A travel motor weeping oil behind the sprocket, or a swing that drifts after you center the lever: that is the job waiting on your K903-II. The Kobelco K903-II shop manual PDF (S5LE0004E-01 NA) answers it in 554 pages written for this hydraulic excavator. Hydraulic circuit diagrams trace the bucket, arm, boom, travel and swing preferential circuits, wiring diagrams lay out the engine and pilot control systems, and troubleshooting charts sort faults by drive, hydraulic and swing system. Roughly half the book goes to component overhaul: pump, swing control valve, both hydraulic motors, swivel joint and cylinders. Check bucket port relief against the 190 to 230 kgf/cm² (2,702 to 3,271 psi) window, then torque 15x2.0 tube fittings to 15 ± 2 kgf-m (108 ft-lbs). Out here it's you, the machine, nobody to ask. Bookmarked by section and text-searchable, this file is yours once bought, kept for this K903-II as long as it runs.
What's Inside This Kobelco K903-II Manual
| System | Pages | Key Topics |
|---|---|---|
| Specification | 8-25 | General Dimensions, Specifications and Performance, Working Range of Attachments |
| Location and Weight of Components | 26-33 | Location of Components, Weight of Components, Transportation Weight |
| Maintenance Standards and Test Procedures | 34-63 | Hydraulic Pressure, Cylinder Speed, Cylinder Oil-Tightness |
| Troubleshooting | 64-85 | Drive System, Hydraulic System, Swing System |
| Working Standards | 86-89 | Tightening Torques for Capscrews, Tightening Torques for Nuts and Sleeves |
| Systems - Drive System | 90-105 | Power Plant, Pump Connection, Removal and Installation of Hydraulic Pump, Removal and Installation of Coupling, Removal and Installation of Engine |
| Systems - Hydraulic System | 106-143 | Hydraulic Circuit Diagram, Functional Description of Hydraulic Circuits, Bucket Circuit, Arm Circuit, Boom Circuit, Travel Circuit, Swing Preferential Circuit |
| Systems - Swing System | 144-165 | Swing System Drive Piping, Swing Grease Bath, Removal and Installation of Swing Control Valve, Removal and Installation of Swing Motor |
| Systems - Travel System | 166-221 | Construction of Lower Machinery, Track Link, Upper Roller, Lower Roller, Idler and Track Spring, Removal and Installation of Travel Motor, Removal and Installation of Sprocket |
| Systems - Attachments | 222-251 | Attachment System and Function, Backhoe Attachments, Removal and Installation of Attachments, Clearance Between Pin and Bushing, Adjusting Clearance Between Bucket and Arm |
| Systems - Control System | 252-285 | Engine Control System, Travel Control System, Hydraulic Control System, Pilot Valve, Flow Divider Valve |
| Components | 286-287 | Hydraulic Pump |
| Hydraulic Pump | 288-319 | |
| Swing Control Valve | 320-351 | |
| Control Valve | 352-457 | Pilot Valve, Hydraulic Motor (Swing) |
| Hydraulic Motor | 458-499 | Hydraulic Motor (Travel), Construction and Function, Disassembly and Assembly, Maintenance Standards, Troubleshooting |
| Swivel Joint | 500-511 | |
| Hydraulic Cylinder | 512-535 | |
| Reduction Unit | 536-554 | Reduction Unit (Swing), Major Specifications, Construction and Function, Disassembly and Assembly |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Filter, return (20) filtration rating | 20 μm | p. 110 |
| Port relief valve for bucket pressure | 190 kgf/cm² (2,702 psi) to 230 kgf/cm² (3,271 psi) | p. 39 |
| Tightening torque for 10x1.5 tube size | 6 ± 1 kgf-m (43.3 ± 7.2 ft-lbs) | p. 89 |
| Tightening torque for 15x2.0 tube size | 15 ± 2 kgf-m (108 ± 14.4 ft-lbs) | p. 89 |
| Displacement capacity | 37.3cc/rev. x 2 (0.0098gal/rev x 2) | p. 290 |
| Rated pressure | 200kg/cm² (2844 psi) | p. 290 |
| Clearance between piston rod and rod bushing | 0.25mm (0.009in) | p. 530 |
| Limit of bend for the piston rod | 1mm/1m (0.039in/3ft3in) | p. 530 |
| Travel speed | 3.9 km/hr (2.48 MPH) | p. 12 |
| Engine rated output power | 55 PS/2200 r.p.m | p. 12 |
| Fully equipped weight | 6,600 kg (14,550 lbs) | p. 29 |
| Engine oil volume (Upper Roller) | 50 c.c. (0.113 gal) | p. 175 |
Kobelco K903-II Common Problems This Manual Covers
Kobelco K903-II unusual noise coming from the pump connection between the engine and hydraulic pump
Remove the dust plug under the engine flywheel and check for rubber pieces or particles, following the page 66 chart. Particles mean the coupling element is broken, so disassemble and repair. If it is clean, check the coupling hub spline for wear and the hub fastening setscrew for slack. Then replace the hub or retighten the setscrew.
