Part of the Hyundai Repair Manuals.
All 414 pages of this Hyundai R55W-7A shop manual PDF are dedicated to one machine: the R55W-7A wheeled hydraulic excavator, from the pump device to the rear axle. You get full hydraulic schematics tracing the main and pilot circuits, electrical circuit diagrams with connector pinouts and component locations, and troubleshooting charts for both hydraulic and electrical faults. Open the disassembly and assembly section and follow step-by-step teardowns of the main control valve, swing device, travel motor, gear box, steering valve, and both axles. Set the main relief valve to 220 kgf/cm2 (3130 psi) and torque the P1 pump port fitting to 6.0 to 7.0 kgf·m; the numbers are all here. No more chasing pilot pressure problems with borrowed guesses. Bookmarked, with a full text layer: type a spec, jump to the page, and get your excavator digging again.
What's Inside This Hyundai R55W-7A Manual
| System | Pages | Key Topics |
|---|---|---|
| General | 1-21 | Safety Hints, Specifications |
| Structure and Function | 22-83 | Pump Device, Main Control Valve, Swing Device, Travel Device, Rcv Lever, Rcv Pedal, Brake Pedal, Gear Box |
| Hydraulic System | 84-113 | Hydraulic Circuit, Main Circuit, Pilot Circuit |
| Electrical System | 114-166 | Component Location, Monitoring System, Electrical Circuit |
| Troubleshooting | 167-203 | Before Troubleshooting, Hydraulic and Mechanical System |
| Maintenance Standard | 204-233 | Operational Performance Test, Major Component |
| Disassembly and Assembly | 234-394 | Precaution, Tightening Torque, Pump Device, Main Control Valve, Swing Device, Travel Device, Gear Box, Steering Valve |
| Component Mounting Torque | 395-414 | Introduction Guide, Engine System, Electric System, Power Train, Structure, Work Equipment |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Main relief valve pressure | 220kgf/cm2 (3130psi) | p. 16 |
| Overload relief valve pressure | 240kgf/cm2 (3410psi) | p. 16 |
| Tightening torque for P1, P2, P3, A1-B9 ports | 6.0~7.0 kgf·m | p. 30 |
| Tightening torque for A10, B10, B11 ports | 6.0~7.0 kgf·m | p. 30 |
| Filter filtration accuracy | 10 μm or less | p. 27 |
| Filter change interval | 500 hours | p. 28 |
| Hydraulic oil viscosity range (recommended) | 15 ~ 150 mm²/s | p. 27 |
| Hydraulic oil viscosity range (maximum allowable) | 1000 mm²/s | p. 27 |
| Pilot circuit relief valve setting pressure | 30kgf/cm2 | p. 88 |
| Solenoid valve resistance | 15~25 Ω | p. 143 |
| Clearance between piston outside dia and cylinder block inside dia | 0.050mm | p. 222 |
| Axial play of the piston and piston shoe | 0.2mm | p. 222 |
Hyundai R55W-7A Common Problems This Manual Covers
Hyundai R55W-7A all hydraulic functions weak, boom and bucket slow under load
Test main pump delivery pressure with a gauge on the pump outlet at high idle. If readings fall below the main relief valve setting of 220 kgf/cm2 (3130 psi) listed on page 16, adjust or replace the relief valve, then work through the hydraulic troubleshooting procedures starting on page 172.
Manual Section: Hydraulic and Mechanical System Troubleshooting p. 172Machine creeps or drifts with pilot valve in neutral, bucket slowly lowers
Check for internal cylinder leakage first: raise the boom, shut the engine down, and watch for drift. Inspect the overload relief valves next; they should hold 240 kgf/cm2 (3410 psi) per the spec on page 16. If a valve opens below that figure, replace it and retest drift in neutral.
Manual Section: Hydraulic and Mechanical System Troubleshooting p. 16Hydraulic oil temperature warning lamp and buzzer come on during normal digging
Verify hydraulic oil level and top up before anything else; the buzzer trips once oil passes 105°C. Clean debris packed between the oil cooler and radiator with compressed air. Confirm oil viscosity sits in the 15 to 150 mm²/s range shown on page 27, and replace hydraulic filters every 500 hours.
Manual Section: Electrical System Troubleshooting p. 27Boom and arm controls unresponsive or erratic, suspect pilot pressure or solenoid
Measure pilot primary pressure at the pilot line; the relief setting is 30 kgf/cm2 per page 88. If pressure checks good, test the solenoid coil with a multimeter: resistance should read 15 to 25 ohms as listed on page 143. Replace the coil if it reads open or out of range.
Manual Section: Hydraulic System p. 88Hydraulic hose fittings leaking at main control valve ports after hose replacement
Torque the main work ports P1 through B9 to 6.0 to 7.0 kgf·m following the port table on page 30, and take the tank return and pilot port figures from the same table. Replace any O-ring that shows flattening before you button it back up.
Manual Section: Structure and Function p. 30Frequently Asked Questions
What is the torque specification for the swing bearing mounting bolts on a Hyundai R55W-7A?
The torque specification for both the swing bearing upper and lower mounting bolts is 29.7 ± 4.5 kgf·m (215 ± 32.5 lbf·ft). p. 237
What are the replacement criteria for the main relief valve in the main control valve?
The main relief valve should be replaced if there is external rusting or damage, if the contacting face of the valve seat or poppet is damaged, if the spring is abnormal, or if the O-rings, back-up rings, and seals are worn. In general, 100% replacement of O-rings, back-up rings, and seals is recommended during disassembly. p. 224
What is the standard engine speed for the R55W-7A at low idle and high idle?
The standard engine speed for the R55W-7A is 1050 ± 100 rpm at low idle and 2260 ± 50 rpm at high idle (M mode). p. 207
What is the procedure for bleeding air from the hydraulic pump after installation?
To bleed air from the hydraulic pump, loosen the air vent plug, start the engine and run at low idling until oil comes out from the plug, then tighten the plug fully. After this, run the engine at low idling for 3-5 minutes to circulate oil through the system. p. 241
What is the tightening torque for the main pump mounting bolts?
The main pump mounting bolts (M12 x 1.75) should be tightened to 14.7 ± 2.2 kgf·m (106 ± 15.9 lbf·ft). p. 237
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