Komatsu D20, D21A, P, PL Bulldozer Factory Shop Manual (P/N C4085-91017)

• Covers 1985–2021 Komatsu D20A-5, D20P-5, D20PL-5, D21A-5, D21P-5, and D21PL-5 bulldozer configurations with serial numbers 45001 and up
• Official OEM publication form 00-001, printed May 1981
• Includes 103 detailed component exploded-view diagrams, 4 hydraulic system schematics, and 12 tolerance specification tables
• Serves as the primary reference for the 45000-series D20 and D21 build, providing foundational engine and powertrain specifications for the -5 generation models

Component Structure and Maintenance

Working on heavy machinery requires exact specifications, and this manual delivers the technical descriptions needed for the bulldozer chassis, engine, powertrain, undercarriage, and hydraulic systems. It breaks down major component groups by structure and function to help you efficiently identify and diagnose issues in the shop. You will find comprehensive coverage comparing the direct transmission to the Hydroshift transmission. The text also digs into the mechanics of the main clutch, inertia brake, and steering clutch components. Understanding how the steering control valve interacts with the hydraulic circuits is vital for maintaining optimal tractor performance. When servicing these high-pressure hydraulic circuits or heavy mechanical assemblies, always refer to the factory torque and relief valve thresholds before loosening fittings to prevent component failure or severe injury.

Technical Specification Preview

Factory data leaves no room for guesswork. The guide fully documents engine specifications for the 4D94-2N and 4D94-2P powerplants, highlighting the 2,940 cc displacement and 39 HP output at 2,450 rpm. It outlines engine lubrication and cooling parameters, noting a standard coolant capacity of 13.0 to 13.6 liters. In the cylinder head specification tables, intake and exhaust valve clearance is set at 0.3 mm. Fuel injection timing is calibrated to 16° before top dead center, while the torque specification for the fuel injection pipe sleeve nut is strictly 7.25 ± 0.25 kg.m. To simplify shop work, the publication features extensive tolerance charts. These tables detail standard sizes alongside repair limits for engine, transmission, and final drive components, providing the critical technical depth required for professional-grade service on the 45000-series machines.