Description

Komatsu D31EX, D31PX, D37EX, D37PX 2004 Workshop Manual

If you have ever pulled a head bolt on a Komatsu D31EX or D37PX and wondered whether the torque value in your hand-me-down PDF matched the factory print, you already know why this manual matters. I have seen too many guys skip the step where they check the actual OEM spec, then wonder why the HST charge pressure bleeds off or why the engine stop solenoid linkage binds. This 2004 Komatsu workshop manual—407 pages, factory-issued, not a reprint—gives you the numbers Komatsu stamped at the factory. No chasing after aftermarket summaries that misquote the fuel injection timing or leave out the brake pedal linkage adjustment procedure.

What the 407 Pages Cover

Start with section 01 GENERAL: the weight table, fuel/coolant/lubricant specs, and the specification drawing that tells you exactly which engine mounts to which chassis. Then section 10 STRUCTURE AND FUNCTION, MAINTENANCE STANDARD goes deep into every system on the machine. You get cooling system flow diagrams, HST pump arrangement, steering and brake control valve IDs, the whole power train system breakdown. The solenoid valve section alone saves you hours when you are diagnosing a charge safety valve that sticks. And if you have ever had to trace a parking brake quick return circuit without a schematic, you will appreciate the HST brake quick return circuit explanation on those pages.

Fuel, Cooling, and Brake: Three Systems You Cannot Ignore

The table of fuel, coolant and lubricants is right there in section 01. But the real work happens in section 20 TESTING AND ADJUSTING. You get the standard value table for the engine, chassis, and electrical system. That means you can measure compression pressure, check blow-by, and adjust valve clearance against factory numbers—not some forum guess. Fuel injection timing adjustment? The procedure is spelled out with the tools list. Bleeding air from fuel circuit? Step by step. Brake pedal linkage adjustment? Specified. The manual treats every system as something that can kill you if you skip the order of events—and it gives you that order.

Valve Clearance and Injection Timing

Look at the testing section: “ADJUSTING VALVE CLEARANCE” and “TESTING ADJUSTING FUEL INJECTION TIMING.” These are not vague descriptions. You get the exact feeler gauge sizes, the rotation positions for the engine, and the sequence that does not leave exhaust valves tight. I have used manuals that say “adjust as necessary.” That is not a manual. Here, the procedure ends with the clearance spec in thousandths of an inch—or millimeters, because Komatsu works metric. Either way, it is the OEM number. The same discipline applies to the fuel control linkage and the decelerator pedal linkage. If you are a tech who has to fight an engine that surges at idle, start with those adjustments.

Who Needs This Workshop Manual?

Home garage guys who bought a used D31PX from a auction site and want to do their own undercarriage work. Small fleet owners who need to keep a D37EX running without dealer labor rates. Even experienced mechanics who have worked on other yellow iron—the HST system here uses a specific charge pump cut-off valve that is not in the generic service data. If you are planning to tear into the final drive, the idler adjustment, or the track shoe tension, this manual has the torque sequence and the alignment specs. And if you are chasing electrical gremlins, the troubleshooting section E-1 through E-11 covers the starting motor, headlamp, wiper, air conditioner, and the parking brake solenoid release. You get connector pin numbers and circuit diagrams. No guessing.

Source Validity: Why OEM Matters

This is Komatsu’s own publication, printed in Japan in 2004. The part number SEBM025607 is stamped on every page. The aftermarket PDFs that float around often omit the “LIST OF REVISED PAGES” at the front—those are critical because Komatsu issued revisions for pages 10-9-1, 10-51-3, and others. Without those revisions, you might be using an obsolete spec for the charge safety valve. This copy includes all revisions up to revision (7). That is the difference between a repair that holds and one that comes back on a hook. Manual Transmission systems have their own set of tolerances, but this manual covers the hydrostatic and power shift setups used on these Komatsu models.

Does this manual cover the D39EX or D39PX?

No. This manual specifically covers D31EX, D31PX, D37EX, and D37PX with serial numbers starting at 50001 and 5001 respectively. The D39 is a different machine. Use Komatsu D31EX D31PX D37EX D37PX D39EX 2007 Workshop Manual for later models.

What torque specs are included?

You get torque values for the engine cylinder head, connecting rod bolts, flywheel, final drive components, track frame bolts, and more. They are listed in the standard value tables and in the disassembly/assembly section 30. For example, the valve clearance adjustment procedure gives you the intake and exhaust clearance for a cold engine. The fuel injection line torque is specified in the testing section. Every torque number is Komatsu’s own, not an aftermarket approximation. If you need the exact value for the charge pump mounting bolts, it is in section 10. The manual also includes tightening sequences for multi-bolt joints like the cylinder head and the HST motor flange. Do not trust a generic chart for these bolts—the material grade and thread pitch are specific to the SAA4D102E-2 engine.

If you work on any of these four machines, you need the actual factory print on your bench—not a third-party translation, not a scanned copy of a copy. One hundred and seven pages of disassembly and assembly procedures alone, plus the troubleshooting charts that walk through E-mode electrical faults and H-mode hydraulic/mechanical faults. The manual also includes a towing valve adjustment procedure and the inching valve calibration. Grab the 2004 edition while it is still available in original PDF. No reprints, no vendor summaries. Manual Transmission references aside, this is the binder you want when the machine drops its charge pressure at 6:00 PM on a Friday. Access the Factory Manual from AutoRepairManuals and get back to turning wrenches with the right numbers in your hand.

Related manuals you may need:

• Komatsu D31EX, D31PX, D37EX, D37PX, D39EX Operators Manual – OEM
• Komatsu D31EX, D37EX, D39EX, PX-21 Service Manual – OEM Factory Specs