If your wheel loader carries a WA420-3 plate, this 946-page Komatsu WA420-3 shop manual PDF (factory number VEBM470104) was written for it, laid out in the original five sections from General through Maintenance Standard. Structure and Function fills roughly a third of the book, where hydraulic schematics trace the steering and work equipment circuits and wiring diagrams map transmission control, brakes and the air conditioner. Testing and Adjusting is built around standard value tables for engine, chassis and electrical parts, so you compare a reading against the factory number before any teardown begins on the transmission, clutch packs or parking brake. Check that the A/C low pressure switch cuts out at 2.0 bar, and torque 12 mm bolts to 112 ± 9.8 Nm. Nobody wants to split a transmission twice. Bookmarked and text-searchable, this copy is yours once bought, kept on the shop laptop for as long as your WA420-3 keeps loading trucks.
What's Inside This Komatsu WA420-3 Manual
| System | Pages | Key Topics |
|---|---|---|
| General | 9-30 | Dimensions and Weights, Specifications, Lubricating and Operating Means |
| Structure and Function | 31-328 | Power Train, Transmission Control, Steering System, Brake System, Air Conditioner |
| Testing and Adjusting | 329-618 | Standard Value Table for Engine, Standard Value Table for Chassis, Standard Value Table for Electrical Parts |
| Disassembly and Assembly | 619-894 | Transmission, Transmission Clutch Pack, Parking Brake |
| Maintenance Standard | 895-946 | Transmission, Transmission Control Valve, Brake |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Tread diameter 6mm torque | 13.2 ± 1.4 Nm | p. 30 |
| Tread diameter 8mm torque | 31.4 ± 2.9 Nm | p. 30 |
| Magnetic clutch switching capacity | 3.5 amps 13 VDC | p. 287 |
| Low pressure switch shut-off pressure | 2.0 bar | p. 287 |
| Turbocharger Torque Value | 45 Nm | p. 639 |
| Turbocharger Exhaust Clamp Torque Value | 8 Nm | p. 639 |
| Backlash between PTO drive gear and drive gear | 0.18 – 0.49 mm | p. 897 |
| Clearance between pump drive shaft and bearing | -0.039 – -0.011 mm | p. 899 |
| Side clearance (SAR(3)-100) | 0.13 – 0.18 mm | p. 929 |
| Clearance between inside diameter of plain bearing and outside of diameter of gear shaft (SAR(3)-100) | 0.06 – 0.149 mm | p. 929 |
| Side clearance (SAR(4)140) | 0.11 – 0.16 mm | p. 931 |
| Side clearance (SAR(1)28) | 0.10 – 0.15 mm | p. 931 |
Komatsu WA420-3 Common Problems This Manual Covers
Komatsu WA420-3 work equipment slow to lift and tilt, main relief valve pressure reading low
Test main relief valve pressure following page 333 with hydraulic oil at 45 to 55°C and the engine at high idle. Read the gauge against 20.58 MPa (210 bar), tolerance +1.0/-0.7 MPa. A low reading means work through the T Mode work equipment checks before you tear into the pump.
Manual Section: Hydraulic and Mechanical System (T Mode) p. 333Hydraulic gear pump worn internally, work equipment pressure still low after relief valve checks out
Remove and disassemble the gear pump, then measure side clearance against the maintenance standard on page 929: 0.13 to 0.18 mm for the SAR(3)-100. Check plain bearing to gear shaft clearance against 0.06 to 0.149 mm and spline shaft rotating torque against 6.9 to 11.8 Nm. Anything out of range means the pump is done.
Manual Section: Maintenance Standard p. 929Transmission will not shift into forward or reverse with the directional lever moved
Measure FORWARD (CNT01) and REVERSE (CNT02) solenoid resistance at the connectors following page 340. Each should read 46 to 58 Ω; check H/L (CNT03) and range (CNT04) solenoids against the same range. Good coils mean you move on to the A Mode directional lever and solenoid signal checks.
Manual Section: Transmission Controller System (A Mode) p. 340Engine overheating with the coolant temperature gauge reading high during heavy loading work
Test the engine water temperature sensor (CNE06) first following page 339, so you know the gauge is telling the truth. Measure approximately 40 Ω at 25°C and approximately 1.7 Ω at 130°C. If the sensor checks good, work through the S Mode overheating troubleshooting before tearing into the cooling system.
Manual Section: Engine System (S Mode) p. 339Parking brake fails to hold the loader on a grade with the switch applied
Measure parking brake disc piston stroke following page 390; a reading past the 9.9 mm maximum is out of limit and the parking brake needs to come apart. Then verify brake accumulator charging pressure against 3.4 ± 0.15 MPa (35 ± 1.5 bar) on page 128 before signing off the brakes.
Manual Section: Brake System p. 390Alternator output voltage low with the engine running at half throttle or above
Measure alternator output voltage with the engine running at half throttle or greater following page 339. The reading must sit between 27.5 and 29.5 V. If it falls short, trace the charging circuit on the wiring diagram before you condemn the alternator.
Manual Section: Testing and Adjusting p. 339Frequently Asked Questions
How do I clear a Komatsu WA420-3 failure code?
To clear a failure code, press the working lamp (rear) switch for at least 2 seconds. Note that failure codes for problems currently occurring (indicated by a flashing display) cannot be cleared. p. 203
What is the torque specification for metric bolts and nuts on the Komatsu WA420-3?
Unless a procedure gives its own value, use the metric torque table on page 30, which sets torque by thread diameter and width across flats. An M8 thread with 13 mm across flats takes 31.4 ± 2.9 Nm (3.2 ± 0.3 kgm). p. 30
How do I reset the travel data display on a Komatsu WA420-3?
To reset from travel data display mode, press the 2nd switch from the top on the left side of the main monitor (the switch below the emergency steering display) and the working lamp (front) switch simultaneously for at least 5 seconds, or start the engine. p. 203
What is the standard valve clearance for the Komatsu WA420-3 engine?
The standard valve clearance for the intake valve is 0.30 mm [0.012 inch] and for the exhaust valve is 0.61 mm [0.024 inch]. These measurements should be taken with the engine cold, below 60°C. p. 354
What is the specified oil capacity for the transmission on the Komatsu WA420-3?
The transmission takes 40 l of oil when you refill it after draining, per the parking brake disassembly procedure on page 711. Run the engine to circulate the oil, then recheck the level. The 60 l figure in the manual is the axle oil quantity, not the transmission. p. 23
Is this Komatsu WA420-3 Shop Manual a digital download?
All 946 pages arrive as one searchable PDF at checkout. Read it at the desk, then take the phone out to the machine.
Can I print a copy of this Komatsu WA420-3 Shop Manual for the shop?
Yes. Print the pages or sections you need for your own shop use. Any standard printer works.
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