1994+ Komatsu PC50UU-1 Mini Excavator Shop Manual (P/N SEBM020U0104)

This Komatsu shop manual covers the 1994 and newer PC50UU-1 mini excavator equipped with the 3D95S-W-1 engine, serial numbers 1001 and up. The publication is SEBM020U0104, revision 4.

Text search and diagram navigation: PDF text search is not available. Embedded bookmarks link to the four main technical sections and individual repair topics. Small wire codes and connector numbers in the electrical diagrams require zooming.

• Engine testing: Valve-clearance adjustment, compression-pressure measurement and fuel-injection timing, with the related engine test specifications and equipment requirements.

• Hydraulic diagnosis: Main relief-pressure testing and adjustment, plus internal leakage checks for cylinders, swing and travel motors, and the center swivel joint.

• Component repair: Hydraulic-pump removal and installation, plus disassembly and assembly of control valves, main relief valves, swing machinery, center swivel joints and hydraulic cylinders.

• Undercarriage and work equipment: Idler, recoil-spring, track-roller and track-shoe service, plus removal and installation of the boom, arm, bucket and blade assemblies.

• Electrical circuits: Serial-specific wiring diagrams, connector numbers, wire codes and starting-switch connection tables, including circuits for machines equipped with an operator's cab.

• Workshop reference: Special-tool lists, tightening-torque tables, fluid-capacity data, inspection clearances and wear limits for the covered assemblies.

Written for service technicians performing workshop repairs, the manual includes procedures that require hydraulic test equipment, lifting gear and dedicated component tools.

Engine Service and Repair Scope

Removal and installation procedures cover the engine and cylinder head, along with the fuel injection pump, nozzle holders, starting motor and alternator. Cooling-system work includes the radiator, water pump and thermostat.

Fuel-system bleeding and injection-timing checks accompany the relevant installation work. For detailed engine work, Komatsu directs the reader to the separate 95 Series Engine Shop Manual; this machine manual does not contain a full internal engine overhaul section.

Hydraulic Diagnosis and Component Repair

The KHP-14+14+10 hydraulic pump, 6-spool and 3-spool control valves, and safety-suction valves are described alongside the M25 swash plate axial piston swing motor. The Power Train and Hydraulic Circuit Schematics drawings show how these components connect to the travel drives and work equipment.

The GM05V travel-motor sections explain reduction-gear and brake-valve operation, with removal and installation procedures for the motor assembly.

Fault isolation: Thirteen symptom-based diagnostic tables cover weak or inoperative work equipment, excessive swing drift, swing overrun and travel deviation. The cylinder leakage test helps distinguish internal cylinder leakage from a control-valve fault before repair decisions are made.

Swivel-joint diagnosis links leakage checks to individual ports when travel is slow or uneven. The assembly instructions warn that incorrect rotor installation can damage the slipper seals and oil-seal lip.

Cylinder rebuilding: Procedures cover the cylinder head, rod packing, dust seals, piston rings and wear rings. The tool list identifies cylinder repair stand 790-502-1003 and piston-ring expander 790-720-1000. Assembly cautions address press-fitting errors that can deform the cylinder-head bushing.

Serial Changes, Undercarriage and Wiring

S/N 2313: Separate track-frame, idler and track-roller drawings and maintenance standards distinguish early and later undercarriages.

S/N 3401: Hydraulic Circuit Diagram and Electrical Circuit sheets separate machines through S/N 3400 from later machines. The later hydraulic arrangement adds a check valve and slow-return valve, and its travel/boom acceleration circuit differs from the earlier travel-acceleration circuit.

The later electrical diagram shows a timer, relay and glow-plug circuit, plus cab wiring for the wiper, washer, heater, radio and room lamp. These distinctions help match the circuit sheet to the machine before tracing a fault.

Mechanical repair coverage extends to swing-circle removal, recoil-spring disassembly and the separate boom sections. Work Equipment section views and maintenance tables identify pin-and-bushing clearances; Swing Machinery views pair gear and spline inspections with wear limits.

Service Specifications and Workshop Precautions

The reference tables distinguish specified total capacities from routine refill quantities, including engine-oil capacity changes at S/N 2646 and 3401. They provide coolant-capacity data, hydraulic cylinder strokes and rod diameters, relief-pressure specifications for the boom, arm, bucket and swing circuits, and general bolt-and-nut torques in kgm and Nm.

Pressurized hydraulics, loaded recoil springs and heavy assemblies require the safety precautions and lifting arrangements specified in the OEM service publication.

PDF Contents and Page Breakdown

One printable 189-page PDF: 14 preliminary pages, 40 pages of Structure and Function, 44 of Testing and Adjusting, 72 of Disassembly and Assembly, and 19 of Maintenance Standard. The cover, revision list and 18 numbered technical insert pages are already included in this total.