Description
Komatsu PC78US-6 and PC78UU-6 Excavator Shop Manual — SEBM025109
This Komatsu PC78US-6 PC78UU-6 Shop Manual (document number SEBM025109) is the complete service workshop manual for the Komatsu PC78US-6 and PC78UU-6 hydraulic excavators. It covers serial number PC78US-6 4001 and up, PC78US-6 4809 and up (For Norway), and PC78UU-6 22832 and up. The manual applies to machines equipped with the Komatsu 4D95LE-2 and S4D95LE-3-A diesel engines.
File Details
- Manual Type: Shop Manual (Service Workshop Manual)
- Brand: Komatsu
- Models: PC78US-6, PC78UU-6
- Document Number: SEBM025109
- Engines: 4D95LE-2, S4D95LE-3-A
- Serial Numbers: PC78US-6 4001 and up; PC78US-6 4809 and up (For Norway); PC78UU-6 22832 and up
- Language: English
- Page Count: 785
- File Format: PDF
Chapters Covered
The manual is divided into six major sections:
- 01 General
- Specification dimensions drawing
- Working range drawing
- Specifications
- Weight table
- List of lubricants and coolant
- 10 Structure and Function, Maintenance Standard
- Engine and pump control
- Hydraulic pump (LPD45 + 45)
- Control valve (CLSS system)
- Swing machinery and motor
- Travel motor (GM09VN-E)
- Work equipment cylinders
- Track frame, idler, sprocket, track shoe
- PPC valves (work equipment, travel, blade)
- Solenoid and EPC valves
- Monitor system, sensors, electric control system
- Work equipment dimensions
- 20 Testing and Adjusting
- Standard value tables (engine, chassis, electrical parts)
- Measuring engine speed, exhaust gas color, compression pressure, blow-by pressure
- Adjusting valve clearance, fuel injection timing, engine stop solenoid, fuel control linkage
- Testing and adjusting hydraulic pressure in work equipment, swing, and travel circuits
- Measuring LS differential pressure and adjusting LS valve
- Adjusting PC valve, testing TVC-EPC solenoid output pressure
- Measuring control circuit pressure, PPC valve output pressure
- Testing travel deviation, hydraulic drift, oil leakage
- Releasing residual pressure, bleeding air from hydraulic circuit
- Testing clearance of swing circle bearing
- Testing and adjusting track shoe tension
- Troubleshooting (N, E, C, F, H, M modes)
- Connector types and mounting locations
- Connection table for connector pin numbers
- 30 Disassembly and Assembly
- Removal and installation of counterweight, injection pump, cylinder head, main pump, control pump, engine, hydraulic oil cooler, radiator
- Swing motor and swing machinery assembly
- Center swivel joint assembly
- Control valve assembly
- Work equipment PPC valve, travel PPC valve
- Hydraulic tank, fuel tank, controller, monitor panel
- Air conditioner unit, operator’s cab, floor frame, revolving frame, swing circle
- Work equipment assembly, first boom, second boom, offset bracket
- Track shoe, rubber shoe, final drive, idler, recoil spring, track roller
- Hydraulic cylinder assembly
- 50 Other Specifications (PC78US-6 For Norway)
- Specification dimensions drawing
- Working range drawing
- Specifications and weight table
- Arrangement of hydraulic components
- Boom hydraulic anti-burst valve
- Electric control system and general system diagram
- Overload alarm function and pressure switch
- Meter display unit
- Troubleshooting for controller pump control system and machine monitor system
- 90 Others
- Hydraulic circuit diagrams (blade-less specification, additional attachment circuit, blade specification, Norway specification, PC78UU-6)
- Electrical circuit diagrams (PC78US-6 4001-5500, PC78US-6 5501 and up, PC78US-6 Norway specification, PC78UU-6 22832-23500, PC78UU-6 23501 and up)
This shop manual is the reference Komatsu distributes to service technicians for the PC78US-6 and PC78UU-6. It is divided so that the structure and function of each component is explained first, then testing and adjusting procedures, then disassembly and assembly, and finally the hydraulic and electrical circuit diagrams. The maintenance standard section gives judgement criteria for inspecting disassembled parts, including wear limits, clearances, and service limits.
The testing and adjusting section alone runs to over 500 pages, covering everything from measuring engine compression to diagnosing the CLSS (Closed center Load Sensing System) hydraulic circuit. The troubleshooting section is organized by diagnostic mode (N, E, C, F, H, M) and includes service codes and monitoring codes for the controller and monitor panel.
What This Shop Manual Covers
Engine and Pump Control
The manual covers the 4D95LE-2 and S4D95LE-3-A engines in the context of the machine, including the engine and pump compound control function, TVC-EPC valve adjustment, and the governor control system. Engine specifications, torque values, and service limits are provided in the standard value tables.
Hydraulic System
The hydraulic system section covers the variable-capacity piston pump (LPD45 + 45), the CLSS control valve, LS valve, PC valve, TVC valve, and the pump merge-divider valve. The control valve section includes pressure compensation valves, unload valves, LS bypass plugs, travel junction valves, logic valves, and boom hydraulic drift prevention valves. Complete hydraulic circuit diagrams are provided in Section 90.
Swing and Travel
The swing machinery section covers the reduction gears, swing motor, brake valve, and safety valve. The travel motor section covers the GM09VN-E variable-capacity piston motor, including the 2-stage travel speed changeover mechanism, parking brake, and counterbalance valve. Maintenance standards for backlash, clearances, and wear limits are provided.
