1990s Komatsu PW20-1 / PW30-1 Wheeled Excavator Shop Manual (P/N SEBM021F0102)

Komatsu shop manual SEBM021F0102 covers PW20-1 and PW30-1 wheeled excavators, serial numbers 1001 and up. It documents mechanical and hydraulic repair, troubleshooting, and maintenance standards, with engine testing, adjustment, and removal procedures.

• Engine testing and service: Compression and oil-pressure checks, valve-clearance and injection-timing adjustment, fuel-system bleeding, and engine/gear-pump assembly removal and installation.

• Power train repair: Transfer and center-brake disassembly, axle and differential assembly, swing-machinery overhaul, and swing-circle removal and installation.

• Brake service: Fault-finding charts, parking-brake linkage adjustment, circuit bleeding, and removal and installation of master cylinders, calipers, and brake pads.

• Hydraulic diagnosis: Pump-delivery measurement, relief-pressure adjustment, cylinder-leakage checks, and troubleshooting for weak travel, slow work equipment, hydraulic drift, and swing overrun.

• Hydraulic component repair: Travel-motor and swivel-joint disassembly and assembly, hydraulic-cylinder seal work, and inspection standards for pumps and control valves.

• Steering and chassis: Double-articulated steering, suspension-lock operation, steering-cylinder replacement, and pin-and-bushing inspection standards for the chassis and work equipment.

• Electrical documentation: Wiring diagrams, wire-color codes, connector numbering, and switch-connection tables covering starting, charging, lighting, and instrument circuits.

Written for service personnel carrying out workshop repairs, this manual calls for hydraulic test equipment, precision measuring tools, and suitable lifting equipment.

Engine Checks and Repair Coverage

The engine test tables distinguish standard readings from permissible values and specify the conditions needed to interpret them. The compression-test section identifies gauge 795-502-1590 and adapter 795-414-1110.

Injection-timing adjustment is documented through pump-mount shim selection. Engine assembly coverage is limited to removal and installation with the gear pump; this volume does not contain a complete internal engine overhaul procedure.

Axles, Brakes, and Swing Machinery

Axle repair extends to differential disassembly, hub and pinion bearing preload, shim selection, backlash, and gear-tooth contact adjustment. Assembly notes flag the risk of damaging the oil seal when refitting the hub.

Transfer and center-brake procedures cover internal gears, bearings, brake discs, and plates. Separate brake charts address poor braking and brake drag, while the maintenance-standard tables provide wear criteria for caliper pads and rotors.

Swing-machinery overhaul and swing-circle replacement are supported by component views, torque specifications, and clearance limits. Drive-shaft documentation covers universal-joint layout and fastening specifications; the PTO section explains coupling construction and function rather than a complete overhaul.

Always verify component weights against the manual’s hoisting tables and use lifting equipment with sufficient capacity before removing the engine, swing machinery, or axles.

Hydraulic Fault Isolation and Component Work

The hydraulic section connects the triple gear pump and steering-priority valve to the separate control-valve circuits. Its troubleshooting charts distinguish travel faults from steering, boom, arm, bucket, blade, and swing problems.

The cylinder-leakage test helps distinguish hydraulic drift caused by a cylinder from drift caused by the control valve. Pump-flow measurements, relief-pressure checks, and motor-leakage criteria provide further ways to narrow down weak or slow operation.

Travel-motor procedures extend to the piston/drive-shaft assembly, valve plate, bearings, and displacement-control components. Reassembly cautions identify the risk of damaging piston and cylinder sliding surfaces if the assembly is rocked during insertion.

Both the center swivel joint and work-equipment swivel joint have disassembly and assembly coverage. Hydraulic-cylinder procedures address packing direction, piston rings, bushings, and model-specific bucket-cylinder fasteners. The triple gear pump has construction, testing, and maintenance-standard coverage, but no complete internal overhaul procedure.

Circuit Diagrams and Component Views

Brake-control system schematics and wheel-brake section views support brake diagnosis and component identification. Chassis and upper-structure piping diagrams show how the hydraulic lines connect across the machine.

The hydraulic circuit diagram brings the pump, control valves, swivel joints, motors, and cylinders together. The electrical circuit diagram includes connector numbers and switch-connection tables, supported by the manual’s wire-code reference.

Sample Timing, Brake-Wear, and Lubrication Data

Injection timing: The 3D84-1H and 3D84-1J engine specifications list 19° before compression TDC. The adjustment section relates a 0.1 mm change in pump-mount shim thickness to approximately 1° of timing change.

Brake wear: The wheel-brake inspection table gives 10.0 mm as the standard remaining friction-material thickness and 2 mm as the repair limit.

Swing lubrication: The swing machinery case has a 1.5-liter specified capacity and the same refill capacity, listed alongside lubricant selection by ambient temperature.

PDF Search, Diagram Viewing, and Included Pages

Search and diagram access: PDF text search is unavailable. Embedded bookmarks are mostly unlabeled and do not provide useful chapter names. Small wiring and hydraulic-diagram labels require zooming; the large-format sheets are stored sideways and benefit from rotating the view.

Supplied as one printable, 230-page PDF, including the cover, two revision-list pages, and 13 blank pages. Four large-format piping and circuit-diagram sheets are included at the end of the same file.