Komatsu D20A-6, D20P-6, D20PL-6, D20PLL-6, D21A-6, D21E-6, D21P-6, D21PL-6, D20P-6A, D21P-6A, D21P-6B Operation and Maintenance Manual (P/N SEAM01010601)

• Covers 1980s–1990s Komatsu D20 and D21 series bulldozers, including D20A-6, D20P-6A, D21E-6, and D21P-6B variants
• Original Komatsu publication SEAM01010601, aligned with the 60001 and up serial number range
• Details 56 individual maintenance and adjustment procedures supported by 121 pages of technical schematics and illustrations
• Documents essential lubrication schedules, adjustment metrics, and pre-start inspection guidelines
• Features essential PDF diagnostic routines and troubleshooting protocols to streamline complex machinery repairs
• Highlights critical service steps for the water separator, main clutch, transmission, bevel gear case, and final drive

Operational and Maintenance Coverage

This reference material breaks down daily machine handling, cold weather start procedures, and periodic service intervals. It maps out instrumentation locations alongside control lever functions and gear shifting patterns. Operators will find detailed undercarriage care instructions. To help independent mechanics and DIYers bypass expensive dealer repair bills, the manual provides crucial step-by-step instructions for tasks like bleeding air from the fuel injection pump, measuring track link pitch, and adjusting the main clutch. The text clearly outlines the lubrication schedule. It provides point-by-point grease fitting diagrams for both the hydraulic tilt dozer and angle-tilt frame components. Maintenance interval charts span 50 to 4000 hours, listing specific required actions like filter replacements, cooling system flushes, and engine valve clearances for the Komatsu 4D95S-W-1 diesel engine.

Technical Data and Shop Utility

Factory specifications highlight operating weights, travel speeds, and cooling system capacities. Exact fuel, oil, and coolant grades are mapped out for varying ambient temperature ranges. To support these procedures, the document incorporates specific gravity conversion tables, oil filler and level gauge position views, fuse arrangement circuits, and track shoe tightening sequence drawings. Mechanics will find precise torque values throughout. For example, multi-stage cylinder head bolt sequences include final-stage angles of 180° ± 10°. Track shoe bolt torque data mandates 7 ± 1 kgm plus an additional 60° ± 10° tightening angle. Fluid capacities are explicitly stated, including the 21-liter hydraulic tank limit for the D20A-6 variant. Steering lever travel limits are mapped at 200–274 mm in the adjustment tables. Having these exact factory baselines directly on the shop floor accelerates turnaround times and eliminates unnecessary guesswork during routine service.

When evaluating these older Komatsu dozers, technicians often encounter accelerated track idler wear caused by neglecting the strict 1.0 mm shim clearance tolerances. Another common pitfall is failing to properly bleed the tilt and angle cylinder circuits after hydraulic maintenance, which routinely leads to a spongy blade response. Addressing these issues with precise factory metrics prevents extensive secondary component failures. Executing these procedures demands strict adherence to factory limits. Always secure the machine on level ground and consult the complete OEM specifications before initiating hands-on work to maintain safe operating standards and prevent equipment damage.