Komatsu PC20-6 / PC30-6 / PC40-6 — 1989 Mini Excavator Shop Manual (P/N SEBM020R0604)

Komatsu shop manual P/N SEBM020R0604 covers the 1989 PC20-6, PC30-6, and PC40-6 mini excavators, with separate procedures and diagrams for the serial-number changes listed above.

PDF Bookmarks, Diagram Detail and Page Count

Navigation and legibility: Embedded bookmarks link to the main sections and individual procedures. PDF text search is not available. Small wiring labels require zooming; some pressure labels in the PC40-6 hydraulic circuit diagram on PDF p. 35 remain faint and partly illegible even when enlarged.

Supplied as one printable English PDF with 345 pages, including the original cover and two revision-list pages. Revised and inserted service pages are included in this total.

Hydraulic Testing, Travel Drive Repair and Chassis Service

The following selected workshop topics outline the manual’s coverage. Additional subjects include floor-frame removal and installation and component weight tables for handling assemblies.

• Hydraulic diagnosis: Pump discharge measurement, relief-pressure testing and adjustment, motor leakage tests, and fault charts for weak movement, hydraulic drift, and travel deviation.

• Travel and swing assemblies: Step-by-step disassembly and assembly of travel motors, reduction gears, swing machinery, swing motors, and the center swivel joint.

• Engine service: Valve-clearance adjustment, compression testing, fuel-injection timing, and removal and installation of engines, cylinder heads, and nozzle holders.

• Undercarriage: Track shoe, sprocket, track roller, and idler removal and installation, plus recoil-spring disassembly, assembly, and inspection standards.

• Work equipment and cylinders: Boom, arm, bucket, and blade removal, hydraulic-cylinder rebuilding, piston-ring replacement, and cylinder air-bleeding procedures.

• Electrical reference: Serial-specific wiring diagrams, wire-color codes, and switch connection tables, together with starter and alternator removal and installation.

Written for service personnel carrying out workshop repairs, the manual calls for hydraulic test equipment, lifting gear, and special tools for the relevant operations.

Hydraulic Fault Isolation and Component Inspection

The power-train and hydraulic triple gear pump sections explain how pump output feeds the machine’s working circuits. Section views of the pump and multi-spool control valves identify internal components, while hydraulic circuit schematics show their connections.

The diagnostic tables provide a baseline for interpreting machine symptoms and test results. For travel deviation, the center swivel joint tests distinguish internal joint leakage from a travel-motor fault; cylinder leakage tests distinguish cylinder faults from control-valve leakage.

Control-valve coverage: The PC20-6 uses a 2-spool valve alongside the 6-spool valve; the PC30-6 and PC40-6 sections include the 3-spool arrangement. PC40-6 circuit diagrams also cover additional-equipment and breaker configurations, without providing a breaker overhaul procedure.

The maintenance-standard tables give inspection dimensions, clearance limits, and repair criteria for the covered components. Before inspecting high-pressure hydraulics or structural components during any repair, always follow standard shop safety protocols to prevent injury.

Travel Motors, Swing Machinery and Undercarriage

Travel-motor cross-sections and separate overhaul sequences distinguish the earlier and later assemblies. The earlier units include bearing-preload and axial-clearance checks; the later procedures cover planetary carriers, sun gears, floating seals, and brake valves.

For the early PC20-6 travel motor, the manual warns that insufficient internal thrust clearance can cause seizure, while excessive clearance causes leakage and poor operation.

Swing-circle inspection, swing-machinery backlash checks, and track-frame repair criteria extend the coverage beyond removal instructions. Track shoe and roller tables distinguish standard dimensions from wear limits.

Engine, Cooling and Electrical Scope

The 3D84 and 3D95S-W engine sections distinguish the applicable valve and injection-timing procedures. Cooling-system work includes water-pump, radiator, and hydraulic oil-cooler removal and installation.

Engine overhaul scope: This volume covers the engine work listed above; it does not include a complete internal engine overhaul manual. Komatsu’s separate engine volumes are not included.

The electrical diagrams map starting, charging, lighting, instruments, and cab equipment. Their wire codes and switch connection tables support circuit tracing, with separate drawings for the documented electrical serial breaks.

Fluid Capacity and Pump Wear Examples

The oil and coolant tables list a 5.0-liter cooling-system capacity for the PC20-6 and PC30-6.

For the PC40-6, hydraulic oil capacity is 60 liters for the complete system, including components and piping, with a 45-liter refill quantity.

The PC20-6 and PC30-6 triple gear pump inspection table specifies side clearance between the gear case and gear of 0.10–0.15 mm, with a 0.19 mm clearance limit.