Part of the Hyundai Repair Manuals.
All 142 pages of this Hyundai R28-7 (R28-7) Service Manual PDF cover one machine: your R28-7 crawler excavator, from the main pump down to the track rollers. You get full hydraulic schematics, electric circuit diagrams for the starter and alternator systems, and step-by-step teardown procedures for the main pump, control valve, all three pilot valves, slew motor, and travel motor. A full troubleshooting section walks you through travelling and slewing faults, and page after page of maintenance standards backs up every rebuild. Set main relief pressures P1 and P2 to 20.6 MPa, port relief to 23.5 MPa, and confirm unload pump pressure at 2.9 MPa before you button up the hydraulics. No more chasing hydraulic faults with a gauge and a hunch. Bookmarked with a full text layer; download it, pull up any spec by keyword, and get back on the tracks.
What's Inside This Hyundai R28-7 Manual
| System | Pages | Key Topics |
|---|---|---|
| Precautions on Maintenance | 6 | Correct Operation, Safety Check, Preparation, Disassembly, Assembly |
| Outline | 7-24 | Location of Serial Number, Name of Each Part, Dimensions and Specifications |
| Attachment | 25-32 | Measuring the Natural Fall of the Attachment, Measuring Attachment Cylinder Speed, Standard of Maintenance |
| Engine | 33-44 | Specification, Inspection and Maintenance Procedures |
| Main Pump | 45-52 | Removing and Installing the Pump, Performance Test |
| Hydraulic Oil Filter | 53-58 | Hydraulic Oil Filter Specifications, Maintenance Procedure |
| Control Valve | 59-66 | Disassembly and Assembly, Structure of the Relief Valve, Precautions for Handling |
| Joystick (Pilot Valve) | 67-69 | Specification, Structure, Joystick Valve Assembly, Casing, Spool |
| Pilot Valve (1) (Travel) | 70-73 | Specification, Structure, Pilot Valve Assembly, Casing, Spool |
| Pilot Valve (2) (Swing, PTO) | 74-77 | Specification, Structure, Pilot Valve Assembly, Casing, Pusher Assembly |
| Pilot Valve (3) (Dozer) | 78-81 | Specification, Structure, Dozer Pilot Valve, Pusher Assembly, Body Assembly |
| Slew Motor | 82-87 | Specification, Structure, Slew Bearing, Slew Case, Relief Valve |
| Travel Motor | 88-93 | Specification, Structure, Hydraulic Motor, Reduction Gear, Pinion Gear |
| Hydraulic Cylinder | 94-99 | Disassembly and Assembly, Assembly Procedures |
| Swivel Joint | 100-103 | Specification, Structure, Swivel Joint Assembly, Cylinder, Slipper Seal |
| Crawler | 104-111 | Crawler (Steel) and Track Frame, Rubber Crawler Total Length 3, 960 Mm and Width X Pitch, Removing and Installing the Crawler, Track Frame Spring |
| Spring Case and Grease Cylinder | 112-115 | Structure, Specification of Spring, Disassembly and Assembly, Adjust Cylinder, Spring Case |
| Idler | 116-117 | Standard of Maintenance, Lubricating Oil |
| Sprocket | 118-121 | Disassembly and Assembly, Removing the Sprocket, Installing the Sprocket, Standard of Maintenance |
| Track Roller | 122-123 | Standard of Maintenance, Lubricating Oil |
| Carrier Roller | 124-125 | Standard of Maintenance, Lubricating Oil |
| Electrical Equipment | 126-129 | Structure and Function, Electric Circuit Diagram, Failure and Remedy, Starter System, Alternator System |
| Troubleshooting | 130-142 | Troubleshooting Procedures, Travelling System Troubleshooting, Slewing System Troubleshooting |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Main relief pressure P1 | 20.6 MPa | p. 24 |
| Main relief pressure P2 | 20.6 MPa | p. 24 |
| Battery | 12V × 50 AH | p. 34 |
| Line filter filtration accuracy | 10µ | p. 55 |
| Line filter proof pressure | 0.7 MPa | p. 55 |
| Suction filter oil temperature | -20°C~120°C | p. 55 |
| Pump weight | 23 kg | p. 46 |
| Pump mounting bolt tightening torque | 90~115 N·m | p. 48 |
| Tightening torque for mounting roller | 325 N·m | p. 123 |
| Hydraulic Oil Tank Capacity | 50.5L | p. 11 |
| Engine Oil Capacity | 4.5L | p. 11 |
| Fuel Tank Capacity | 42L | p. 11 |
Hyundai R28-7 Common Problems This Manual Covers
Hyundai Robex 28-7 hydraulics weak, boom and bucket slow, all functions lose power under load
Check the hydraulic tank level first; low oil in the 50.5 L tank pulls air and kills every circuit. Gauge main relief pressure at P1 and P2 against the 20.6 MPa spec on page 24. If pressure stays low, pull and clean the suction strainer, then work the troubleshooting chart starting on page 131.