Manual Section: Drive System Troubleshooting p. 66Hydraulic oil temperature rising abnormally high partway through a normal shift of digging and loading
Check hydraulic oil volume first and replenish specified oil to the standard level. Clean the oil cooler and clear anything blocking air circulation, then adjust fan belt tension or replace the belt. Test main relief, port relief and travel relief set pressures and readjust any that are below standard, per page 67. If the main relief is working very often, reduce the load.
Manual Section: Hydraulic System Troubleshooting p. 67Hydraulic pump cavitation occurring under load while working boom, arm and bucket functions
Check hydraulic oil volume and replenish specified oil to the standard level. Verify the oil viscosity is not too high, and replace it with oil of proper viscosity if it is. Clean the suction strainer. Then inspect the pump suction line for air intrusion and retighten or replace parts as the page 67 chart directs.
Manual Section: Hydraulic System Troubleshooting p. 67Hydraulic oil sample pulled from the tank looking cloudy instead of clear
Drop a hydraulic oil sample on a hot plate and check if foam comes up. Foam means water is mixed in: let the oil stand still, separate and dispose of the water, or replace the hydraulic oil. No foam means air is intruding: check the suction and return lines and eliminate the source, per page 67.
Manual Section: Hydraulic System Troubleshooting p. 67Upper structure keeps swinging after the swing lever is released and will not stop
Verify the swing control valve spool returns to neutral. If it does not, disassemble and replace the faulty return spring. Move the spool by hand, and disassemble and repair it if it is stuck. Check swing relief and main relief set pressures against standard, then repair or replace whichever valve is out of standard, following the page 70 chart.
Manual Section: Swing System Troubleshooting p. 70Travel power weak when tracking alone, with boom, arm and bucket still working at normal force
Measure travel boost pressure relief valve pressure and repair or replace the valve if it is out of standard. Check travel brake pressure, then travel motor drain rate. If both pass, remove the parking brake spring, draw out the piston, refit the cover and retest. If power changes, the brake piston is stuck or the release circuit is clogged with dirt (page 74).
Manual Section: Travel System Troubleshooting p. 73Frequently Asked Questions
How do I troubleshoot hydraulic problems on a Kobelco K903-II?
Troubleshooting hydraulic problems involves checking for cloudy oil, abnormal temperature rises, or cavitation. For cloudy oil, check for water contamination and replace the oil if necessary. If the temperature rises abnormally, check the oil volume, oil cooler, fan belt tension, and relief valve settings. For cavitation, check the oil volume, oil viscosity, suction strainer, and for air intrusion in the pump suction line. Detailed flowcharts are provided in the Troubleshooting section. p. 67
What are the hydraulic pressure specifications for a Kobelco K903-II?
The hydraulic pressure specifications for the K903-II are detailed in Table 1 on page 39. For example, the RH travel relief valve advance pressure is 250+5 kgf/cm² (3,555+71 psi). The main relief valve pressure is 200+5 kgf/cm² (2,844+71 psi). Other port relief valves for the arm, boom, and bucket have specific pressure settings ranging from 190 to 230 kgf/cm². p. 39
What are the replacement specifications for the main hydraulic pump on the Kobelco K903-II?
The main hydraulic pump for the K903-II is an A10V 40LV 1RS 7V 40LV-920-0 model. It has a displacement capacity of 37.3 cc/rev x 2 (0.0098 gal/rev x 2). The rated pressure is 200 kgf/cm² (2,844 psi) and the maximum pressure is 250 kgf/cm² (3,555 psi). The rated revolution is 2,200 r.p.m. p. 290
What is the tightening torque for the main relief valve on the K903-II?
The tightening torque for the main relief valve (22) on the K903-II control valve is 7 to 8 kgf-m (50.5 to 57.7 ft-lbs). p. 373
What is the engine oil volume for the upper roller on the K903-II?
The engine oil volume for the upper roller on the K903-II is 50 c.c. (0.0132 gal). p. 175
Do I get instant access to this Kobelco K903-II Shop Manual?
You get a 554-page searchable PDF that downloads instantly after checkout. Open it on your laptop, tablet, or phone, and bring it right to the shop floor.
Does this Kobelco K903-II manual allow printing?
Yes. It prints from any PDF reader, so run off the pages you need for your own repair work.
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