Written for the MDI Yutani MD320B hydraulic excavator, this 454-page shop manual (OEM ID S5YC0002E) is the factory book for that one model. Hydraulic schematics trace the travel, boom, arm, bucket and swing circuits through to the negative control signal circuit. Troubleshooting charts sort faults by drive, swing, travel, attachment and electrical system, and the undercarriage chapter takes you through track links, rollers, idler and track spring, and the sprocket. On the main hydraulic pump, run the Symbol A socketscrews to 46 ± 3.0 kgf·m (331.9 ft.lbs), then set the Symbol F capscrews at 7 ± 0.7 kgf·m with Loctite #242. A guessed torque is how pump mounts work loose. You can search the text or jump by bookmark, then print the pages your job calls for and let them take the grease at the bench.
What's Inside This Mdi Yutani MD320B Manual
| System | Pages | Key Topics |
|---|---|---|
| Operation and Controls | 5-6 | Throttle Lever, Engine Stop Position, Low Idle Setting, Travel Control Lever, Pilot Valve Lever Stroke, Secondary Pressure |
| Specification | 7-22 | Names of Components, General Dimensions, Specifications and Performance |
| Location and Weight of Components | 23-28 | Location of Components, Weight of Components, Transportation Weight |
| Maintenance Standards and Test Procedures | 29-44 | Pressure Measurement and Adjustment, Cylinder Speed, Cylinder Oil-Tightness, Swing Performance, Travel Performance |
| Troubleshooting | 45-69 | Drive System, Hydraulic System, Swing System, Travel System, Attachment System, Electrical System |
| Tightening Torques for Capscrews and Nuts | 70-73 | Metric Coarse Screw Threads, Metric Fine Screw Threads, Nuts and Sleeves Tightening Torques |
| Systems Section Overview | 74-75 | Drive System, Hydraulic System, Swing System, Travel System, Attachments, Control System, Upper Frame, Electrical System |
| Drive System | 76-87 | Power Plant, Hydraulic Pump Removal and Installation, Coupling Removal and Installation, Engine Removal and Installation, Suction Stopper Detail |
| Hydraulic System | 88-106 | Hydraulic System Diagram, Travel Circuit, Boom Circuit, Arm Circuit, Bucket Digging, Swing Circuit, Negative Control Signal Circuit |
| Swing System | 107-116 | Swing System Operation, Swing Bearing, Swing Grease Bath, Swing Control Valve, Swing Motor, Swing Reduction Unit |
| Travel System | 117-149 | Lower Machinery Construction, Travel System Function, Track Link, Upper Roller, Lower Roller, Idler and Track Spring, Travel Reduction Unit, Sprocket |
| Attachments | 150-166 | Attachment System Functions, Backhoe Attachments, Bucket Removal and Installation, Arm Removal and Installation, Boom Removal and Installation, Pin and Bushing Clearance |
| Control System and Electrical System | 167-179 | Engine Control System, Travel Control System, Hydraulic Control System |
| Upper Frame | 180-194 | Fuel Tank, Removal and Installation of Counterweight, Removal and Installation of Cab |
| Electric System Diagram | 195-212 | Electrical System Diagram |
| Hydraulic Pump | 213-258 | Pump Control Curves, Pilot Valve |
| Control Valve | 259-330 | Main Relief Valve, Travel Relief Valve |
| Hydraulic Motor | 331-374 | Function of Brake Valve, Mounting Position of Changeover Valve |
| Swivel Joint | 375-388 | Thrust Plate, Slipper Ring, Square Ring |
| Hydraulic Cylinder | 389-408 | Tools and Jigs List |
| Reduction Unit | 409-441 | Planetary Shaft, Sun Gear, Pinion Shaft Assembly |
| Heavy Lift | 442-454 | Heavy Lift Modification |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| O ring port tightening torque (Symbol A) | 10.0-12.0 kgf·m (72-86 lbs/in²) | p. 176 |
| O ring port tightening torque (Symbol B) | 7.0-8.0 kgf·m (50-57 lbs/in²) | p. 176 |
| Tightening torque of socketscrew (Symbol A) | 46 ± 3.0 kgf.m (331.9 ± 21.6 ft.lbs) | p. 84 |
| Tightening torque of socketscrew (Symbol C) | 44 ± 4 kgf.m (318.1 ± 28.9 ft.lbs) | p. 84 |
| Tightening torque of radiator upper frame mounting capscrew (Symbol E) | 15 kgf.m (108 ft.lbs) | p. 85 |
| Adjusting dimension of fan and radiator shroud (Symbol F) | 15 ± 5 mm (0.59 ± 0.20") | p. 85 |
| Socket bolt fastening swing control valve | 7 ± 0.7 kgf·m (50.5 ± 5.1 ft-lbs) | p. 117 |
| Socket bolts fastening swing motor and swing reduction unit | 55 ± 5.5 kgf·m (397.6 ± 39.7 ft-lbs) | p. 117 |
| For swivel joint fastening nut | 16 ± 2 kgf.m (115 ± 14 ft.lbs) | p. 143 |
| For reduction unit mounting capscrews | 55 ± 5.5 kgf.m (397 ± 40 ft.lbs) | p. 143 |
| Clearance between piston rod and rod bushing | 0.25 mm (0.0098 in) | p. 405 |
| Allowable bend of the rod | 1 mm/1 m (0.039 in/3'3") | p. 405 |
Mdi Yutani MD320B Common Problems This Manual Covers
MDI Yutani MD320B engine starts but machine does not operate at all
Check hydraulic tank oil level and replenish to standard following page 47. A noisy pump means disassemble and repair it. Noise at the pump connection: remove the dust plug under the engine flywheel and look for coupling rubber particles. Verify primary pilot pressure, then check the gear pump, pilot relief valve and pilot piping for clogs or leaks.
