1985– Komatsu D20A-5, D20P-5, D20PL-5, D21A-5, D21P-5, D21PL-5 Bulldozer Chassis Shop Manual (P/N SEBM0101D00)

Komatsu chassis shop manual SEBM0101D00, printed May 1981, covers 1985– D20A-5, D20P-5, D20PL-5, D21A-5, D21P-5, and D21PL-5 bulldozers. Cover serial ranges start at 45001 for A/PL models and 45003 for P models.

Supplied as a single 223-page PDF in English.

• Engine testing: Compression and blowby measurements, valve-clearance adjustment, exhaust smoke testing, and lubrication and cooling-system checks.

• Fuel system: Injection-pump inspection, nozzle spray and pressure tests, fuel-injection timing adjustment, and fuel-circuit air bleeding.

• Powertrain: D20 direct-transmission and D21 Hydroshift operation, clutch and brake adjustments, oil-pressure tests, and component inspection standards.

• Hydraulics: Blade-control valve operation, relief-pressure testing, work-equipment drift measurement, and angle-cylinder head-circuit bleeding.

• Undercarriage and blade: Track-frame, recoil-spring, idler, roller, and track-shoe wear standards, plus blade linkage and mounting-joint inspection data.

• Technical illustrations: Engine performance curves, general assembly drawings, Hydroshift transmission hydraulic diagrams, steering hydraulic circuits, and work-equipment section views.

Written for service workshop personnel, this manual uses pressure-testing equipment and other dedicated measuring tools for its diagnostic procedures.

Engine Inspection and Fuel-System Testing

Engine coverage distinguishes the 4D94-2N in the D20 from the 4D94-2P in the D21. Compression-pressure testing addresses suspected piston, piston-ring, or cylinder-liner wear; exhaust-color measurement uses a smoke meter.

Bosch PES-A injection-pump checks cover the control linkage, rack, plunger, and delivery function; final pump assessment calls for a test bench. Cooling coverage includes coolant-temperature measurement and fan-belt adjustment, while lubrication checks address oil pressure, temperature, deterioration, and contamination.

D20 Direct Drive and D21 Hydroshift

The text explains the D20 main clutch and inertia brake alongside the D21 damper, universal joints, planetary gear mechanisms, modulating valves, and quick return valves. Testing sections distinguish Hydroshift modulating pressure, inching-valve pressure, and steering-clutch piston pressure.

Steering-brake, parking-brake, inching-pedal, and main-clutch adjustments are supported by lever-travel and operating-force checks. Maintenance tables give standard sizes, repair limits, gear backlash, spring loads, and component-specific tightening torques for the transmission, bevel gear shaft, steering clutches, and final drive.

Blade Hydraulics and Serial-Specific Layouts

Blade configurations: A models use hydraulic angle and tilt control; P/PL models use the tilt-dozer arrangement. Later piping drawings start at D20A-5/D20PL-5 serial 50001, D21A-5/D21PL-5 serial 50002, D20P-5 serial 50004, and D21P-5 serial 50006.

These serial-specific drawings help match the installed piping before investigating blade drift or selecting the relevant pressure-test circuit. The hydraulic sections identify the 790-301-1103 hydraulic tester and 790-500-1300 thermistor kit used for pressure and temperature measurements.

Incorrect main-relief adjustment can expose the pump and connected components to excessive pressure; the valve explanations distinguish this protection from the actuator-side safety and suction valves. Hydraulic testing involves pressurized oil and moving equipment; follow the manual's safety precautions.

Undercarriage and Component Repair Standards

Track-frame drawings distinguish the construction through serial 50000 from serial 50001 onward. Inspection tables cover recoil springs, idlers, track rollers, carrier rollers, track shoes, and sprocket wear, with standard dimensions and repair limits for assessing parts during repair.

Work-equipment tables distinguish A-model blade joints from P/PL arrangements, including cylinder pins, bushings, trunnions, cutting edges, and end bits. Some D21 component-weight and fluid-capacity tables use narrower starting serials: D21A-5 45005, D21P-5 45007, and D21PL-5 45013.

Chassis Volume and Repair Coverage

This file contains structure/function, testing/adjusting, and maintenance-standard sections. It does not include dedicated disassembly/assembly chapters, full internal engine-overhaul instructions, or electrical wiring diagrams; the separate engine, fuel-system, and electrical volumes referenced in the foreword are not included.

Network diagrams and the “Diagnoses”/“Causes” troubleshooting chart appear as format examples in the foreword, rather than a dedicated model-specific troubleshooting section.

PDF Navigation and Diagram Readability

The page total includes one cover, nine safety/foreword/contents pages, and 213 chapter pages, including section dividers. Embedded bookmarks provide section navigation, but PDF text search is unavailable. Small hydraulic labels need zooming; some Hydroshift clutch labels remain faint and difficult to read even when enlarged.