Within the hour you could have this Komatsu PC78US-6, PC78UU-6 shop manual PDF open beside the machine, checking bucket pin wear against factory limits: 785 pages of service data issued under OEM ID SEBM025109 covering both hydraulic excavator variants. Troubleshooting takes up the largest share of the book, organized by Komatsu's own diagnostic modes, from governor and pump control faults to travel deviation and hydraulic drift, each traced to a cause. Full hydraulic and electrical circuit diagrams sit at the back, and the disassembly section walks the main pump, cylinder head, and counterweight off and back on. Check arm and bucket pin-to-bushing clearance against the 0.105 to 0.233 mm limit, then torque the track frame idler cushion bolts to 186 to 225 Nm. A guessed pressure figure can cost you a rebuilt pump. Bookmarked and text-indexed, this PDF puts the H-mode drift chart two clicks away.
What's Inside This Komatsu PC78US-6, PC78UU-6 Manual
| System | Pages | Key Topics |
|---|
| General | 27-47 | Specification Dimensions Drawing, Specifications, Weight Table |
| Structure and Function, Maintenance Standard | 48-275 | Power Train System, Swing Circle, Swing Machinery, Track Frame and Idler Cushion |
| Standard Value Tables | 276-293 | Engine Standard Values, Chassis Standard Values, Electrical Parts Standard Values |
| Testing and Adjusting Procedures | 294-335 | Engine Speed Measurement, Exhaust Gas Color, Valve Clearance, Compression Pressure, Fuel Injection Timing, Track Shoe Tension |
| Troubleshooting - General and Communication | 336-417 | Troubleshooting Sequence, Connector Handling, Communication System (N Mode) |
| Troubleshooting - Controller (Governor and Pump Control) | 418-502 | Governor Control System (E Mode), Pump Control System (C Mode), Engine Start/Stop Issues |
| Troubleshooting - Input Signal System (F Mode) | 503-511 | Swing Pressure Switch, Travel Pressure Switch, Boom Raise Pressure Switch, Arm in Pressure Switch |
| Troubleshooting - Hydraulic and Mechanical Systems (H Mode) | 512-577 | Work Equipment Speed/Power, Swing Speed/Power, Travel Deviation, Hydraulic Drift |
| Troubleshooting - Machine Monitor System (M Mode) | 578-608 | Monitor Panel Display, Wiper System, Washer Motor, Fuel Level Sensor, Coolant Temperature Sensor |
| Disassembly and Assembly | 609-689 | Counterweight Assembly, Injection Pump Assembly, Cylinder Head Assembly, Main Pump Assembly |
| Other Specifications (PC78US-6 for Norway) | 690-767 | Norway Specification Dimensions Drawing, Norway Specifications, Norway Weight Table |
| Others | 768-785 | Hydraulic Circuit Diagram, Electrical Circuit Diagram |
Quick Reference Specifications
| Specification | Value | Page |
|---|
| Torque for track frame and idler cushion bolts | 186 - 225 Nm | p. 56 |
| Hydraulic pump bolt torque (PEN, PDA, PM, PD) | 7.8 - 9.8 Nm | p. 95 |
| Hydraulic pump bolt torque (Ppls, P1T, P1) | 11.8 - 19.6 Nm | p. 95 |
| Clearance between mounting pin and bushing of arm and bucket | 0.105–0.233 mm | p. 201 |
| Clearance between mounting pin and bushing of bucket and link | 0.131–0.245 mm | p. 201 |
| Clearance between mounting pin and bushing of boom and arm | 0.130–0.274 mm | p. 201 |
| Clearance between 1st boom and 2nd boom mounting pin and bushing | 0.156–0.297 mm | p. 205 |
| Ball joint (2) to solenoid (1) thread clearance | Approx. 1mm | p. 308 |
| Screwing depth b of rod in ball joint | Approx. 12.5 mm | p. 308 |
| Travel speed selector solenoid output pressure (ON) | 3.14 ± 0.49 MPa | p. 322 |
| Swing machinery case mounting bolt | 245 ~ 308.7 Nm | p. 642 |
| Ring gear mounting bolt | 58.5 ~ 73.5 Nm | p. 647 |