Complete PDF Bookmark Tree
Complete Bookmarks
The complete bookmarks in the “Komatsu PC78US-6 PC78UU-6 Excavator Shop Manual – SEBM025109 PDF Download” are as follows:
MAIN MENU
COVERp. 1
CONTENTSp. 2
SAFETYp. 8
FOREWORDp. 10
+01 GENERALp. 27
SPECIFICATION DIMENSIONS DRAWINGp. 28
WORKING RANGE DRAWINGp. 30
SPECIFICATIONSp. 31
WEIGHT TABLEp. 43
LIST OF LUBRICANTS AND COOLANTp. 47
+10 STRUCTURE AND FUNCTION, MAINTENANCE STANDARDp. 48
PTOp. 49
COOLING SYSTEMp. 50
POWER TRAIN SYSTEMp. 51
SWING CIRCLEp. 53
SWING MACHINERYp. 54
TRACK FRAME AND IDLER CUSHIONp. 56
IDLERp. 58
TRACK ROLLERp. 59
CARRIER ROLLERp. 60
SPROCKETp. 61
TRACK SHOEp. 62
ARRANGEMENT OF HYDRAULIC COMPONENTSp. 67
HYDRAULIC TANK AND OIL FILTERp. 69
CENTER SWIVEL JOINTp. 70
TRAVEL MOTORp. 72
WORK EQUIPMENT CYLINDERp. 80
SOLENOID VALVEp. 85
MULTI-CONTROL VALVEp. 93
ACCUMULATOR FOR BRAKEp. 94
+HYDRAULIC PUMP PC78US-6 (with blade) Serial No.: 4001 – 5500; PC78UU-6 (with blade) Serial No.: 22832 – 23500p. 95
PC78US-6 (with blade) Serial No.: 5501 and up; PC78UU-6 (with blade) Serial No.: 23501 and upp. 103
PC78US-6 (without blade) Serial No.: 5501 and upp. 105
CONTROL VALVEp. 117
CLSSp. 141
SWING MOTORp. 179
WORK EQUIPMENT AND SWING PPC VALVEp. 187
TRAVEL PPC VALVEp. 193
OFFSET PPC VALVE, ATTACHMENT PPC VALVE, AND BLADE PPC VALVEp. 197
WORK EQUIPMENTp. 201
DIMENSIONS OF EACH PART OF WORK EQUIPMENTp. 206
AIR CONDITIONER PIPING SYSTEMp. 212
ELECTRIC CONTROL SYSTEMp. 213
SYSTEM COMPONENTSp. 256
MONITOR SYSTEMp. 266
SENSORSp. 272
+20 TESTING AND ADJUSTINGp. 276
+STANDARD VALUE TABLEp. 277
STANDARD VALUE TABLE FOR ENGINEp. 277
STANDARD VALUE TABLE FOR CHASSISp. 279
STANDARD VALUE TABLE FOR ELECTRICAL PARTSp. 288
+TESTING AND ADJUSTINGp. 294
LIST OF DEVICES FOR TESTING, ADJUSTING, AND TROUBLESHOOTINGp. 295
MEASURING ENGINE SPEEDp. 296
MEASURING EXHAUST GAS COLORp. 297
ADJUSTING VALVE CLEARANCEp. 298
MEASURING COMPRESSION PRESSUREp. 299
MEASURING BLOW-BY PRESSUREp. 301
TESTING AND ADJUSTING FUEL INJECTION TIMINGp. 303
MEASURING ENGINE OIL PRESSUREp. 307
ADJUSTING FUEL STOP SOLENOIDp. 308
ADJUSTING FUEL CONTROL LINKAGEp. 310
ADJUSTING ENGINE SPEED SENSORp. 312
TESTING AND ADJUSTING HYDRAULIC PRESSURE IN WORK EQUIPMENT, SWING, AND TRAVEL CIRCUITSp. 313
MEASURING LS DIFFERENTIAL PRESSURE ANDADJUSTING LS VALVEp. 316
ADJUSTING PC VALVEp. 318
TESTING TVC-EPC SOLENOID OUTPUT PRESSUREp. 318
MEASURING CONTROL CIRCUIT PRESSUREp. 319
MEASURING PPC VALVE OUTPUT PRESSUREp. 320
TESTING SOLENOID VALVE OUTPUT PRESSUREp. 321
ADJUSTING WORK EQUIPMENT VALVE AND SWING PPC VALVEp. 323
TESTING TRAVEL DEVIATIONp. 324
TESTING PARTS WHICH CAN CAUSE HYDRAULIC DRIFT OF WORK EQUIPMENTp. 326
MEASURING OIL LEAKAGE FROM SWING AND TRAVEL MOTORSp. 327
RELEASING RESIDUAL PRESSURE FROM HYDRAULIC CIRCUITp. 328
TESTING CLEARENCE OF SWING CIRCLE BEARINGp. 329
TESTING AND ADJUSTING TRACK SHOE TENSIONp. 330
BLEEDING AIR FROM HYDRAULIC CIRCUITp. 331
PROCEDURE FOR ADJUSTING INSTALLATION OF LONG ARMp. 333
REPLACEMENT PROCEDURE OF POTENTIOMETERSp. 334
PROCEDURE FOR TESTING DIODEp. 335
+TROUBLESHOOTINGp. 336
POINTS TO REMEMBER WHEN TROUBLESHOOTINGp. 337
SEQUENCE OF EVENTS IN TROUBLESHOOTINGp. 338
PRECAUTIONS WHEN CARRYING OUT MAINTENANCEp. 339
CHECKS BEFORE TROUBLESHOOTINGp. 347
CONNECTOR TYPES AND MOUNTING LOCATIONS PC78US-6 SERIAL NO. 4001-5500p. 348
CONNECTOR ARRANGEMENT DIAGRAM PC78US-6 SERIAL NO. 4001-5500p. 350
CONNECTOR TYPES AND MOUNTING LOCATIONS PC78US-6 SERIAL NO. 5501 and upp. 353
CONNECTOR ARRANGEMENT DIAGRAM PCUS78-6 SERIAL NO. 5501 and upp. 355
CONNECTOR TYPES AND MOUNTING LOCATIONS PC78UU-6 SERIAL NO. 22832-23500p. 358
CONNECTOR ARRANGEMENT DIAGRAM PC78UU-6 SERIAL NO. 22832-23500p. 361
CONNECTOR TYPES AND MOUNTING LOCATIONS PC78UU-6 SERIAL NO. 23501 and upp. 364
CONNECTOR ARRANGEMENT DIAGRAM PC78UU-6 SERIAL NO. 23501 and upp. 367
CONNECTION TABLE FOR CONNECTOR PIN NUMBERSp. 370
EXPLANATION OF FUNCTIONS OF ELECTRIC SYSTEM CONTROL MECHANISMp. 394
DISPLAY AND SPECIAL FUNCTIONS OF MONITOR PANELp. 398
