Part of the Doosan Repair Manuals.
Working on a DX420LC? This 900-page Doosan Daewoo DX420LC Shop Manual PDF (OEM #K1009096E) walks you through every system on the track excavator, from the swing bearing to the KVMG-400-DA control valve. Inside: a full electrical schematic set, hydraulic schematics with complete circuit routing, and a dedicated troubleshooting, testing and adjustment section covering pilot pressure and the power mode valve. You also get teardown procedures for the main pump, swing motor, travel motors, and all three cylinders. Torque the fuel filter head plug to 27 kg-m (200 ft lb) and fill the 550-liter fuel tank knowing your numbers came straight from Doosan. No more chasing hydraulic faults with a pressure gauge and a hunch. Bookmarked with a full text layer; type a spec, jump to the section, get back on the sticks.
What's Inside This Doosan Daewoo DX420LC Manual
| System | Pages | Key Topics |
|---|---|---|
| Safety Precautions | 4 | Track Excavator Safety |
| Safety | 5-52 | Applicable Models, To the Operator of a Doosan Daewoo Excavator, General Safety Essentials, Location of Safety Labels, Summary of Safety Precautions for Lifting in Digging Mode |
| Specifications | 53-82 | Specification for DX420LC |
| General Maintenance Procedures | 83-102 | Applicable Models, Welding Precautions and Guidelines, Hydraulic System - General Precautions, Maintenance Service and Repair Procedure, Hydraulic System Cleanliness and Oil Leaks |
| Standard Torques | 103-118 | Applicable Models, Torque Values for Standard Metric Fasteners, Torque Values for Standard U.S. Fasteners, Type 8 Phosphate Coated Hardware, Torque Values for Hose Clamps |
| Upper Structure | 119-218 | Cabin, Counterweight, Fuel Tank, Swing Bearing, Swing Reduction Gear |
| Lower Structure and Chassis | 219-298 | Track Assembly, Air Conditioner SP000025 |
| Engine and Drive Train | 299-308 | Drive Coupling (Main Pump) |
| Hydraulic System Troubleshooting, Testing and Adjustment | 309-348 | Hydraulic Schematic, Working Components, Pilot Pressure, Power Mode Valve, Boom/Front Priority Valve |
| Accumulator | 349-356 | Gas-Charged Storage, Precharge Pressure, Diaphragm, P1 Rated Pressure |
| Center Joint (Swivel) | 357-370 | Hydraulic Oil Flow, 360-Degree Rotation, Disassembly, Reassembly |
| Cylinders | 371-400 | Boom Cylinder, Arm Cylinder, Bucket Cylinder, Rod Stopper, Cushioning |
| Swing Motor | 401-436 | Rotary Power, Relief Valve, Parking Brake, Makeup Check Valve, Time Delay Valve |
| Travel Motor (with Gearbox) | 437-492 | Two-Stage Planetary Gearbox, Brake Valve, Capacity Control, Overload Valve |
| Main Pump | 493-550 | Pump Regulator, Rotary Groups, Auxiliary Drive, Control Module, Tightening Torques |
| Control Valve (Kvmg-400-Da) | 551-742 | Neutral Passage, Signal Passage, Anti-Drift Valve, Main Relief Valve, Overload Relief Valve |
| Electrical System | 743-870 | Electrical System SP000269, Electrical Schematic (DX420LC) |
| Attachments | 871-900 | Boom and Arm, Bucket |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Fuel tank capacity | 550 liters (145 U.S. gal) | p. 149 |
| Bolt torque for fuel filter head plug | 27 kg•m (200 ft lb) | p. 154 |
| Filter cleaning interval | 500 hours | p. 267 |
| Hydraulic reservoir return line and pilot circuit filter rating | 10 micron | p. 319 |
| Reservoir intake strainer micron rating | 177 micron | p. 319 |
| Braking Torque | 644 Nm | p. 443 |
| Brake Release Pressure | 15.7 kg/cm2 | p. 443 |
| Outer dia. of piston (d max - d min) | 0.01 mm | p. 459 |
| Inner dia. of cylinder bore (D max - D min) | 0.01 mm | p. 459 |
| Shaft wear depth for reusability | less than 0.05mm | p. 460 |
| Hydraulic System Capacity | 420 liters | p. 68 |
| Hydraulic Reservoir Capacity | 265 liters | p. 68 |
Doosan Daewoo DX420LC Common Problems This Manual Covers
Doosan Daewoo DX420LC hydraulic functions weak and slow, pump whining and oil overheating under load
Check the hydraulic oil level and condition first; the reservoir holds 265 liters and low oil lets the pump pull air. Drop the suction strainer and clean it, that intake screen is 177 micron and plugs with sludge. Replace the 10 micron return filter, then work through the troubleshooting procedures starting on page 311 before condemning the pump.
