Description

Komatsu PC78UU-6, PC78US-6 2010 Workshop Manual

I’ve lost count of how many hours I’ve burned because some technician didn’t have the factory specs on hand. Maybe you’re stuck on a hydraulic pressure test or chasing a communication error on a PC78US-6. Without the OEM documentation, you’re guessing. This Komatsu PC78UU-6, PC78US-6 2010 Workshop Manual gives you the actual procedures Komatsu wants used. Not a third-party rewrite, not a condensed version – 1025 pages of the real deal.

Komatsu PC78UU-6 and PC78US-6 Workshop Manual: Real Specs for Real Repairs

Every time I see someone try to pull a torque value from a generic online forum, I cringe. This Workshop Manual has the factory numbers for everything from cylinder head bolts to swing circle bearing preload. Section 01 includes the specification drawings, working range, and a complete list of lubricants and coolant. If you need the weight distribution for towing or transport, it’s on page 01-10. No guessing – you get the actual Komatsu data.

01 GENERAL: What the First 20 Pages Cover

You might think the general section is just a formality. Not here. Page 01-1 through 01-22 include the exact dimensions for the PC78UU-6 and PC78US-6, including the offset PPC valve setup unique to the PC78UU-6. There is also a full weight table and the approved coolant mixtures. If you’re servicing a 2010 model, you need to know the correct viscosity for your region; this manual lists it by ambient temperature.

Cooling System and Power Train Details

Section 10 – Structure, Function and Maintenance Standard – dives into the Cooling system, power train, swing machinery, and every hydraulic component from the travel motor to the CLSS control valve. The OEM breakdown includes exploded views and torque sequences that aftermarket manuals never get right. I’ve seen technicians snap bolts on the hydraulic tank bracket because they used a generic torque spec. This manual gives the exact value in foot-pounds for each fastener.

20 Testing and Adjusting – No Shortcuts Here

If you’re diagnosing a hydraulic drift or a travel deviation, section 20 is where you’ll live. It starts with standard value tables for the engine, chassis, and electric parts – then walks through each test in sequence. Need to measure compression pressure on the 4D95LE-2 engine? Procedure is listed. Adjusting the LS valve on a PC78US-6? The manual shows the required tools and the step-by-step adjustments. Even the solenoid valve output pressure test is documented with the exact pressure ranges. You won’t find this level of detail in any third-party reprint.

OEM vs. Aftermarket: Which One Do You Trust?

Aftermarket documentation often takes shortcuts. They might omit the specific connector pin assignments for the controller communication system or skip the troubleshooting flowcharts for the governor control system (E mode). This manual includes all of that. Pages 20-40 through 20-70 cover the troubleshooting sequences for N mode and E mode, the connector arrangement diagrams, and the TVC valve current adjustment table. If you have a controller LED that’s off (trouble E-1), the diagnostic path is laid out. That’s the difference between getting it fixed in one shift and chasing ghosts for two days.

For related documentation, check the Komatsu PC78UU-6 Hydraulic Excavator Operation Manual if you need operating instructions, or the KOMATSU PC78US-6 PC78UU-6 Shop Manual 2003 for older models. For specific pump breakdown, see the Komatsu PC78US-6 Hydraulic Pump Structure and Maintenance. If you need general background on transmissions, external resources like Manual Transmission can help, but for this excavator’s power train, stick with factory data. Another good reference is Manual Transmission.

FAQ

Does this manual cover the engine overhaul for the PC78UU-6?

Yes, section 30 covers disassembly and assembly of the engine and all components.

What about the hydraulic pump adjustment procedures?

Section 20 includes testing and adjusting of hydraulic pressure in work equipment, swing, and travel circuits. It covers measuring LS differential pressure, adjusting the PC valve, testing TVC-EPC solenoid output pressure, and releasing residual pressure. Each procedure lists required tools and factory pressure values. This is the actual Komatsu dealer procedure, not a summary.

If you’re tired of chasing bad data and burning billable hours, stop guessing. Access the Factory Manual for the Komatsu PC78UU-6 and PC78US-6 – it’s the only source you need on your bench.