TVC VALVE CURRENT ADJUSTMENT TABLEp. 411
ADJUSTING SERVICE METERp. 412
HOW TO READ FLOW OF TROUBLESHOOTINGp. 413
CONTENTS AND PROCEDURE OF TROUBLESHOOTINGp. 415
+TROUBLESHOOTING FOR COMMUNICATION SYSTEM (N MODE)p. 416
N-1 DEFECTIVE COMMUNICATIONp. 417
+TROUBLESHOOTING FOR CONTROLLER (GOVERNOR CONTROL SYSTEM) (E MODE)p. 418
PRECAUTIONS FOR TROUBLESHOOTING FOR CONTROLLER (PUMP CONTROL SYSTEM)p. 419
ACTION TAKEN BY CONTROLLER WHEN TROUBLE OCCURS AND PROBLEMS ON MACHINEp. 421
JUDGEMENT TABLE FOR CONTROLLER (GOVERNOR CONTROL SYSTEM) AND ENGINEp. 423
E-1 CONTROLLER POWER SUPPLY IS DEFECTIVE (LED OF CONTROLLER IS TURNED OFF)p. 425
E-2 [E321] (SHORT CIRCUIT IN MOTOR DRIVE RELAY) IS DISPLAYEDp. 426
E-3 [E323] (SHORT CIRCUIT IN ACCELERATOR RELAY) IS DISPLAYEDp. 427
E-4 [E325] (SHORT CIRCUIT IN DECELERATOR RELAY) IS DISPLAYEDp. 429
E-5 [E328] (STALL OF MOTOR) IS DISPLAYEDp. 431
E-6 [E227] (TROUBLE IN ENGINE SPEED SENSOR) IS DISPLAYEDp. 435
E-7 ONE-TOUCH SLOW-DOWN MECHANSISM DOES NOT WORKp. 436
+E-8 ENGINE DOES NOT STARTp. 437
A) [E304] SHORT CIRCUIT IN ENGINE STOP SOLENOID RELAY SYSTEM IS DISPLAYEDp. 437
B) [E314] DISCONNECTION IN ENGINE STOP SOLENOID RELAY SYSTEM IS DISPLAYEDp. 437
C) ENGINE STOP SOLENOID SYSTEMp. 438
D) STARTING SYSTEMp. 441
E-9 ENGINE DOES NOT STOPp. 447
+TROUBLESHOOTING FOR CONTROLLER (PUMP CONTROL SYSTEM) (C MODE)p. 450
PRECAUTIONS FOR TROUBLESHOOTING FOR CONTROLLER (PUMP CONTROL SYSTEM)p. 451
ACTION TAKEN BY CONTROLLER WHEN TROUBLE OCCURS AND PROBLEMS ON MACHINEp. 453
JUDGEMENT TABLE FOR CONTROLLER (PUMP CONTROL SYSTEM) AND HYDRAULIC EQUIPMENTp. 457
ELECTRIC CIRCUIT DIAGRAM OF C MODE SYSTEMp. 459
C-1 [E232] TROUBLE IN TVC-EPC SOLENOID SYSTEMp. 467
C-2 [E233] TROUBLE IN TVC-EPC SOLENOID SYSTEMp. 467
C-3 [E203] TROUBLE IN SWING HOLDING BRAKE SOLENIOD SYSTEMp. 468
C-4 [E213] TROUBLE IN SWING HOLDING BRAKE SOLENIOD SYSTEMp. 468
C-5 [E206] TROUBLE IN 2ND TRAVEL SPEED SELECTION SOLENIOD SYSTEMp. 469
C-6 [E216] TROUBLE IN 2ND TRAVEL SPEED SELECTION SOLENIOD SYSTEMp. 469
C-7 [E403] TROUBLE IN BOOM ANGLE SENSOR CORRECTIONp. 470
C-8 [E406] TROUBLE IN ARM ANGLE SENSOR CORRECTIONp. 470
C-9 [E411] TROUBLE IN OFFSET BOOM ANGLE SENSOR CORRECTIONp. 470
C-10 [E441] TROUBLE IN INTERFERENCE PREVENTION (FRONT) CORRECTIONp. 472
C-11 [E442] TROUBLE IN INTERFERENCE PREVENTION (SIDE) CORRECTION (ONLY PC78UU-6)p. 472
C-12 [E443] TROUBLE IN DEPTH INDICATION CORRECTION (ONLY PC78UU-6)p. 473
C-13 [E258] SHORT CIRCUIT IN 5V SYSTEM OF SENSOR POWER SUPPLY (ONLY PC78UU-6)p. 474
C-14 [E401], C-15 [E402] TROUBLE IN BOOM ANGLE SENSOR SYSTEM (ONLY PC78UU-6)p. 475
C-16 [E404], C-17 [E405] TROUBLE IN ARM ANGLE SENSOR SYSTEM (ONLY PC78UU-6)p. 476
C-18 [E407], C-19 [E408] TROUBLE IN OFFSET ANGLE SENSOR SYSTEM (ONLY PC78UU-6)p. 477
C-20 [E421] DISCONNECTION IN BOOM RAISE EPC SYSTEM IS DISPLAYED (ONLY PC78UU-6)p. 478
C-21 [E422] DISCONNECTION IN BOOM RAISE EPC SYSTEM IS DISPLAYED (ONLY PC78UU-6)p. 479
C-22 [E423] SHORT CIRCUIT OR GROUNDING FAULT IN ARM-IN EPC SYSTEM IS DISPLAYED (ONLY PC78UU-6)p. 480
C-23 [E424] DISCONNECTION IN ARM IN EPC SYSTEM IS DISPLAYED (ONLY PC78UU-6)p. 481
C-24 [E425] SHORT CIRCUIT OR GROUNDING FAULT IN OFFSET LEFT EPC SYSTEM IS DISPLAYED (ONLY PC78UU-6)p. 482
C-25 [E426] DISCONNECTION IN OFFSET LEFT EPC SYSTEM IS DISPLAYED (ONLY PC78UU-6)p. 483
C-26 [E431] SHORT CIRCUIT OR GROUNDING FAULT IN PPC BASIC PRESSURE LOCK SOLENOID SYSTEM IS DISPLAYED (ONLY PC78UU-6)p. 484
C-27 BOOM DOES NOT STOP AUTOMATICALLY AT NORMAL POSITION BUT INTERFERES WHEN IT IS RAISED (ONLY PC78UU-6)p. 487
C-28 ARM DOES NOT STOP AUTOMATICALLY AT NORMAL POSITION BUT INTERFERES WHEN IT IS MOVED IN (ONLY PC78UU-6)p. 488
C-29 OFFSET DOES NOT STOP AUTOMATICALLY AT NORMAL POSITION BUT INTERFERES WHEN IT IS MOVED TO LEFT (ONLY PC78UU-6)p. 489
C-30 WORK EQUIPMENT STOPS FAR OR NEAR (ONLY PC78UU-6)p. 490
C-31 BUZZER SOUNDS FOR 7 SECONDS WHILE EMERGENCY WORK EQUIPMENT OPERATION SWITCH IS NOT TURNED ON (ONLY PC78UU-6)p. 491
C-32 BOOM RAISE END CUSHION DOES NOT WORK AT ALL OR NORMALLY (ONLY PC78UU-6)p. 493