Manual Section: Drive System Troubleshooting p. 47Hydraulic oil cooler or relief valve fault with hydraulic oil temperature rising abnormally
Check hydraulic oil volume and replenish specified oil to the standard level following page 49. Clean the oil cooler and clear anything blocking air circulation. Adjust fan belt tension or replace the belt. Test main relief, port relief and travel relief set pressures, and readjust any that read lower than standard. If the main relief valve is working very often, reduce the load.
Manual Section: Hydraulic System Troubleshooting p. 49Hydraulic pump suction strainer or suction line fault with cavitation occurring at the pump
Check hydraulic oil volume and replenish specified oil to the standard level following page 49. If oil viscosity is too high, replace it with oil of proper viscosity. Remove and clean the suction strainer. Inspect the pump suction line for air intrusion, then retighten the connections or replace parts.
Manual Section: Hydraulic System Troubleshooting p. 49Hydraulic tank oil sample appearing cloudy or contaminated when drawn for inspection
Drop an oil sample on a hot plate following page 49. Foaming means water is mixed in: separate and dispose of the water or replace the hydraulic oil. Bubbles rising from settled oil mean air is getting in, so check the suction and return lines. If the oil is past its replacement hours or the return filter is overdue, flush the system and replace them per page 50.
Manual Section: Hydraulic System Troubleshooting p. 49Swing control valve or swing motor fault with low swing speed in one or both directions
Measure secondary pilot pressure on LH and RH sides following page 51. If it is unequal, clean or repair clogged or leaking pilot piping, or repair the pilot valve. Check that the swing control valve spool moves smoothly by hand and clean its shuttle valve. Verify swing relief valve pressure and swing motor drain rate against standard values per page 52.
Manual Section: Swing System Troubleshooting p. 51Travel motor on one side losing speed with the machine curving during single travel operation
Swap the LH and RH travel relief valves following page 55 and see if the slow side changes over. Check the travel motor leak rate against standard. Remove the parking brake spring in the slower motor; if speed changes, the parking brake is not releasing, so disassemble and clean the pilot piping. Verify external pilot pressure and clean the control valve orifice.
Manual Section: Travel System Troubleshooting p. 55Frequently Asked Questions
What are the torque specifications for the MDI Yutani MD320B?
Tightening torques for capscrews and nuts are provided in Table 1 on page 72. For example, an M6 bolt (P=1) with no lubrication requires 0.45 ± 0.05 kgf·m (3.2 ± 0.4 ft-lbs), while an M36 bolt (P=4) with no lubrication requires 105 ± 10 kgf·m (757 ± 72.2 ft-lbs). p. 72
How do you troubleshoot an MD320B that will not start?
If the engine starts but the machine does not operate, check if the oil level in the hydraulic tank is within the standard level (page 47). If the oil level is correct, check if the primary pilot pressure is within the standard level; if not, the pilot relief valve may be faulty. p. 47
What is the engine oil volume for the Mitsubishi 6D22-T engine?
The engine oil volume for the Mitsubishi 6D22-T engine is 25 liters (6.6 gal) for the engine body, plus 4 liters (1.05 gal) for the filter and other components. p. 19
What is the standard clearance between the piston rod and rod bushing for the Mdi Yutani MD320B hydraulic cylinders?
The rod bushing must be replaced if the clearance between the piston rod and the rod bushing exceeds 0.25 mm (0.0098 in), the service limit for the hydraulic cylinder. p. 405
What is the procedure for adjusting the low revolution (LO) of the engine?
To adjust the low revolution (LO), loosen the nut (1) fastening the control cable and adjust the length of the cable (C). Refer to the service standard of the control system for the specific length (C). p. 32
How quickly can I access this MDI Yutani MD320B manual after buying?
You download the Shop Manual yourself: 454 pages, searchable PDF, available immediately. Keep a copy on every device you use.
Is this MDI Yutani MD320B manual print-friendly?
You can. Print the sections you want for your own use and keep the file as your backup.
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