA70-5 WA80-5 2005 Workshop Manual.

For general background on how a Manual Transmission works, you can read up, but remember an excavator uses hydrostatic drive—different beast entirely. Still, understanding gear reduction helps when you’re rebuilding the final drive. Another reference on Manual Transmission design can give context for the sprocket and idler adjustments in this manual.

Frequently Asked Questions

Is this manual the same as the one Komatsu dealers use?

Yes. This is the official Komatsu shop manual for the PC20R-8 and PC27R-8. The part number and serial number range match the dealer-issued document.

Does it include wiring diagrams?

Yes. Three full pages of electrical diagrams covering the entire machine.

Can I use this for both PC20R-8 and PC27R-8?

Yes. The manual covers both models separately, with dedicated sections for hydraulic systems, LS valve adjustments, and work equipment. The table of contents clearly splits PC20R-8 and PC27R-8 procedures where they differ.

What about track tension?

There is a dedicated procedure under Testing and Adjustment for “Control and adjustment of the track-shoe tension.” The manual gives the correct sag measurement and the method using the recoil spring. That section alone saves you from over-tightening and ruining the sprocket bearings.

Stop relying on internet forum guesses. Access the Factory Manual from AutoRepairManuals and get the actual torque values, hydraulic pressures, and assembly drawings Komatsu engineers specified. Your machine will run longer, and you’ll waste less time on re-dos.