C-33 ARM-IN END CUSHION DOES NOT WORK AT ALL OR NORMALLY (ONLY PC78UU-6)p. 494
C-34 OFFSET SEND CUSHION DOES NOT WORK AT ALL OR NORMALLY (ONLY PC78UU-6)p. 495
C-35 WORK EQUIPMENT STOPS AFTER OR BEFORE SET HEIGHT (ONLY PC78UU-6)p. 496
C-36 WHEN DEPTH DISPLAY IS RESET, 0.0 M IS NOT INDICATED AT GL (ONLY PC78UU-6)p. 497
C-37 WORK EQUIPMENT STILL MOVES AFTER WORK EQUIPMENT LOCK LEVER IS SET TO LOCKp. 498
C-38 MACHINE DOES NOT SWINGp. 501
C-39 TRAVEL SPEED DOES NOT RISEp. 502
C-40 TROUBLE IN CONTROLLER POWER SUPPLY (LED OF CONTROLLER IS TURNED OFF)p. 502
+TROUBLESHOOTING FOR CONTROLLER (INPUT SIGNAL SYSTEM) (F MODE)p. 503
F-1 BIT PATTERN 1023-4 SWING PRESSURE SWITCH DOES NOT LIGHT UPp. 504
F-2 BIT PATTERN 1023-3 TRAVEL PRESSURE SWITCH DOES NOT LIGHT UPp. 505
F-3 BIT PATTERN 1023-6 BOOM RAISE PRESSURE SWITCH DOES NOT LIGHT UPp. 506
F-4 BIT PATTERN 1023-5 ARM IN PRESSURE SWITCH DOES NOT LIGHT UPp. 507
F-5 BIT PATTERN 1026-1 DECELERATION SWITCH OF LEFT KNOB DOES NOT LIGHT UPp. 508
F-6 BIT PATTERN 1021-4 2ND TRAVEL SPEED SELECTION SWITCH (PEDAL) DOES NOT LIGHT UP (US WITH BLADE)p. 509
F-7 BIT PATTERN 1021-3 COMPRESSOR SIGNAL DOES NOT LIGHT UPp. 510
F-8 BIT PATTERN 1026-(3) EMERGENCY WORK EQUIPMENT OPERATION SWITCH DOES NOT LIGHT UP (ONLY PC78UU-6)p. 511
+TROUBLESHOOTING FOR HYDRAULIC AND MECHANICAL SYSTEMS (H MODE)p. 512
TABLE OF HYRAULIC FAILURE MODES AND CAUSESp. 515
+H-1 SPEED OR POWER OF 2 OR MORE SYSTEMS OF WORK EQUIPMENT (BOOM, ARM, BUCKET, OFFSET), TRAVEL, SWING, AND BLADE IS LOWp. 517
A) SPEED OR POWER OF ALL WORK EQUIPMENT (INCLUDING BLADE), TRAVEL AND SWING IS LOWp. 517
B) SPEED OR POWER OF ALL WORK EQUIPMENT (EXCLUDING BLADE), AND TRAVEL IS LOWp. 518
C) SPEED OR POWER OF SWING AND BLADE IS LOWp. 518
D) SPEED OR POWER OF TRAVEL AND BLADE IS LOWp. 519
E) SPEED OR POWER OF ALL WORK EQUIPMENT (EXCLUDING BLADE) IS LOWp. 519
F) SPEED OR POWER OF TRAVEL AND SWING IS LOWp. 520
G) SPEED OR POWER OF ALL WORK EQUIPMENT AND SWING IS LOWp. 520
H-2 ENGINE SPEED LOWERS EXTREMELY OR ENGINE STALLSp. 521
+H-3 2 OR MORE SYSTEMS (INCLUDING BLADE), TRAVEL, AND SWING SYSTEMS DO NOT MOVEp. 523
A) ALL WORK EQUIPMENT (INCLUDING BLADE), TRAVEL, AND SWING SYSTEMS DO NOT MOVEp. 523
B) ALL WORK (EXCLUDING BLADE) AND TRAVEL SYSTEMS DO MOVEp. 524
C) SWING AND BLADE SYSTEMS DO NOT MOVEp. 524
D) TRAVEL AND BLADE SYSTEMS DO NOT MOVEp. 525
E) ALL WORK EQUIPMENT (EXCLUDING BLADE) DOES NOT MOVEp. 525
H-4 ABNORMAL SOUND COMES OUT (FROM AROUND PUMP)p. 526
H-5 FINE CONTROLLABILITY OR RESPONSE IS LOWp. 527
H-6 HYDRAULIC DRIFT IS LARGE (ALL WORK EQUIPMENT AND BLADE)p. 528
+H-7 BOOM SPEED OR POWER IS LOW (OTHER WORK EQUIPMENT IS NORMAL)p. 529
A) BOOM RAISE SPEED OR POWER IS LOWp. 529
B) BOOM LOWER SPEED OR POWER IS LOWp. 530
+H-8 ARM SPEED OR POWER IS LOW (OTHER WORK EQUIPMENT IS NORMAL)p. 531
A) ARM IN SPEED OR POWER IS LOWp. 531
B) ARM OUT SPEED OR POWER IS LOWp. 533
+H-9 BUCKET SPEED OR POWER IS LOW (OTHER WORK EQUIPMENT IS NORMAL)p. 534
A) BUCKET CURL SPEED OR POWER IS LOWp. 534
B) BUCKET DUMP SPEED OR POWER IS LOWp. 535
+H-10 OFFSET SPEED OR POWER IS LOW (OTHER WORK EQUIPMENT IS NORMAL) (ONLY PC78UU-6)p. 536
A) OFFSET LEFT SPEED OR POWER IS LOWp. 536
B) OFFSET RIGHT SPEED OR POWER IS LOWp. 537
+H-11 BOOM DOES NOT MOVEp. 538
A) BOOM DOES NOT RISEp. 538
B) BOOM DOES NOT LOWERp. 539
+H-12 ARM DOES NOT MOVEp. 540
A) ARM DOES NOT MOVE INp. 540
B) ARM DOES NOT MOVE OUTp. 541
+H-13 BUCKET DOES NOT MOVEp. 542
A) BUCKET DOES NOT CURLp. 542
B) BUCKET DOES NOT DUMPp. 543
+H-14 OFFSET BOOM DOES NOT MOVE (ONLY PC78UU-6)p. 544
A) OFFSET BOOM LEFT DOES NOT MOVEp. 544
B) OFFSET BOOM RIGHT DOES NOT MOVEp. 545
H-15 HYDRAULIC DRIFT OF BOOM IS LARGEp. 546
H-16 HYDRAULIC DRIFT OF ARM IS LARGEp. 546
H-17 HYDRAULIC DRIFT OF BUCKET IS LARGEp. 547
+H-18 HYDRAULIC DRIFT OF OFFSET IS LARGE (ONLY PC78UU-6)p. 547
A) HYDRAULIC DRIFT OF OFFSET TO LEFT IS LARGEp. 547
B) HYDRAULIC DRIFT OF OFFSET TO RIGHT IS LARGEp. 547
H-19 TIME LAG IS LARGE (WHEN ENGINE SPEED IS LOW)p. 548
