1993 Komatsu 3D72-2, 3D75-2, 3D78-1, 3D84-2, 3D84N-2, 4D84-2 Diesel Engine Shop Manual (P/N SEBM002400)

This Komatsu shop manual, publication SEBM002400, November 1993 edition, covers 3D72-2, 3D75-2, 3D78-1, 3D84-2, 3D84N-2, and 4D84-2 engines. The opening application chart identifies their TN-series equivalents. Additional TN-engine material is organized by model and application specification.

• Internal engine repair: Cylinder-block and cylinder-head inspection, piston and pin measurements, connecting-rod alignment, crankshaft checks, timing-gear service, and engine disassembly and reassembly.

• Fuel injection equipment: YPES and YPFR pump teardown, governor inspection, injection-timing and delivery adjustments, feed-pump service, and hole-type and pintle-type nozzle testing.

• Lubrication system: Oil-flow diagrams, trochoid-pump inspection, filter and pressure-control-valve service, plus oil-cooler and piston-cooling-nozzle coverage for specified turbocharged variants.

• Cooling system: Radiator and cap pressure tests, fan-belt adjustment, thermostat and thermoswitch checks, and water-pump disassembly and mechanical-seal inspection.

• Air induction and turbochargers: Air-cleaner maintenance, IHI turbocharger disassembly and reassembly, wastegate checks, rotor-clearance measurements, and fault-tracing charts.

• Electrical service: Wiring diagrams, conventional and reduction-type starter repair, alternator and magneto-generator checks, starting-aid circuits, and battery testing.

This manual is written for workshop service personnel; injection-pump calibration calls for a dedicated pump test stand.

Internal Engine Inspection and Timing

Block inspection includes dye-penetrant crack testing and bore measurements at several positions. Sleeveless-cylinder repair covers Flex-Hone selection, reboring, and a calculation diagram for obtaining the crosshatch angle.

Crank-pin oil-clearance checks use Plastigage. The cylinder-head material covers valve-seat correction, guide replacement, valve-spring inspection, and staged head-bolt tightening. Piston and cylinder identification marks help match components before assembly.

The flywheel and crankshaft-pulley sections distinguish balanced components from designs with intentional unbalance masses. Timing-gear inspection notes link excessive backlash to gear damage and incorrect valve or injection timing.

This is an engine volume; chassis and attachment service requires the corresponding machine volumes.

Injection-Pump Testing and Fuel Diagnosis

Pump identification: The 3TNA72E uses YPFR equipment; the other listed Komatsu engine equivalents use YPES equipment. Their procedures include plunger and delivery-valve pressure tests, cylinder-to-cylinder delivery checks, and governor adjustment with the applicable torque-rise devices.

The tool listings identify equipment such as rack indicator 158090-51500 and top-clearance gauge 158090-51300. Fuel-system troubleshooting separates supply, nozzle, timing, and pump faults before pump removal, helping narrow down hard starting, rough idle, and insufficient output.

Application-specific limits: Section 90 expressly separates engine-condition checks from changes to pump output settings. Its 3TNC78E-VM / PC10-7 test-data columns are blank; general specifications and repair material for that engine family appear elsewhere in the book.

Lubrication and Cooling Service

Oil-flow diagrams explain how the filter, pressure-control valve, bearings, and injection pump receive lubricant. The trochoid-pump cover is removable, but the manual directs assembly replacement rather than disassembly of the rotor, shaft, and drive gear.

The Cooling Water Circuit and component views support radiator leak testing, thermostat checks, and water-pump repair. Oil-cooler and piston-cooling-nozzle material is assigned to specified turbocharged TN applications.

Air-Cleaner and Turbocharger Work

Air-cleaner coverage includes element inspection and cleaning precautions. The turbocharger chapter distinguishes IHI RHB31 and RHB51 units, with a wastegate-system exploded view, actuator checks, and axial and radial rotor-play measurements.

Turbocharger fault trees address oil leakage, insufficient boost, abnormal noise, and wheel-to-housing contact.

Starting and Charging Diagnosis

The Wiring Diagram Optional List matches circuit configurations to engine families and installed equipment. The Troubleshooting for Starting Motor chart follows no-crank faults through battery, wiring, relay, magnetic-switch, and motor checks.

Alternator service includes diode, rotor, stator, brush, and IC-regulator tests. Its precautions explain how high-voltage insulation testing can burn out the diodes and regulator.

Follow the manual’s precautions for lifting engine assemblies, electrical isolation, and hot or pressurized circuits.

Valve Clearance and Crankshaft Endplay: Sample Data

These examples are a small selection of the manual’s adjustment and inspection data. Cold intake and exhaust valve clearance is specified at 0.2 mm (0.0079 in.).

For the 3TNA72E, the crankshaft inspection table lists a standard side gap of 0.09–0.271 mm and a wear limit of 0.33 mm, distinguishing the normal assembly range from the replacement threshold.

PDF Bookmarks, Diagram Viewing, and Page Count

Search, navigation, and wiring detail: PDF text search is not available. Embedded bookmarks provide chapter and subsection navigation. Small wire and connector labels on the checked wiring pages are readable after rotating and enlarging the view.

Supplied as one printable English PDF with 262 pages total. This includes the cover and 15 preliminary pages containing contents, safety information, the foreword, and reference tables; these pages are already included in the total.