Description

Komatsu D51EX-22, D51PX-22 Workshop Manual – Factory Specs, Full Disassembly

Never trust a torque spec from an aftermarket manual. I’ve seen more stripped bolt holes and blown seals from someone grabbing a random number off the internet than I can count. This Komatsu D51EX-22, D51PX-22 Workshop Manual is the real thing — 1230 pages of factory data direct from Komatsu. No guessing, no aftermarket guesswork. If you’re tearing down a D51EX-22 or D51PX-22, this is the only paper you need on the bench.

Komatsu D51EX-22, D51PX-22 Workshop Manual: 1230 Pages of Factory Data

The manual is split into major sections: Index and Foreword (00), General specs (01), Structure, Function and Maintenance Standard (10), Standard Value Tables (20), Testing and Adjusting (30), Troubleshooting (40), and Disassembly and Assembly (50). Plus a 90-series section for other content. You get the full revision tracking — page marks like “G” for replace, “H” for add — so you know exactly which pages are current. That matters when you’re ordering parts.

Page 30-1 kicks off the testing and adjusting procedures. Need to verify charge pressure on the HST pump? That’s where you go. Page 50-1 starts disassembly and assembly — every fastener sequence, every seal orientation. If you skip the order on a final drive rebuild, you’re buying new bearings. I’ve seen it.

Standard Tightening Torque Tables: Why OEM Specs Matter

The manual includes dedicated tables for bolts and nuts, hose nuts, split flange bolts, flared nuts, O-ring boss joints, O-ring boss plugs, and two types of hose fittings (taper seal and face seal). Each table gives torque values in foot-pounds and Newton-meters. Aftermarket manuals often round these off or use generic numbers. Komatsu doesn’t. If the chart says 74 ft-lb for a split flange bolt, you torque it to 74 ft-lb — not 70, not 80.

3 Hydraulic Systems Covered: HST, Work Equipment, and Fan Pump

Section 10 breaks down the HST hydraulic equipment arrangement: charge pump, towing valve, safety-suction valve, and motor control valve with solenoid and EPC valve details. The CLSS (Closed Center Load Sensing) system for work equipment gets its own subsection — unload valve, pressure compensation valve, LS bypass valve. Fan pump is covered under work equipment hydraulic system 2. If you’ve ever chased a drifting blade or a weak steering response, these pages tell you exactly which valve to test and at what pressure.

Get the Right Torque Data for Bolts, Nuts, and Hose Fittings

Stop using a generic torque chart from a Snap-on poster. This manual gives you O-ring boss plug torques, split flange bolt torques, flared nut torques — all specific to the D51EX-22 and D51PX-22. The hose torque table includes both taper seal and face seal types. If you over-torque a face seal hose, you’ll deform the sealing surface. Under-torque it and you get a leak at the worst possible moment. The table tells you exactly what it needs.

Why a Factory OEM Manual Beats Aftermarket Copies

Aftermarket documentation frequently omits the revision history, the wire code classification (thickness, color, and reading method), and the hoisting instructions with wire rope specs. This manual includes a full push-pull coupler section with disconnection and connection procedures for three different coupler types. Try finding that in a third-party reprint. You won’t. The conversion tables alone — method of using, coating materials list — save you from hunting down SAE-to-metric equivalents when you’re elbow-deep in a hydraulic line.

Electrical System Diagnostics: Sensors and Controllers

The electrical system section covers the monitor panel, engine controller, HST controller, electric lever for travel, KOMTRAX terminal, and a long list of sensors: brake oil pressure, hydraulic oil temperature, HST circuit oil pressure, air cleaner clogging, decelerator pedal potentiometer, brake pedal potentiometer, fuel control dial, fuel level, charge filter clogging, coolant temperature, engine oil pressure switch, engine rotation, boost pressure and temperature. If your D51EX-22 won’t shift into travel speed 2, or the parking brake won’t release, the troubleshooting section on page 40-1 walks you through the logic. Don’t throw parts at it.

Related manuals you might need: Komatsu D51EX-22 D51PX-22 2007 Operators Manual – Factory OEM for daily operation, Komatsu WA65-5 WA70-5 WA80-5 2005 Workshop Manual if you’re running a mixed fleet, and Komatsu WH609-1E0 WH613-1E0 WH713-1E0 WH714H-1E0 WH716-1E0 Workshop Manual for wheel loader work.

For background on driveline principles, check Manual Transmission basics. And if you need to understand how the HST control system differs from a Manual Transmission, the manual explains the straight travel correction control and gear shift control system in detail.

Does this manual cover the ripper cylinder?

Yes, section 10 under Work Equipment Cylinder includes lift, tilt, angle, and ripper cylinder procedures plus the piston valve for the angle cylinder.

I’m rebuilding the track frame – what torque specs are given for the recoil spring?

The manual does not list a specific recoil spring torque in the tables I see, but the Under Carriage and Frame section (10) covers main frame, track frame and recoil spring, suspension, idler, track roller, carrier roller, and track shoe. Recoil spring adjustment is described in the function and maintenance standard text. You’ll need to use the standard tightening torque tables for the retaining bolts, which are provided in the foreword section. If you need the exact preload procedure, page 10-28 (track frame subsection) outlines the measurement method. Always refer to the OEM manual before applying any load to a compressed spring – safety first.

If you’re tired of chasing bad data and want a manual that matches every bolt, sensor, and hydraulic line on your Komatsu, this is it. Access the Factory Manual now and keep it on the toolbox rather than relying on a forum post from 2014.