H-20 PART LOADED MORE MOVES SLOWER IN COMPOUND OPERATION OF WORK EQUIPMENTp. 548
H-21 BOOM RAISE SPEED IS LOW IN COMPOUND OPERATION OF SWING AND BOOM RAISEp. 549
H-22 TRAVEL SPEED LOWERS EXTREMELY IN COMPOUND OPERATION OF TRAVEL AND BOOM RAISEp. 549
H-23 SPEED IS LOW IN COMPOUND OPERATION OF WORK EQUIPMENT RELIEF AND SWING, WORK EQUIPMENT RELIEF AND OTHER WORK EQUIPMENTp. 549
H-24 WORK EQUIPMENT DOES NOT MOVE OR ITS SPEED IS LOW IN COMPOUND OPERAITON OF TRAVEL AND WORK EQUIPMENTp. 550
+H-25 TRAVEL DEVIATION IS LARGEp. 551
A) TRAVEL DEVIATION DEVIATION IS LARGE DURING ORDINARY TRAVELp. 551
B) TRAVEL DEVIATION IS LARGE WHEN MACHINE STARTS (BUT DURING NORMAL ORDINARY TRAVEL)p. 552
H-26 TRAVEL DEVIATION IS LARGE IN COMPOUND OPERATION OF TRAVEL AND SWING, TRAVEL AND WORK EQUIPMENTp. 553
H-27 TRAVEL SPEED OR POWER IS LOW (WORK EQUIPMENT, SWING AND BLADE OPERATIONS ARE NORMAL)p. 554
H-28 MACHINE CANNOT BE STEERED SHARPLY OR STEERING FORCE IS INSUFFICIENTp. 556
H-29 TRAVEL SPEED DOES NOT CHANGE AT ALL OR DOES NOT CHANGE QUICKLYp. 557
H-30 MACHINE DOES NOT TRAVELp. 558
H-30 SUPPLEMENTp. 559
H-31 OVERRUN OF TRAVEL IS LARGEp. 560
H-32 TRAVEL HYDRAULIC DRIFT IS LARGEp. 560
H-33 FINE CONTROLLABILITY OR RESPONSE IS LOWp. 561
H-34 SWING SPEED OR POWER IS LOW (WORK EQUIPMENT, SWING, AND BLADE OPERATIONS ARE NORMAL)p. 562
+H-35 MACHINE DOES NOT SWING (WORK EQUIPMENT, TRAVEL, AND BLADE OPERATIONS ARE NORMAL)p. 565
A) SWING SPEED OR POWER IS LOW IN BOTH DIRECTIONSp. 565
B) SWING SPEED OR POWER IS LOW IN EITHER DIRECTIONp. 566
+H-36 SWING ACCLERATION IS LOWp. 567
A) SWING ACCELERATION IS LOW IN BOTH DIRECTIONSp. 567
B) SWING ACCELERATION IS LOW IN EITHER DIRECTIONp. 567
+H-37 OVERRUN OF SWING IS LARGEp. 568
A) OVERRUN OF SWING IS LARGE IN BOTH DIRECTIONSp. 568
B) OVERRUN OF SWING IS LARGE IN EITHER DIRECTIONp. 568
H-38 LARGE SHOCK IS MADE WHEN MACHINE STOPS SWINGINGp. 569
H-39 LARGE ABNORMAL SOUND IS MADE WHEN MACHINE STOPS SWINGINGp. 569
H-40 SWING HYDRAULIC DRIFT IS LARGEp. 570
H-41 FINE CONTROLLABILTY MORE RESPONSE OF SWING IS LOWp. 571
H-42 BLADE SPEED OR POWER IS LOW (WORK EQUIPMENT, TRAVEL, AND BLADE OPERATIONS ARE NORMAL)p. 572
+H-43 BLADE DOES NOT MOVE (WORK EQUIPMENT, TRAVEL, AND SWING OPERATIONS ARE NORMAL)p. 573
A) BLADE DOES NOT RISEp. 573
B) BLADE DOES NOT LOWERp. 574
H-44 HYDRAULIC DRIFT OF BLADE IS LARGEp. 575
H-45 FINE CONTROLLABILITY OR REPSONSE OF BLADE IS LOWp. 576
H-46 MONITOR PANEL DISPLAYS ERROR CODE AND BOOM RAISE, ARM IN, AND OFFSET LEFT OPERATIONS STOP JUST BEFORE INTERFERENCE (ONLYp. 577
H-47 MACHINE DOES NOT STOP BOOM RAISE, ARM IN, AND OFFSET LEFT OPERATIONS AUTOMATICALLY BUT INTERFERES (ONLY PC78UU-6)p. 577
+TROUBLESHOOTING FOR MACHINE MONITOR SYSTEM (M MODE)p. 578
ACTION TAKEN BY CONTROLLER WHEN TROUBLE OCCURS AND PROBLEMS ON MACHINEp. 579
ELECTRIC CIRCUIT DIAGRAM OF M MODE SYSTEMp. 581
M-1 [E101] (ERROR HISTORY DATA ARE ABNORMAL) IS DISPLAYEDp. 585
M-2 [E108] (ENGINE COOLANT TEMPERATURE IS 105°C ) IS DISPLAYEDp. 586
M-3 [E114] (WIPER FORWARD OUTPUT IS SHORTED) IS DISPLAYEDp. 586
M-4 [E115] (WIPER REVERSE OUTPUT OF 24 V) IS DISPLAYEDp. 586
M-5 [E116] (CONTACT WITH WASHER OUTPUT OF 24 V) IS DISPLAYEDp. 586
M-6 [E117] (WIPER DOES NOT START WIPING IN 10 SECONDS) IS DISPLAYEDp. 586
M-7 [E118] (WIPER IS NOT RETRACTED IN 10 SECONDS) IS DISPLAYEDp. 586
+M-8 WHEN STARTING SWITCH IS TURNED ON POSITION, MONITOR PANEL SEGMENTS DO NOT LIGHT UP FOR 3 SECONDSp. 587
A) MONITOR PANEL SEGMENTS DO NOT LIGHT UP AT ALLp. 587
B) SOME MONITOR PANEL SEGMENTS DO NOT LIGHHT UP AT ALLp. 587
M-9 WHEN STARTING SWITCH IS TURNED TO ON POSITION, MONITOR PANEL SEGMENTS LIGHT UP BUT DO NOT GO OFFp. 588
M-10 WHILE PREHEATING IS NOT EXECUTED, "PREHEATER MONITOR" LIGHTS UPp. 588
+M-11 WHEN STARTING SWITCH IS SET TO ON POSITION AND ENGINE IS STARTED, BASIC CHECK ITEMS FLASHp. 589
A) ALTERNATOR SYSTEMp. 589
B) ENGINE OIL SYSTEMp. 590
+M-12 WHEN STARTING SWITCH IS SET TO ON POSITION (BUT ENGINE IS STOPPED), CAUTION ITEMS AND EMERGENCY STOP ITEMS (EXCLUDING BAp. 591
A) ALTERNATOR SYSTEMp. 591
