Komatsu 125-2 Series Diesel Engine Shop Manual SEBM006410 – 6D125-2 S6D125-2 SA6D125-2 SAA6D125-2

Description

Komatsu 125-2 Series Diesel Engine Shop Manual — 6D125-2, S6D125-2, SA6D125-2, SAA6D125-2

This Komatsu 125-2 Series Diesel Engine Shop Manual (document number SEBM006410) is the complete service, repair, testing, and maintenance reference for the 6D125-2, S6D125-2, SA6D125-2, and SAA6D125-2 diesel engines. Prepared for operations performed in a service workshop, it gives the technician accurate technical information for every major engine system — from structure and function through disassembly, assembly, and component repair. With 366 pages of procedures, specifications, torque values, and diagnostic charts, this manual covers the full scope of work on these Komatsu engines.

File Details

• Manual Type: Engine Shop Manual
• Brand: Komatsu
• Engine Models: 6D125-2, S6D125-2, SA6D125-2, SAA6D125-2
• Language: English
• Page Count: 366 pages
• File Format: PDF
• Document Number: SEBM006410
• Date: 2023-2024

Chapters Covered

• 01 GENERAL
• 11 STRUCTURE AND FUNCTION
• 12 TESTING AND ADJUSTING
• 13 DISASSEMBLY AND ASSEMBLY
• 14 MAINTENANCE STANDARD
• 15 REPAIR AND REPLACEMENT OF PARTS

01 GENERAL — Specifications and Performance Data

The GENERAL chapter opens with applicable machine listings and full engine specifications for each 125-2 series variant. You will find the 6-cylinder, 125 × 150 mm bore and stroke configuration, 11.04 L (11,040 cc) total piston displacement, and 1-5-3-6-2-4 firing order. The chapter provides dimensions (overall length, width, height), performance figures (flywheel horsepower, maximum torque, high and low idling speeds, minimum fuel consumption ratio), dry weights, fuel injection pump types, governor types, lubricating oil and coolant capacities, alternator and starting motor ratings, battery requirements, turbocharger information, and air compressor data. General assembly drawings show the engine from multiple views with crankshaft center and flywheel housing reference points. Engine performance curves plot torque and flywheel horsepower across the operating speed range for the various applications.

11 STRUCTURE AND FUNCTION — How Every System Works

This chapter breaks down the engine into its major systems and explains the structure and function of each component. It serves both as a guide to understanding the engine and as reference material for troubleshooting.

Intake and Exhaust System — Covers the air cleaner (current FHG type with guide vane, primary element, safety element, vacuator, and dust pan), the turbocharger (Schwitzer S3A and Garrett TO4E types with full component breakdowns and specifications), and the aftercooler (core, cover, intake manifold, water inlet and outlet ports).

Engine Body — Details the cylinder head (direct fuel injection, 4-valve, divided type with one head per cylinder, press-fitted valve seat inserts, floating type cylinder head cover seal), cylinder block (crankshaft with 7 bearings, camshaft with 7 bearings, front seal, piston cooling nozzle, wet type cylinder liner with plateau honing finish and gas soft nitriding treatment), main circulation part, timing gear (with tooth counts for water pump drive gear, main idler gears, oil pump drive gear, idler gear, injection pump drive gear, camshaft gear, and crankshaft gear), valve system (rocker arm shaft, cam roller, crosshead, valve springs, intake and exhaust valves, valve timing diagram), and flywheel and flywheel housing (ring gear tooth counts for various machine models).

Lubrication System — Includes the lubrication system chart, oil pump (gear type with pump speed ratio of 1.571 times engine speed and main relief valve set pressure), regulator valve (set pressure 0.36 ± 0.15 MPa), oil filter (filtration area 0.84 m² or 1.3 m²), bypass filter, oil cooler (effective area varies by engine model), and safety valve (set pressure 0.2 ± 0.02 MPa).

Fuel System — Covers the fuel system chart, fuel injection pump (DENSO NB (EP9), BOSCH PE-P (PS3S), and ZEXEL types), governor (RSV centrifugal all-speed type), fuel 2-stage set control motor mount, engine stop motor, 2-stage set control motor, magnetic switch (fuel cut solenoid), boost compensator (with full component diagram and function explanation), fuel injection nozzle (multi-hole type with injection pressure adjustment data), and fuel filter (filtration area 0.3 m²).

Cooling System — Includes the cooling system chart, water pump (centrifugal gear drive with pump speed 1.5 times engine speed), thermostat (valve cracking temperature, full opening temperature, full opening lift), corrosion resistor, and fan drive (belt configurations, pulley diameters for various machine applications).

Electrical System — Covers the alternator (Nikko Denki and Sawafuji Denki open types with built-in regulator), starting motor (Nikko Denki sealed type, 24 V, 7.5 kW or 11 kW with pinion tooth counts and connector specifications), and electrical intake air heater (rated voltage DC22 V, rated current 111 A or 27.3 A).