Manual Section: Hydraulic System Troubleshooting, Testing and Adjustment p. 311Travel motor will not rotate, machine will not travel or one track drags
Verify the parking brake releases before condemning the motor; pilot pressure at the brake port must reach 15.7 kg/cm2, the spec is on page 443. Measure case drain pressure next, anything over 2 kg/cm2 means internal leakage past the rotary group. Drain the planetary gearbox and check the oil for metal before reassembly.
Manual Section: Travel Motor (with Gearbox) p. 437Hydraulic oil temperature climbs fast under load, relief valves hissing during hard digging
Test main relief pressure at the pump with a gauge; the spec on page 74 is 320 kg/cm2 normal and 350 kg/cm2 in pressure-up mode. A relief valve stuck low dumps flow across the seat and cooks the oil. Clean the cooler fins with compressed air and check fan drive condition while you are in there.
Manual Section: Hydraulic Problems TroubleshootingEngine cranks slowly or will not start at all, especially on cold mornings
Load test the batteries and clean both ground cable connections before blaming the starter. Trace the crank circuit using the wiring diagram if the relay clicks but nothing turns. If it spins but will not fire, bleed air from the fuel system, replace both fuel filters, and check the pickup in the 550 liter tank for sludge.
Manual Section: Electrical SystemMetallic glitter in hydraulic oil, filters loading up with grey paste at every service
Drain a sample from the reservoir bottom into a clean jar and let it settle; grey paste or metal flake means the rotating group is eating itself. Tear the pump down and measure piston to cylinder bore clearance against the 0.037 to 0.050 mm spec on page 459. Flush all 420 liters of system oil before restart.
Manual Section: Main Pump p. 493Frequently Asked Questions
How do I check for fault codes on the Doosan DX420LC?
To start the self-diagnosis, turn the starter switch to the ON position, set the temperature to 25°C or 77°F, and press the SEL switch more than 3 times in 5 seconds while pressing the A/C switch. The auto-diagnosis will start, and error codes will blink in a 0.5-second cycle on the display. p. 847
What is the procedure for resetting the operating hours for filters and oils?
To reset the operating hours, navigate to the 'Filter / Oil Info' mode in the main menu. After changing the filter and oil, use the reset function to clear the operating hours so that the time until the next service interval can be tracked accurately. p. 779
What is the tightening torque for the main relief valve cap on the control valve?
When reassembling the main relief valve, the cap (8) should be tightened to a torque of 9.48 - 11.01 kg•m (69 - 80 ft lb). Ensure the installation portion is clean before installing. p. 608
What is the fuel tank capacity for the DX420LC?
The fuel tank capacity for the DX420LC is 550 liters (145 U.S. gal). p. 149
What is the tightening torque for the counterweight mounting bolts?
The mounting bolts for the counterweight on the DX420LC should be torqued to 250 kg•m (1,807 ft lb). p. 140
How will I receive this Doosan Daewoo DX420LC Shop Manual?
A single searchable PDF file of 900 pages, downloadable right after payment. Nothing ships, nothing waits in the mail.
Am I able to print pages from this Doosan Daewoo DX420LC manual?
Yes, print as many copies as you want, and there are no restrictions. Many mechanics print the section they need and bring it to the shop floor.
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