B) ENGINE OIL SYSTEMp. 592
+M-13 WHEN STARTING SWITCH IS SET TO ON POSITION AND ENGINE IS STARTED, CAUTION ITEMS AND EMERGENCY STOP ITEMS FLASH (WHEN THEp. 593
A) "ENGINE OIL" FLASHESp. 593
B) "CHARGE LEVEL" FLASHESp. 593
C) "COOLANT TEMPERATURE" FLASHESp. 594
D) "FUEL LEVEL" FLASHESp. 595
M-14 WHEN STARTING SWITCH IS SET TO ON POSITION (BUT ENGINE IS STOPPED), BUZZER DOES NOT SOUND FOR 1 SECONDp. 596
M-15 MONITOR PLANE LAMP FOR NIGHTTIME IS NOT TURNED ON (LC DISPLAY IS NORMAL)p. 597
M-16 COOLANT TEMPERATURE GAUGE DOES NOT RISEp. 598
M-17 COOLANT TEMPERATURE GAUGE IS NOT DISPLAYED (GAUGE DOES NOT RISE TO 1ST LINE DURING OPERATION)p. 598
M-18 FUEL LEVEL GAUGE ALWAYS DISPALYS FULLp. 599
M-19 FUEL LEVEL GAUGE IS NOT DISPLAYEDp. 599
M-20 WHILE ENGINE IS RUNNING, SERVICE METER DOES NOT ADVANCEp. 600
M-21 TROUBLE IN FUEL LEVEL SENSORp. 601
M-22 TROUBLE IN COOLANT TEMPERATURE SENSORp. 602
+M-23 WIPER DOES NOT OPERATE OR OPERATES WHILE WIPER SWITCH IS TURNED OFFp. 603
A) WIPER DOES NOT OPERATEp. 603
B) WIPER OPERATES WHILE WIPER SWITCH IS TURNED OFFp. 603
+M-24 WASHER MOTOR DOES NOT OPERATE OR OPERATES WHILE WASHER SWITCH IS TURNED OFFp. 606
A) WASHER MOTOR DOES NOT OPERATEp. 606
B) WASHER OPERATES WHILE WIPER SWITCH IS TURNED OFFp. 606
M-25 DEPTH SET 0 MODE AND HEIGHT MODE CANNOT BE SELECTED AND SET (ONLY PC78UU-6)p. 608
+30 DISASSEMBLY AND ASSEMBLYp. 609
METHOD OF USING MANUALp. 610
PRECAUTIONS WHEN CARRYING OUT OPERATIONp. 611
SPECIAL TOOL LISTp. 615
REMOVAL, INSTALLATION OF COUNTERWEIGHT ASSEMBLYp. 621
REMOVAL, INSTALLATION OF INJECTION PUMP ASSEMBLYp. 622
REMOVAL, INSTALLATION OF CYLINDER HEAD ASSEMBLYp. 625
REMOVAL, INSTALLATION OF MAIN PUMP ASSEMBLYp. 633
REMOVAL, INSTALLATION OF CONTROL PUMP ASSEMBLYp. 636
REMOVAL, INSTALLATION OF ENGINE AND MAIN PUMP ASSEMBLYp. 637
REMOVAL, INSTALLATION OF HYDRAULIC OIL COOLER ASSEMBLYp. 640
REMOVAL, INSTALLATION OF RADIATOR ASSEMBLYp. 640
REMOVAL, INSTALLATION OF SWING MOTOR AND SWING MACHINERY ASSEMBLYp. 642
DISASSEMBLY, ASSEMBLY OF SWING MACHINERY ASSEMBLYp. 643
REMOVAL, INSTALLATION OF SWING MOTOR ASSEMBLYp. 649
REMOVAL, INSTALLATION OF CENTER SWIVEL JOINT ASSEMBLYp. 649
DISASSEMBLY, ASSEMBLY OF CENTER SWIVEL JOINT ASSEMBLYp. 651
REMOVAL, INSTALLATION OF CONTROL VALVE ASSEMBLYp. 652
ASSEMBLY OF CONTROL VALVE ASSEMBLYp. 653
ASSEMBLY OF WORK EQUIPMENT PPC VALVE ASSEMBLYp. 654
ASSEMBLY OF TRAVEL PPC VALVE ASSEMBLYp. 655
REMOVAL, INSTALLATION OF HYDRAULIC TANK ASSEMBLYp. 657
REMOVAL, INSTALLATION OF FUEL TANK ASSEMBLYp. 658
REMOVAL, INSTALLATION OF CONTROLLER ASSEMBLYp. 659
REMOVAL, INSTALLATION OF MONITOR PANEL ASSEMBLYp. 660
REMOVAL, INSTALLATION OF AIR CONDITIONER UNIT ASSEMBLYp. 660
REMOVAL, INSTALLATION OF OPERATOR'S CAB ASSEMBLYp. 662
REMOVAL, INSTALLATION OF FLOOR FRAME ASSEMBLYp. 663
REMOVAL, INSTALLATION OF REVOLVING FRAME ASSEMBLYp. 665
REMOVAL, INSTALLATION OF SWING CIRCLE ASSEMBLYp. 666
REMOVAL, INSTALLATION OF WORK EQUIPMENT ASSEMBLYp. 667
REMOVAL, INSTALLATION OF FIRST BOOM ASSEMBLYp. 671
REMOVAL, INSTALLATION OF SECOND BOOM ASSEMBLYp. 674
REMOVAL, INSTALLATION OF OFFSET BRACKET ASSEMBLYp. 675
EXPANSION, INSTALLATION OF STEEL SHOE, RUBBER PAD SHOE, ROAD LINER ASSEMBLYp. 677
REMOVAL, INSTALLATION OF RUBBER SHOE ASSEMBLYp. 678
REMOVAL, INSTALLATION OF FINAL DRIVE ASSEMBLYp. 678
ASSEMBLY OF IDLER ASSEMBLYp. 679
DISASSEMBLY, ASSEMBLY OF RECOIL SPRING ASSEMBLYp. 681
DISASSEMBLY, ASSEMBLY OF TRACK ROLLER ASSEMBLYp. 683
DISASSEMBLY, ASSEMBLY OF HYDRAULIC CYLINDER ASSEMBLYp. 686
+50 OTHER SPECIFICATIONSp. 690
PC78US-6 (FOR NORWAY)p. 692
CONTENTSp. 693
+GENERALp. 694
SPECIFICATION DIMENSIONS DRAWING (FOR NORWAY)p. 694
WORKING RANGE DRAWING (FOR NORWAY)p. 695
SPECIFICATIONS (FOR NORWAY)p. 696
WEIGHT TABLE (FOR NORWAY)p. 702
+STRUCTURE, FUNCTION, AND MAINTENANCE STANDARDp. 705
ARRANGEMENT OF HYDRAULIC COMPONENTS (FOR NORWAY)p. 705
DIMENSIONS OF EACH PART OF WORK EQUIPMENTp. 706
BOOM HYDRAULIC ANTI-BURST VALVEp. 708
ELECTRIC CONTROL SYSTEM (FOR NORWAY)p. 713
GENERAL SYSTEM DIAGRAM (FOR NORWAY)p. 714