Manual Section: General Hydraulic Troubleshooting p. 131Upper structure slew speed extremely slow, grinding noise from slew motor, swing binds mid rotation
Test the slew circuit relief pressure against the 13.2 MPa overload setting listed on page 83. If pressure checks good, drop the slew motor and inspect the pinion and slew bearing gear teeth for chipped or worn flanks, following the disassembly steps starting on page 82. Replace a scored pinion before it ruins the bearing.
Manual Section: Slew Motor p. 82Machine meanders during straight travel, one track weak, fails to hold position on incline
Check track tension at the grease adjuster cylinder covered on page 112; a loose track lets the machine walk crooked. Drain each travel motor reduction gear and refill with 600 cc of gear oil. If one side still lags, measure sprocket and roller wear against the crawler maintenance standards starting on page 104.
Manual Section: Travelling System TroubleshootingEngine cranks slowly or starter pinion will not engage, no start on cold mornings
Test battery voltage and load capacity first; the machine runs a 12V, 50 AH battery, spec on page 34. Clean the ground strap and battery terminal connections, then work through the starter failure and remedy tables in the electrical section starting on page 126. If the pinion still hangs up, pull the starter and bench-test the solenoid.
Manual Section: Electrical Equipment p. 126Boom drops slowly under load with controls in neutral, cylinder drifts down overnight
Check port relief pressure against the 23.5 MPa spec on page 24; a weak relief bleeds the boom down. Adjust at the control valve, where one turn of the port relief adjuster changes pressure 15.7 MPa, per the procedure on page 66. If pressure holds, reseal the boom cylinder following the assembly steps starting on page 94.
Manual Section: Control Valve p. 66Frequently Asked Questions
What are the torque specifications for the hydraulic piping fittings on the Hyundai Robex 28-7?
The tightening torque for hydraulic piping depends on the screw type and size. For PT screws, the torque ranges from 36 N·m for 1/4 size to 400 N·m for 1 1/2 size. For PF screws, the torque ranges from 27-30 N·m for 1/4 size to 126-140 N·m for 1 size. p. 19
How do I check the hydraulic pressure on the Hyundai Robex 28-7?
To check the hydraulic pressure, install a pressure gauge between the pump and control valve in the measuring position. Raise the hydraulic oil temperature to 50-60°C, set the engine to rated speed, and operate the control lever to read the pressure gauge at the stroke end. p. 66
What are the replacement specifications for the hydraulic oil filter?
The hydraulic line filter has a filtration accuracy of 10µ, a filtration capacity of 125 l/min (Max.), and a proof pressure of 0.7 MPa. It is recommended to inspect and maintain line filters after the first 100 service hours, then every 500 service hours. p. 56
What are the replacement specifications for the suction strainer?
The suction filter has a grain size of 150 mesh and a filtration capacity of 330 l/min (Max.). It is designed to operate within an oil temperature range of -20°C to 120°C. p. 55
What is the correct valve clearance for the engine?
The valve clearance for both inlet and exhaust valves on the S3L2 engine should be 0.25 mm (0.0098 in.) when the engine is cold. p. 37
What format is this Hyundai Robex 28-7 manual in?
All 142 pages arrive as one searchable PDF at checkout. Read it at the desk, then take the phone out to the machine.
Am I free to print this Hyundai Robex 28-7 Service Manual?
No restrictions at all. Print individual pages, full chapters, or the entire manual. The PDF is completely unlocked.
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