Komatsu D20PL-7, D20PLL-7, D20AG-7, D20P-7A, D20PG-7A, D21A-7, D21AG-7, D21PG-7A, D21S-7, D21QG-7, D21A-7T Bulldozer & Loader Shop Manual (P/N SEBM001408)

This Komatsu shop manual, P/N SEBM001408, is the February 2008 revision for the D20 and D21 Dash-7 dozers and dozer shovels listed above. It includes a dedicated D21A-7T trimming-dozer section.

Bookmarked PDF and Wiring Diagram Detail

Search, navigation and diagram labels: Embedded bookmarks provide access to chapters and individual components. Text search is limited to the four revision-list pages; the technical chapters are not text-searchable. Small wiring labels require zooming.

One printable 716-page PDF, including the original cover, contents page, four revision-list pages and 51 blank pages. These pages are already included in the total.

Power Train Overhaul and Hydraulic Fault Diagnosis

The following selected workshop topics show the manual’s repair coverage. Other subjects include engine-stop cable adjustment and push-pull coupler handling.

• Engine testing: Compression and blow-by measurement, valve-clearance adjustment, fuel-injection timing checks, fuel-circuit bleeding and engine oil-pressure testing.

• Transmission repair: Step-by-step removal, disassembly and assembly procedures for the D20 main clutch and transmission, plus the D21 HYDROSHIFT transmission.

• Steering and final drives: Steering-clutch overhaul, PPC valve service, brake adjustment, bevel gear shaft installation and final-drive disassembly and assembly.

• Work-equipment hydraulics: Main-relief pressure testing, steering and cylinder bleeding, control-valve overhaul, and blade or bucket cylinder removal and repair.

• Undercarriage service: Track-frame removal, recoil-spring service, idler and roller overhaul, with separate maintenance standards for steel tracks and rubber crawlers.

• Electrical reference: Serial-specific wiring diagrams, cab circuits, engine-stop and starting-safety mechanisms, monitor functions and sensor test specifications.

Written for service technicians performing workshop repairs, the manual includes procedures requiring hydraulic test equipment, lifting equipment and component-specific special tools.

Engine Testing, Fuel Equipment and Cooling

Engine troubleshooting charts address hard starting, low output, abnormal exhaust, overheating and oil-pressure problems. The matrix format connects symptoms, preliminary checks and probable causes, supporting fault isolation before major assemblies are dismantled.

Removal and installation instructions cover the fuel-injection pump, nozzle holders, cylinder head, water pump, thermostat, radiator and complete engine assembly. The cover refers detailed engine information to the separate 95 Series and 94 Series Engine Shop Manuals, which are not included in this download.

Clutches, HYDROSHIFT and Bevel Gears

Power train skeleton drawings and hydraulic circuit diagrams explain the relationship between the transmission pump, control valves, clutches and lubrication circuits. Modulating- and inching-pressure checks provide diagnostic context for slow travel, delayed engagement and shifting complaints.

The repair chapters extend to carrier assemblies, clutch packs, modulating valves, and selector and inching valves. Bevel gear installation includes bearing preload, backlash and tooth-contact adjustment; maintenance-standard tables provide inspection criteria for disassembled parts.

The D20 transmission instructions warn that a bearing can damage an adjacent gear during removal. The D21 transfer-assembly instructions identify possible bearing-cage damage from using forcing screws to extract the cage from the pinion shaft.

Hydraulic Equipment and Track Assemblies

Separate circuit diagrams cover the straight tiltdozer, power angle and tiltdozer, and dozer-shovel arrangements. Hydraulic drift and lifting-force troubleshooting distinguish possible pump, valve, cylinder and linkage faults.

Cylinder assembly instructions address rod packing, dust seals, O-rings and piston components. Undercarriage references distinguish lubricated track links, dry track links and rubber crawlers, with serial-specific roller designs and associated wear limits.

Operating on and servicing heavy equipment carries inherent physical risks; always establish proper workshop safety protocols and relieve system pressure before beginning mechanical work.

Wiring, Monitor Functions and Workshop References

The chassis electrical wiring diagrams and cab electrical circuit drawings are supported by an electric wire code table covering wire size, current rating, circuit application and color codes. Monitor-system references explain the gauges and warning lamps, while sensor tables provide electrical judgment values.

Standard tightening-torque tables cover metric fasteners, flared nuts, split flanges and O-ring boss fittings. Pressure conversion tables, assembly weights and lubricant charts support workshop preparation. The fluid charts distinguish specified capacity from refill capacity and show lubricant selection by ambient temperature.

D21A-7T Trimming-Dozer Section

Section 90 supplies trimming-dozer specifications, power train and work-equipment hydraulic circuit diagrams, transmission-control details, wiring diagrams and maintenance standards. It covers the trimming cylinder, blade mounting and related clearances, and directs shared machine information back to the main D20/D21 chapters.

Examples of Valve-Clearance and Sensor Specifications

For D21A-7 and D20P-7A machines with serial numbers 75001–78603, the valve-adjustment chapter specifies cold clearances of 0.35 mm for intake valves and 0.50 mm for exhaust valves.

The fuel-level sensor table lists approximately 10 Ω at full and 80 Ω at empty, at a normal temperature of 25°C, with the starting switch ON as the stated measurement condition.