Komatsu PC128US-2, PC138US-2 & PC138USLC-2 Excavator Service Manual – 2004 (P/N SEBM018417)

Komatsu shop manual P/N SEBM018417 (May 2004 revision) covers PC128US-2, PC138US-2, and PC138USLC-2 excavators, with procedures distinguished by serial number and equipment. Detailed internal engine servicing requires the separate 102 Series and 95 Series Engine Shop Manuals, which are not included.

PDF Text Search and Diagram Navigation

Search and navigation: Text search is available in many sections, but some pages and schematics lack searchable text. Bookmarks cover chapters and procedures; the legacy Main Menu target is not included. Small wiring labels require zooming, and some remain faint.

One printable English-language 1,028-page PDF, including one cover page, five revision-list pages, and 35 blank pages.

Hydraulic Tests, Fault Diagnosis, and Component Repair

These selected coverage highlights outline the workshop tasks documented in the manual. Other sections include bonded cab-glass replacement and air-conditioning component removal.

• Hydraulic diagnosis: Main-pump, PC/LS valve, pilot-circuit, and solenoid pressure tests, plus work-equipment drift checks and hydraulic air bleeding.

• Control valves and cylinders: Step-by-step disassembly and assembly of control-valve sections, PPC valves, relief valves, and boom, arm, bucket, and blade cylinders.

• Swing and undercarriage: Swing-machinery overhaul, center-swivel service, recoil-spring and idler assembly work, and track-roller and track-shoe procedures.

• Engine and cooling service: Valve-clearance and injection-timing adjustments, engine-and-pump removal, and radiator, oil-cooler, and aftercooler replacement procedures.

• Electrical troubleshooting: Serial-specific fault charts, CR700 controller diagnosis, monitor service codes, connector pin tables, and circuit checks.

• Workshop references: Hydraulic and electrical schematics, component section views, special-tool lists and sketches, torque specifications, and wear-limit tables.

Written for service personnel performing workshop repairs, this manual assumes access to hydraulic test equipment, electrical meters, lifting gear, and the specified special tools.

Serial-Specific Controls and Electrical Diagnosis

Earlier PC128US-2 controls differ from the CR700 arrangements used from serial 7731. The electrical sections distinguish monitor faults, controller communication, engine deceleration, pump control, and input-signal problems.

Monitor-panel procedures cover stored service codes, live input/output readings, governor-motor adjustment, and PC-EPC and LS-EPC current adjustment. Diagnostic charts connect faults to connector measurements and component checks, including separate paths for short circuits and disconnected wiring.

Hydraulic Fault Isolation and Internal Repair

CLSS operating explanations cover load sensing, pressure compensation, swing control, and drift prevention. The hydraulic-drift test distinguishes cylinder leakage from control-valve trouble, helping identify which assembly needs further inspection.

Valve and cylinder chapters extend into internal assembly, seal placement, and inspection criteria. Center-swivel instructions specifically caution that rotor installation can damage the slipper seals and O-rings.

Mechanical Work and Engine Diagnostics

Swing-machinery procedures address bearings, planetary carriers, and gear assembly. Undercarriage inspection standards distinguish early and later idlers, track rollers, and track shoes; these differences matter when comparing a removed component with its wear limits.

Engine testing includes blow-by and oil-pressure measurements, with symptom-based diagnosis for difficult starting, smoke, low power, and overheating. The SAA4D95LE-3-A versions also receive cylinder-head and injection-pump removal and installation procedures.

Raised work equipment, residual hydraulic pressure, and heavy assemblies require the support, isolation, and lifting precautions specified in the manual.

Circuit References and Workshop Tools

The Overall System Diagram and Connector Arrangement Diagram map control components and harness connections. Hydraulic Circuit Diagram sheets for blade-plus-attachment configurations and Electric Circuit Diagram sheets for KUK specifications distinguish attachment plumbing and regional wiring.

T-adapter tables identify connections for electrical testing. Dimensioned sketches accompany the special-tool list for locally made push tools, wrenches, and adapters.

Valve-Clearance Examples by Engine

For the S4D102E-1 in the PC128US-2 and PC138USLC-2 serials 1001–1500, valve clearances at normal temperature are 0.25 mm intake and 0.51 mm exhaust.

For the SAA4D95LE-3-A in the PC138US-2 and PC138USLC-2 serials 1501 and up, the corresponding specifications are 0.35 mm intake and 0.50 mm exhaust. Separate adjustment procedures accompany these engine-specific values.