OVERLOAD ALARM FUNCTION (FOR NORWAY)p. 718
OVERLOAD ALARM PRESSURE SWITCH (FOR NORWAY)p. 719
METER DISPLAY UNIT (FOR NORWAY)p. 720
+TROUBLESHOOTINGp. 721
CONNECTION TYPES AND MOUNTING LOCATIONSp. 724
EXPLANATION OF FUNCTIONS OF ELECTRIC SYSTEM CONTROL MECHANISMp. 733
DISPLAY AND SPECIAL FUNCTIONS OF MONITOR PANELp. 734
+TROUBLESHOOTING FOR CONTROLLER PUMP CONTROL SYSTEM (C MODE)p. 742
PRECAUTIONS FOR TROUBLESHOOTING CONTROLLER (PUMP CONTROL SYSTEM)p. 743
ACTION TAKEN BY CONTROLLER WHEN TROUBLE OCCURS AND PROBLEMS ON MACHINEp. 745
JUDGEMENT TABLE FOR CONTROLLER (PUMP CONTROL SYSTEM) AND HYDRAULIC EQUIPMENTp. 747
ELECTRIC CIRCUIT DIAGRAM OF C MODE SYSTEMp. 749
C-1 [E232] TROUBLE IN TVC-EPC SOLENOID SYSTEMp. 751
C-2 [E233] TROUBLE IN TVC-EPC SOLENOID SYSTEMp. 751
C-3 [E203] TROUBLE IN SWING HOLDING BRAKE SOLENOID SYSTEMp. 752
C-4 [E213] TROUBLE IN SWING HOLDING BRAKE SOLNOID SYSTEMp. 752
C-5 [E206] TROUBLE IN 2ND TRAVEL SPEED SELECTION SOLENOID SYSTEMp. 753
C-6 [E216] TROUBLE IN 2ND TRAVEL SPEED SELECTION SOLENOID SYSTEMp. 753
C-7 [E251] TROUBLE IN BOOM PRESSURE SENSOR (OVERLOAD SENSOR) SYSTEMp. 754
C-8 [E258] SHORT CIRCUIT IN 5 V SYSTEM OF SENSOR POWER SUPPLYp. 754
C-9 WORK EQUIPMENT STILL MOVES AFTER WORK EQUIPMENT LOCK LEVER IS SET TO LOCKp. 755
C-10 MACHINE DOES NOT SWINGp. 757
C-11 TRAVEL SPEED DOES NOT RISEp. 758
+TROUBLESHOOTING FOR MACHINE MONITOR SYSTEM (M MODE)p. 759
ACTION TAKEN BY CONTROLLER WHEN TROUBLE OCCURS AND PROBLESM ON MACHINEp. 579
ELECTRIC CIRCUIT DIAGRAMp. 760
M-1 [E101] (ERROR HISTORY DATA ARE ABNORMAL) IS DISPLAYEDp. 585
M-2 [E108] (ENGINE COOLANT TEMPERATURE IS 105°C) IS DISPLAYEDp. 586
M-3 [E114] (WIPER FORWARD OUTPOUT IS HSORTED) IS DISPLAYEDp. 586
M-4 [E115] (WIPER REVERSE OUTPUT IS SHORTED) IS DISPLAYEDp. 586
M-5 [E-116] (CONTACT WITH WASHER OUTPUT OF 24 V) IS DISPLAYEDp. 586
M-6 [E117] (WIPER DOES NOT START WIPING IN 10 SECONDS) IS DISPLAYEDp. 586
M-7 [E118] (WIPER IS NOT RETRACTED IN 10 SECONDS) IS DISPLAYEDp. 586
+M-8 WHEN STARTING SWITCH IS TURNED TO ON POSITION, MONITOR PANEL SEGMENTS DO NOT LIGHT UP FOR 3 SECONDSp. 587
A) MONITOR PANEL SEGEMENTS DO NOT LIGHT UP AT ALLp. 587
B) SOME MONITOR PANEL SEGMENTS DO NOT LIGHT UPp. 587
M-9 WHEN STARTING SWITHC IS SET TO ON POSITION, ALL MONITOR PANEL SEGMENTS LIGHT UP BUT DO NOT GO OFFp. 588
M-10 WHILE PREHEATING IS EXECUTED, "PREHEATER MONITOR" LIGHT UPp. 588
+M-11 WHEN STARTING SWITCH IS SET TO ON POSITION AND ENGINE IS STARTED, BASIC CHECK ITEMS FLASHp. 764
A) ALTERNATOR SYSTEMp. 764
B) ENGINE OIL PRESSURE SYSTEMp. 765
+M-12 WHEN STARTING SWITCH IS SET TO ON POSITION (BUT ENGINE IS STOPPED),CAUTION ITEMS AND EMERGENCY STOP ITEMS (EXCLUDING BATTERY AND ENGINE OIL) FLASHp. 766
A) ALTERNATOR SYSTEMp. 766
B) ENGINE OIL PRESSURE SENSOR SYSTEMp. 767
+M-13 WHEN STARTING SWITCH IS SET TO ON POSITION AND ENGINE IS STARTED, CAUTION ITEMS AND EMERGENCY STOP ITEMS FLASH (WHEN THERE IS NOT ABNORMALITY IN ISPECTION ITEMS AND ENGINE BEFORE TROUBLESHOOTING)p. 593
A) "ENGINE OIL" FLASHESp. 593
B) "CHARGE LEVEL" FLASHESp. 593
C) "FUEL LEVEL" FLASHESp. 594
D) "FUEL LEVEL" FLASHESp. 595
M-14 WHEN STARTING SWITCH IS SET TO ON POSITION (BUT ENGIN EIS STOPPED), BUZZER DOES NOT SOUND FOR 1 SECOND WHILE CATION ITEM IS FLASHING, BUZZER DOES NOT SOUNDp. 596
M-15 MONITOR PANEL LAMP FOR NIGHTTIME IS NOT TURNED ON (LC DISPLAYED IS NORMAL)p. 597
M-16 COOLANT TEMPERATURE GAUGE DOES NOT RISEp. 598
M-17 COOLANT TEMPERATURE GAUGE IS NOT DISPLAYED (GAUGE DOES NOT RISE TO 1ST LINE DURING OPERATION)p. 598
M-18 FUEL LEVEL GAUGE ALWAYS DISPLAYS FULLp. 599
M-19 FUEL LEVEL GAUGE IS NOT DISPLAYEDp. 599
M-20 WHILE ENGINE IS RUNNING, SERVICE METER DOES NOT ADVANCEp. 600
M-21 TROUBLE IN FUEL LEVEL SENSORp. 601
M-22 TROUBLE IN COOLANT TEMPERATURE SENSORp. 602
+M-23 WIPER DOES NOT OPERATOR OR OPERATES WHILE WIPER SWITCH IS TURNED OFFp. 603
A) WIPER DOES NOT OPERATEp. 603
B) WIPER OPERATES WHILE WIPER SWICH IS TURNED OFFp. 603
+M-24 WASHER MOTOR DOES NOT OPERATE OR OPERATES WHILE WASHER SWITCH IS TURNED OFFp. 606