Accessory — Details the air compressor (ZEXEL single cylinder double acting, discharge volume 340 cc/rev, air pressure 0.83 MPa, unloader valve opening and shutting pressures).

12 TESTING AND ADJUSTING — Diagnostics and Calibration

The TESTING AND ADJUSTING chapter is the diagnostic heart of the manual. It begins with safety precautions and then walks through adjusting the engine speed sensor, adjusting valve clearance (with firing order and valve arrangement charts), measuring compression pressure (with adapter and gauge tool references), checking and adjusting fuel injection timing (both the match mark method and the delivery valve method, with piston displacement tables for each injection timing), testing and adjusting the fuel cut solenoid, and adjusting the engine stop motor lever. The fuel injection pump calibration data section provides assembly numbers, rack positions, pump speeds, and injection volumes for a wide range of pump configurations covering DENSO NB (EP9), BOSCH PE-P (PS3S), BOSCH PE-P (PS3000), ZEXEL PE-P (PS3S), and ZEXEL PE-6P types. Performance test criteria and run-in standards are also included. The troubleshooting section is extensive, with charts that correlate problems (engine does not pick up smoothly, engine stops during operations, engine does not rotate smoothly/hunting) with causes and remedies, plus check items and questions to guide diagnosis.

13 DISASSEMBLY AND ASSEMBLY — Step-by-Step Procedures

This chapter explains the procedures for removing, installing, disassembling, and assembling each component, along with the precautions that apply to each operation. It is the hands-on reference for engine overhaul work.

14 MAINTENANCE STANDARD — Inspection Judgment Criteria

The MAINTENANCE STANDARD chapter gives the judgment standards for inspection of disassembled parts. Use these values to determine whether a component is within specification or requires replacement or repair.

15 REPAIR AND REPLACEMENT OF PARTS — Component Restoration

This chapter covers the repair and replacement of specific engine components. Procedures include replacing valve seat inserts, replacing the nozzle holder sleeve, replacing the valve guide, replacing the crosshead guide, grinding the valve, grinding of fitting face of cylinder head, replacing cam bushing, replacing cam gear, replacing flywheel ring gear, pressure test, replacing engine rear seal, replacing connecting rod small end bushing, replacing main bearing cap, grinding crankshaft, and replacing the wear sleeve (when equipped with sleeve). Each procedure includes the special tools required and the machining dimensions or tolerances that must be met.

Comprehensive Coverage for Komatsu 125-2 Series Diesel Engines

The Komatsu 125-2 Series Diesel Engine Shop Manual covers engines used across a wide range of Komatsu machinery, including crawler dozers (D53, D58, D60, D65, D70, D75, D85, D87 series), wheel loaders (WA450-3, WA470-3), hydraulic excavators (PC400-6, PC400LC-6, PC450-6, PC450LC-6, HD255-5), mobile crushers (BR500JG-1), and generator sets (EG220BS-2, EG300BS-5, DCA-220SSK, DCA-300SSK, J6D125E-G1-2). Engine performance data, fuel injection pump calibration, and torque specifications are provided for each application variant.

The troubleshooting section alone spans more than 100 pages, giving you diagnostic guidance for problems ranging from poor engine pickup and hunting to abnormal noise, overheating, sudden stoppage, and excessive blow-by. The fuel injection pump calibration data covers a comprehensive range of pump assembly numbers with rack position, pump speed, and injection volume specifications for both service standard and manufacturer standard conditions.

Critical Torque and Specification Data

Engine reliability depends on correct assembly. This manual provides the standard tightening torque tables you need: metric nuts and bolts, split flange bolts, O-ring boss piping joints, O-ring boss plugs, eye joints, tapered screws, and hoses (taper seal and face seal types). Coating materials are also listed, including adhesives, gasket sealants, molybdenum disulphide lubricants, and greases with their Komatsu codes and part numbers. The electric wire code section explains the color and thickness classification system used in the wiring diagrams, and unit conversion tables help when working with metric and imperial measurements.

Why This Manual Matters

When you are rebuilding a 6D125-2, diagnosing a fuel system problem on an S6D125-2, or servicing an SA6D125-2 in a PC400-6 excavator, the difference between a correct repair and a comeback often comes down to having the right specification. Torque values, valve clearances, injection timing, and component wear limits are not guesswork — they are exact figures that Komatsu specifies for these engines. This manual puts those figures in your hands, along with the step-by-step procedures and diagnostic charts to use them correctly.

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This Komatsu 125-2 Series Diesel Engine Shop Manual is delivered as an instant PDF download after payment. There is no shipping, no waiting for a physical book, and no restrictions on where you can use it. Access the manual on any device — laptop, tablet, or smartphone — and print the pages you need for the workshop. Whether you are performing routine maintenance, a full engine overhaul, or troubleshooting a specific fault, the complete service information is available immediately.