

The Komatsu Bulldozer D39PX-21 is a robust and versatile piece of heavy machinery designed for various earthmoving tasks. Known for its reliability and efficiency, this bulldozer excels in construction and landscaping applications, making it an essential asset for any industrial operation.
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Tensioning Guide
Belt-diagram
C-120 pulleys
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Pre-built workflows to keep your asset running smoothly.
Daily Electrical System Inspection
Replace Roller and Pulley
Install Engine B-120
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Motion Industries
Applied Industrial Technologies
Electrical Brothers
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Drive Motor
B2 Rollers
Tensioning System
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Komatsu Komatsu Bulldozer D39PX-21 D39PX-21
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1000 Hourly Bulldozer Maintenance
CHANGE OIL IN FINAL DRIVE CASE
WARNING: The oil is at high temperature immediately after the machine has been operated. Wait for the oil to cool down before starting the operation. If there is still pressure remaining inside the case, the oil or plug may fly out. Loosen the plug slowly to release the pressure.
Set the TOP mark at the top, with the UP mark and plug (P) perpendicular to the ground surface.
Set a container under plug (P) to catch the oil.
Remove plugs (P) and (F) with the handle and drain the oil.
Check the O-rings in the plugs for damage. If necessary, replace with new ones.
Tighten plug (P).
Add oil through the hole of plug (F).
When oil begins to overflow from the plug (F) hole, install plug (F).
50 Hourly Bulldozer Maintenance
Warning: Carry out this check before operating the machine.
Prepare a container to catch the fuel that is drained.
Open drain valve (1) at the bottom inside the inspection cover on the left side at the rear of the machine and drain the water and sediment accumulated at the bottom together with fuel.
Warning: When doing this, be careful not to get fuel on yourself.
After clear fuel comes out, close drain valve (1).
250 Hourly Bulldozer Maintenance
LUBRICATING
NOTICE
If dirt or sand is found sticking due to work in the soft ground, carry out greasing every 10 hours of operation.
1. Lower the blde to the ground, then stop the engine.
2. Using a grease pump, pump in grease through the grease fittings shown by arrows.
3. After greasing, wipe off any old grease that was pushed out.
q D39EX,PX
(1) Lift cylinder bottom pin (2 places)
(2) Lift cylinder head pin (2 places)
2000 Hourly Bulldozer Maintenance
Warning: The parts and oil are at high temperature after the engine is stopped, and may cause burns. Wait for the temperature to go down before starting the work.
When removing the oil filler cap, turn it slowly to release the internal pressure, then remove it.
Lower the blade to the ground securely, stop the engine and slowly turn the cap of oil filler (F) to release the internal pressure. Then, remove the cap.
Remove the cover (1) at the bottom of the hydraulic tank.
Place a container to receive drained oil on the track under the drain hole.
Loosen drain valve (2) at lower side of hydraulic tank to drain the oil, then tighten valve (2) again.
For the cab specification machine, cancel lock (3) of the inspection cover at the right side at the rear of the machine, remove the bolts, then remove rear cover (4). Remove the washer tank.
For machines other than the cab specification machines, remove the bolts, then remove the cover at the right side at the rear of the machine and center cover (4) at the rear.
Using the filter wrench, turn filter cartridges (5) and (6) to the left and remove them.
When Required Bulldozer Maintenance
CHECK, CLEAN AND REPLACE AIR CLEANER ELEMENT
Is the yellow piston at the display portion of dust indicator red (7.5 kPa)?
CLEANING OR REPLACING OUTER ELEMENT
Is the yellow piston rises to above 3/5 (5 kPa) of the transparent portion?
Are there small holes or thinner parts found on the element when checked by shining a light through it after cleaning?
CLEAN INSIDE OF COOLING SYSTEM
Is the cooling water inside sub-tank (4) cleaned and filled again with cooling water to a point midway between the FULL and LOW marks?
CHECK TRACK SHOE TENSION, ADJUST
Is the clearance between the bar and the grouser at the midpoint 20 to 30 mm?
Access the parts list for your equipment in MaintainX.
D39Px Power Angle Power Tilt Dozer (Wide Blade) Cutting Edge 21.1kg
12F-70-31261
Engine Oil Filter Cartridge
6733-51-5141
Air Cleaner Element Assembly (Inner And Outer)
600-185-2500
Fuel Filter Cartridge
6732-71-6111
D39Px Power Angle Power Tilt Dozer (Narrow Blade) Cutting Edge 13.0kg
11Y-72-12330
D39Px Power Angle Power Tilt Dozer (Wide Blade) Cutting Edge 21.1kg
12F-70-31261
Engine Oil Filter Cartridge
6733-51-5141
Air Cleaner Element Assembly (Inner And Outer)
600-185-2500
Fuel Filter Cartridge
6732-71-6111
D39Px Power Angle Power Tilt Dozer (Narrow Blade) Cutting Edge 13.0kg
11Y-72-12330
D39Px Power Angle Power Tilt Dozer (Wide Blade) Cutting Edge 21.1kg
12F-70-31261
Engine Oil Filter Cartridge
6733-51-5141
Air Cleaner Element Assembly (Inner And Outer)
600-185-2500
Fuel Filter Cartridge
6732-71-6111
D39Px Power Angle Power Tilt Dozer (Narrow Blade) Cutting Edge 13.0kg
11Y-72-12330
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