A) WASHER MOTOR DOES NOT OPERATEp. 606
B) WASHER OPERATES WHILE WIPER SWITCH IS TURNED OFFp. 606
+90 OTHERSp. 768
+HYDRAULIC CIRCUIT DIAGRAMp. 769
PC78US-6 BLADE-LESS SPECIFICATIONp. 769
PC78US-6 ADDITIONAL ATTACHMENT CIRCUITp. 770
PC78US-6 BLADE SPECIFICATIONp. 771
PC78US-6 NORWAY SPECIFICATIONp. 772
PC78UU-6p. 773
+ELECTRICAL CIRCUIT DIAGRAMp. 774
PC78US-6 SERIAL NO.: 4001-5500 (1/2)p. 774
PC78US-6 SERIAL NO.: 4001-5500 (2/2)p. 775
PC78US-6 SERIAL NO.: 5501 and up (1/2)p. 776
PC78US-6 SERIAL NO.: 5501 and up (2/2)p. 777
PC78US-6 SERIAL NO.: 4809-5500 NORWAY SPECIFICATION (1/2)p. 778
PC78US-6 SERIAL NO.: 4809-5500 NORWAY SPECIFICATION (2/2)p. 779
PC78US-6 SERIAL NO.: 5501 and up NORWAY SPECIFICATION (1/2)p. 780
PC78US-6 SERIAL NO.: 5501 and up NORWAY SPECIFICATION (2/2)p. 781
PC79UU-6 SERIAL NO.: 22832-23500 (1/2)p. 782
PC79UU-6 SERIAL NO.: 22832-23500 (2/2)p. 783
PC79UU-6 SERIAL NO.: 23501 and up (1/2)p. 784
PC79UU-6 SERIAL NO.: 23501 and up (2/2)p. 785
Work Equipment
Boom, arm, bucket, offset (PC78UU-6), and blade cylinders are covered with dimensional drawings, clearance specifications, tightening torques, and disassembly/assembly procedures. The work equipment section also covers the PPC valves, EPC valves, and the interference prevention system for the PC78UU-6.
Undercarriage
Track frame, idler cushion, recoil spring, track roller, carrier roller, sprocket, and track shoe (city pad shoe, road liner, triple shoe, rubber shoe) are covered with wear limits and maintenance standards. Track shoe tension adjustment and final drive removal/installation are included.
Electrical System
The electric control system section covers the controller, monitor panel, sensors, PPC oil pressure switches, potentiometers, and solenoid valves. Electrical circuit diagrams are provided for each model and serial number range. The self-diagnostic function, user codes, service codes, and monitoring codes are explained in detail.
Troubleshooting
The troubleshooting section is organized by system: communication system (N mode), governor control system (E mode), pump control system (C mode), input signal system (F mode), hydraulic and mechanical systems (H mode), and machine monitor system (M mode). Each failure mode has a diagnostic flow with causes and remedies.
Why This Manual Matters
When servicing a Komatsu PC78US-6 or PC78UU-6, using the correct specifications and procedures is critical. The hydraulic system operates at pressures up to 26.5 MPa (270 kg/cm²), and the CLSS system requires precise adjustment of the LS valve and PC valve to maintain proper pump control. Incorrect adjustment can lead to poor performance, overheating, or component damage.
This shop manual provides the actual Komatsu service procedures, torque values, wear limits, and diagnostic flowcharts that Komatsu technicians use. Whether you are rebuilding a hydraulic cylinder, adjusting the LS differential pressure, diagnosing a controller fault code, or replacing a final drive, the manual gives you the sequence, the specifications, and the judgement criteria.
Who This Manual Is For
This manual is for mechanics, technicians, and owner-operators who service and repair the Komatsu PC78US-6 and PC78UU-6. It assumes familiarity with basic mechanical and hydraulic principles. The testing and adjusting section references special tools (with Komatsu part numbers) that are listed in the special tool list.
Instant PDF Delivery
This Komatsu PC78US-6 PC78UU-6 shop manual is delivered as a PDF download immediately after payment. There is no shipping, no waiting for a physical book, and no risk of a lost or damaged package. The PDF can be viewed on any device — computer, tablet, or smartphone — and you can print the pages you need for the workshop. Whether you need the full 785-page manual for a complete overhaul or just the hydraulic circuit diagram for a specific repair, the file is yours to keep and reference as often as you need.
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