Komatsu D20A-6, D20P-6, D20P-6A, D20PL-6, D20PLL-6, D20S-6, D20Q-6, D21A-6, D21E-6, D21P-6, D21P-6A, D21P-6B, D21PL-6, D21S-6, D21S-6A, D21Q-6 Shop Manual (P/N SEBM01040604)

This 493-page PDF factory shop manual serves as the primary technical reference for the Komatsu D20 and D21 series bulldozers, covering the 60001-and-up serial number ranges. It provides a complete contents overview of the OEM documentation needed for shop maintenance and teardown planning. Having these exact specifications on the workbench helps prevent costly parts-swapping and reduces diagnostic time during complex powertrain evaluations. Servicing heavy machinery involves significant physical risks. Always review the factory-specified safety protocols inside the documentation before beginning any mechanical work to prevent injury or equipment damage.

• Covers 1992–2003 Komatsu models: D20A-6, D20P-6, D20P-6A, D20PL-6, D20PLL-6, D20S-6, D20Q-6, D21A-6, D21E-6, D21P-6, D21P-6A, D21P-6B, D21PL-6, D21S-6, D21S-6A, and D21Q-6
• Original OEM publication SEBM01040604 (dated 03–90(01)03381, Printed in Japan)
• Details structural breakdowns, assembly diagrams, and maintenance standards for the 4D95S-W-1 engine and powertrain
• Outlines component teardowns for the fuel injection pump, starting motor, alternator, water pump, thermostat, and nozzle holder
• Explains the final drive, steering brakes, universal joint, main relief valve, damper, and track shoe configurations

Component and System Coverage

This manual documents the exact engineering specifications required to service the 4D95S-W-1 engine. Technicians get a clear look at the powertrain, undercarriage, hydraulic systems, and electrical configurations. Chapters detail the structure and function of the Hydroshift transmission and planetary gear sets. This gives you the context needed for testing, adjusting, and overhauling the main and steering clutch assemblies. It outlines step-by-step instructions for tasks that would otherwise require an expensive dealer visit, such as completing a full engine removal, measuring compression and blow-by pressure, and adjusting fuel injection timing. Comprehensive exploded-view diagrams are included. These cover the track group, bucket lift mechanisms for the S and Q variants, and radiator guard assemblies to speed up parts identification on the shop floor.

Specification and Reference Data

Engine timing and performance values are fully documented for both high and low idle ranges. Intake and exhaust valve clearances are specifically listed for cold-engine settings. To help mechanics maintain factory-grade tolerances during a repair, the text catalogs multi-stage torque values for the cylinder head assembly and injection pump components. Fluid capacities are provided for the engine oil pan, Hydroshift transmission case, and main clutch case. You will also find electrical circuit codes and wire-strand thickness classifications, making it easier to trace electrical faults effectively and apply a reliable fix. To further streamline the workflow, the documentation features essential wiring diagrams, power train hydraulic circuit diagrams, steering hydraulic circuit diagrams, troubleshooting charts, and valve arrangement charts.

When evaluating these 6-series dozers, technicians often overlook that the required modulating valve pressure varies significantly between models—for instance, 27 kg/cm² on the D21A-6 versus 20 kg/cm² on the D21E-6. Furthermore, during engine installation, confusing the mount cushions or failing to verify radial and face runout with a dial gauge frequently leads to severe drivetrain vibration and premature universal joint failure.