Your next pre-start walkaround goes by the book with this 289-page Komatsu PC78US-6 Operation and Maintenance Manual PDF (OEM ID SEAM044602T) open beside the hydraulic excavator, from fluid levels to greasing bucket pins. Roughly a quarter of the book is maintenance: a schedule chart running from the initial 250-hour check out to the 5000-hour service, a wear parts list, lubricant and coolant tables, and a tightening torque list. Ahead of that sit the monitor panel and switch layout, starting and travel procedures, slope and mud recovery, trailer loading and lifting, cold-weather operation, and an attachment section covering hydraulic breaker use and control pattern changes. Refill with 7 liters of engine oil when you change the oil and fuel filters at 500 hours, and hold 9/16-18UNF hydraulic hose fittings to 35 to 63 N·m. An oil change stalls fast over one missing refill figure. Bookmarks and a searchable text layer take you to the right interval or warning light in two clicks.
What's Inside This Komatsu PC78US-6 Operator Manual
| System | Pages | Key Topics |
|---|---|---|
| Safety | 16-53 | Safety Information, Safety Labels (Location of Safety Labels) |
| Machine View Illustrations and Controls | 54-71 | Machine View Illustrations, Monitoring System, Switches, Control Levers and Pedals |
| Machine Operations and Controls | 72-108 | Starting Engine, Stopping Engine, Machine Operation, Traveling, Swinging, Work Equipment Controls |
| General Operation Information | 109-148 | Prohibited Operations, Traveling on Slopes, Escape From Mud, Recommended Applications, Bucket Replacement |
| Transportation and Cold Weather Operation | 149-171 | Transportation Procedure, Loading and Unloading, Lifting Machine, Cold Weather Operation |
| Troubles and Actions | 172-185 | Running Out of Fuel, Towing, Discharged Battery, Electronic Control System, Machine Monitoring System |
| Maintenance | 186-259 | Maintenance Information, Lubricants, Coolant and Filters (Handling Oil, Fuel, Coolant, And Performing Oil Clinic, Electric System Maintenance), Wear Parts (List) |
| Specifications | 260-263 | Operating Weight, Bucket Capacity, Engine Horsepower, Overall Length, Overall Height, Track Width |
| Attachments and Options | 264-285 | Attachments and Options - General Inforamtion (Safety First, Attachment Installation, Bucket with Hook) |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Fuel filter replacement frequency | EVERY 500 HOURS SERVICE | p. 192 |
| Engine oil filter replacement frequency | EVERY 500 HOURS SERVICE | p. 192 |
| Engine oil refill capacity | 7 liters | p. 245 |
| Hydraulic hose tightening torque (9/16-18UNF) | 35 - 63 N·m | p. 197 |
| Hydraulic hose tightening torque (11/16-16UN) | 54 - 93 N·m | p. 197 |
| Hydraulic Hose Tightening Torque (1-14UNS) | 128-186 N·m | p. 197 |
| Standard deflection (steel shoes) | 10 to 30 mm (0.4 to 1.2 in) | p. 211 |
| Standard deflection (rubber shoes) | 1 to 3 mm (0.039 to 0.118 in) | p. 215 |
| Operating Weight (Steel shoe) | 7,190 kg | p. 261 |
| Operating Weight (Road liner) | 7,220 kg | p. 261 |
| Tightening Torque (M16 bolt) | 235-285 N·m | p. 197 |
| Tightening Torque (M24 bolt) | 785-980 N·m | p. 197 |
Komatsu PC78US-6 Common Problems This Manual Covers
Komatsu PC78US-6 engine oil pressure monitor lamp lights up or stays on after engine startup
Stop the engine and check the oil pressure entry in the Troubles and Actions charts starting on page 172. Verify engine oil level and top up; a full refill takes 7 liters per page 245. If the filter is past due, replace the engine oil filter cartridge on the 500 hour interval listed on page 192.
Manual Section: Troubles and Actions p. 172Machine monitor panel displays error code E02, E03 or E05 during normal operation
Record the exact code shown on the monitor before shutting down. Check it against the electronic control system chart in the Troubles and Actions section beginning on page 172, and follow the action listed for E02, E03 or E05. Clear the cause, then restart and confirm the code no longer displays.
Manual Section: Troubles and Actions p. 172Track tension too loose with excess sag measured on steel or rubber shoes
Measure track deflection a at the point shown in the track tension procedure. Steel shoes should read 10 to 30 mm (0.4 to 1.2 in) per page 211; rubber shoes should read 1 to 3 mm (0.039 to 0.118 in) per page 215. Adjust tension until the reading falls in range, then measure again.
Manual Section: Maintenance p. 211Hydraulic pump making abnormal noise at startup after the hydraulic oil has been changed
Remove trapped air from each point the manual lists: the pump, between pump and tank, the LS circuit, cylinders, swing motor, swing PPC circuit, travel motor and attachments. If the noise continues after bleeding, check the pump noise and hydraulic oil temperature entries in the chassis troubleshooting chart.
Manual Section: Air Bleeding Hydraulic SystemEngine fails to start or the starting motor turns over slowly when the key is turned
Check battery charge first and follow the discharged battery procedure in Troubles and Actions on page 172. Verify the pre-heating system operates in cold weather before cranking. If the machine ran out of fuel, follow the running out of fuel steps, and replace the fuel filter cartridge on the 500 hour interval from page 192.
Manual Section: Troubles and Actions p. 172Frequently Asked Questions
What do Komatsu PC78US-6 error codes E02, E03, and E05 mean?
Error code E02 indicates a pump control system error, E03 indicates a swing brake system error, and E05 indicates a governor system error. For E02, ensure the emergency pump drive switch is set to the ON position. For E03, turn the swing brake cancel switch ON to release the brake. For E05, the fuel adjusting dial is inoperative; call for inspection immediately. p. 185
How do I change the operating pattern on a Komatsu PC78US-6?
To change the operating pattern, set the machine in the parking posture, stop the engine, and set the safety lock lever to the LOCK position. Open the inspection cover on the left side of the machine, loosen the wing nut (1), move lever (2) to the desired pattern, and tighten the wing nut. Ensure the operating pattern card in the cab matches the selected pattern. p. 276
What are the replacement specifications for fuel filters and water separator elements on the Komatsu PC78US-6?
The fuel filter cartridge (600-311-7460) should be replaced every 500 hours of service. The water separator element (21W-04-41480) does not have a specific replacement interval listed, but should be inspected and maintained as needed. p. 192
What is the correct cooling fan belt deflection for the PC78US-6?
The standard deflection for the cooling fan belt is approximately 8 mm (0.3 in) when pressed with a thumb force of approximately 58.8 N (6 kgf) at the midpoint between the alternator pulley and the fan pulley. p. 241
What is the hydraulic tank refill capacity on the Komatsu PC78US-6?
The refill capacity for the hydraulic tank is 64 liters (16.91 US gal). p. 193
What exactly do I receive with this Komatsu PC78US-6 manual?
This is a 289-page searchable PDF ready for immediate download. Works on any device, so pull it up on your phone while you're under the hood. No shipping, no waiting.
Does this Komatsu PC78US-6 manual allow printing?
Yes. Print a single page or a chapter for your own shop use, on letter or A4.
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