Part of the Hyundai Repair Manuals.
Every one of this manual's 547 pages targets one machine: the Hyundai HL780-3 wheel loader. If you have been hunting a Hyundai HL780-3 service manual PDF with real factory data, this is it. Inside: electrical circuit diagrams for the starting circuit, monitoring system, and connectors, hydraulic schematics tracing the main pump, flow amplifier, and remote control valve, plus full troubleshooting sections for the power train, brakes, and steering. You also get exploded views of the major assemblies and page after page of step-by-step disassembly and reassembly procedures. Set the pressure relief valve to 3.1 kgf·m (22.4 lbf·ft) and confirm torque converter stall speed lands between 2070 and 2210 rpm. No more chasing wiring faults with a multimeter and a prayer. Bookmarked front to back; type any spec into the search bar and pull it up on whatever device is in the cab.
What's Inside This Hyundai HL780-3 Manual
| System | Pages | Key Topics |
|---|---|---|
| General | 9-32 | Safety Hints, Specification, Operational Checkout Record Sheet |
| Engine | 33-51 | Cooling System, Lubrication System |
| Power Train System | 52-247 | - |
| Brake System | 248-283 | Brake System Structure and Function, Brake Pump, Brake Valve, Cut Off Valve, Brake Accumulator, Pressure Switches, Service Brake |
| Group 4 Disassembly and Assembly | 284-291 | - |
| Group 1 Structure and Function | 292-309 | Steering System, Flow Amplifier |
| Group 2 Operational Checks and Troubleshooting | 310-317 | - |
| Group 3 Tests and Adjustments | 318-391 | Hydraulic Oil Clean Up Procedure Using Portable Filter Caddy, Steering Pump, Flow Amplifier, Steering Cylinder |
| Work Equipment | 392-473 | Hydraulic System Outline, Remote Control Valve, Boom Section Operation, Hydraulic Oil Tank, Main Pump |
| Electrical System | 474-547 | Starting Circuit, Monitoring System, Switches, Electrical Component Specification, Connectors, Troubleshooting |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Torque converter stall rpm | 2070 ~ 2210rpm | p. 88 |
| Torque M12x1.5 | 2.9 ± 0.31kgf·m | p. 265 |
| Torque M16x1.5 | 4.1 ± 0.51kgf·m | p. 265 |
| Tightening torque for pressure relief valve | 3.1 ± 0.3kgf·m (22.4 ± 2.2lbf·ft) | p. 358 |
| Tightening torque for plug or throttle check valve | 1 ± 0.3kgf·m (7.2 ± 2.2lbf·ft) | p. 356 |
| Tightening torque for orifice | 0.5 ± 0.1kgf·m (3.6 ± 0.7lbf·ft) | p. 356 |
| Tightening torque for orifice in housing | 0.5 ± 0.1kgf·m (3.6 ± 0.7lbf·ft) | p. 356 |
| Control port 5 pressure | 22bar | p. 407 |
| Pilot oil supply unit pressure setting | 3MPa | p. 419 |
| Engine Rated Gross Horse Power | 340 ps | p. 23 |
| Engine Oil Quantity | 40 L | p. 23 |
| Main Pump Capacity | 100 cc/rev | p. 23 |
Hyundai HL780-3 Common Problems This Manual Covers
Hyundai HL780-3 hydraulic pump whining and cavitation noise, bucket and boom functions slow when cold
Check hydraulic oil level and viscosity first; cold, thick oil starves the pump inlet. Inspect the suction line for pinched hose, loose clamps, or air leaks, and pull the suction strainer for cleaning. Verify pump output against the 213 L/min maximum flow spec on page 444; a worn pump will not make flow.
Manual Section: Hydraulic System Troubleshooting p. 444Boom float detent won't engage or lever kicks back out of float position
Test pilot pressure at the remote control valve; the float detent needs 2.2 MPa (22 bar) to hold, spec on page 450. Verify the pilot oil supply unit is delivering its 3 MPa setting. If both pressures check good, pull the loader control valve spool and inspect for binding or scoring in the bore.
Manual Section: Work Equipment p. 450All hydraulic functions weak under load, boom stalls before reaching full height with warm oil
Check system relief pressure with a gauge; spec is 210±5 kg/cm² (2987±70 psi) per page 448. Low readings point to a worn main pump or a relief valve stuck partly open. Test the boom raise circuit against its 250±5 kg/cm² setting before condemning the pump, then adjust or replace the relief cartridge.
Manual Section: Hydraulic System Troubleshooting p. 448Steering wheel hard to turn and hydraulic oil running hot during truck loading
Remove the priority valve spool and confirm the orifice plugs are installed in both spool ends; a missing plug restricts flow and builds heat. Run the operational checks starting on page 310 to confirm the restriction first. Reinstall the LS-connection orifice at 1 ± 0.3 kgf·m (7.2 ± 2.2 lbf·ft) per page 357.
Manual Section: Group 2 Operational Checks and Troubleshooting p. 310Service brakes weak and pedal spongy, brakes drag after a hydraulic oil contamination event
Drain and flush the brake circuit; contaminated oil scores the cut-off valve and accumulator seals. Bleed at each wheel until fluid runs clean, then torque the M12x1.5 line fittings to 2.9 ± 0.31 kgf·m per page 265. Verify brake pump output matches its 16 cc/rev rating before returning the machine to service.
Manual Section: Brake System p. 265Frequently Asked Questions
What is the hydraulic oil temperature warning on the HL780-3?
The hydraulic oil temperature warning lamp operates and the buzzer sounds when the temperature of the hydraulic oil exceeds 105°C (221°F). If this lamp turns on, you should check the hydraulic oil level and inspect for debris between the oil cooler and the radiator. p. 499
What are the replacement specifications for the hydraulic pump?
The pump output listed applies to a new pump. A 20% tolerance below the specified rating is permissible; however, if the pump output is more than 20% below specification, the pump must be replaced and not rebuilt. p. 100
What is the torque specification for the main pump mounting screws?
The tightening torque for the main pump mounting screws (70) is 9 kgf·m (65 lbf·ft), and for the screws (80) it is 40.5 kgf·m (293 lbf·ft). p. 456
What is the procedure for bleeding the hydraulic brake system?
Two people are required to bleed the brake system. Push and hold the brake pedal down until the bleeding procedure is complete, then open the bleed screw on the differential and axle assembly until hydraulic oil starts to flow. Close the bleed screw when the oil is free of air and release the brake pedal. p. 283
What is the rated pressure for the clutch cut off pressure switch?
The rated setting pressure for the clutch cut off pressure switch is 25 kgf/cm². p. 97
What exactly do I receive with this Hyundai HL780-3 Service Manual?
A single searchable PDF file of 547 pages, downloadable right after payment. Nothing ships, nothing waits in the mail.
Is printing allowed for this Hyundai HL780-3 Service Manual?
Zero restrictions. The PDF is DRM-free. Print whatever sections you need to take out to the shop. Standard letter or A4 paper works.
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