Komatsu DNH020_6K_1C(S/N 60001-UP (D20P-6A))
Maintenance schedule, common problems & OEM parts breakdown
The Komatsu D20P-6A (PIN DNH020_6K_1C, S/N 60001-up) is a compact crawler dozer in roughly the 4-metric-ton class, built around the naturally aspirated Komatsu 4D95S-W-1 four-cylinder diesel rated near 29.8 kW (40 HP) at 2450 rpm. Operating weight for this wide-track, power-angle-tilt (PAT) configuration runs about 3,940 kg (8,686 lb); other suffix variants in the same serial block run lighter or heavier depending on track width and blade type. This machine belongs to Komatsu's -6 generation, produced roughly 1985-1992, sitting between the earlier -5 generation and the later -7 generation that followed it. The D20/D21-6 family was sold in numerous configurations off one shared parts and shop manual: D20 denotes direct-drive transmission (as fitted here) versus D21 powershift, A denotes narrow-track angle-blade, P denotes wide-track power-angle-tilt (this unit), PL/PLL adds a longer track frame, S is a straight-blade version, and Q adds a factory ripper option.
Across the D20/D21-6 lineup, the core difference between suffixes is blade geometry and track gauge rather than engine or major powertrain changes; every variant in this S/N 60001-up block shares the same 4D95S-W-1 engine and direct-drive or powershift transmission architecture, with capacity and lubrication points split only by suffix bracket. Compared with the later -7 and -8 generations, this -6 series still uses dry (non-oil-bathed) steering clutches and brakes and a fiberglass rain canopy as standard cab protection rather than a standard ROPS-certified steel canopy, which only became standard on the later -8 generation. In the used and parts market today, this class of small Komatsu dozer remains in demand for tight-access grading, trail, and small-lot dozing work where a full-size dozer is overkill, and because so many suffix variants share one factory manual and parts book, sourcing filters, seals, and undercarriage parts across the family is comparatively straightforward even decades after production ended.
Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.
Komatsu DNH020_6K_1C(S/N 60001-UP (D20P-6A)) specifications
Engine
| Engine model | Komatsu 4D95S (4D95S-W-1), naturally aspirated diesel, 4 cylinders |
| Gross power | 29.8 kW (40 HP) at 2450 rpm |
| Displacement | 2.69 L (164.2 cu in) |
| Emissions tier | Pre-emissions era design (mid-1980s mechanical diesel); no EPA/EU tier certification published |
| Notes | D20 (direct-drive) and D21 (powershift) Series-6 machines share the same 4D95S-W-1 base engine per factory documentation; net power not published for this configuration |
Weights
| Operating weight (D20P-6A, wide-track P config) | approx. 3,940 kg (8,686 lb) |
| Notes | No separate XL or LGP weight variant published; P designation itself denotes the wide-track, power-angle-tilt configuration |
Dimensions
| Overall length with blade | 3.41 m (11.2 ft) |
| Overall length without blade | 2.56 m (8.4 ft) |
| Overall width over tracks | 2.56 m (8.4 ft) |
| Overall height to cab/canopy top | 2.53 m (8.3 ft) |
| Ground clearance | 0.37 m (1.2 ft) |
| Track length on ground | 1.69 m (5.55 ft) |
| Track gauge (centerline to centerline) | 1.49 m (4.9 ft) |
| Standard shoe width | 510 mm (20.1 in) |
| Track pitch | 135 mm (5.32 in) |
| Blade width | 2.56 m (8.4 ft), angling to about 2.44 m (8 ft) |
| Blade height | 590 mm (23.3 in) |
Performance
| Ground pressure | Not documented for this exact serial range in available factory or dealer literature — verify with your dealer |
| Travel speed forward/reverse | Not documented for this exact serial range in available factory or dealer literature — verify with your dealer |
| Drawbar pull | Not documented for this exact serial range in available factory or dealer literature — verify with your dealer |
| Gradeability | Not documented for this exact serial range in available factory or dealer literature — verify with your dealer |
| Transmission | Direct-drive (DD) type, 3 forward and 2 reverse gears, per the factory spec sheet for the D20 line |
Blades
| Standard P-type blade (power angle-tilt, wide track) | Width approx. 2.56 m (8.4 ft), height 590 mm (23.3 in); capacity not published |
| Notes | Blade capacity in cubic volume is not published for this model in available sources |
Service capacities summary
| Fuel tank capacity | Not documented for this exact serial range in available factory or dealer literature — verify with your dealer |
| Hydraulic system capacity | Not documented for this exact serial range in available factory or dealer literature — verify with your dealer |
| Engine oil capacity | Not documented for this exact serial range in available factory or dealer literature — verify with your dealer |
| Cooling system capacity | Not documented for this exact serial range in available factory or dealer literature — verify with your dealer |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
DNH020_6K_1C(S/N 60001-UP (D20P-6A)) fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Engine crankcase (oil pan, with filter) | 8 L specified, 7 L refill (2.1 US gal specified, 1.8 US gal refill) | Komatsu engine oil, API classification CD (API CC acceptable but halves the normal oil-change interval). Viscosity by ambient temperature: SAE10W below about 10°C (50°F); SAE30 above about 10°C (50°F); SAE10W-30 or SAE15W-40 multigrade cover most of the range from about -10°C to 30°C+ (14°F to 86°F+). Below 0°C (32°F) start-up, use SAE10W, SAE10W-30, or SAE15W-40 even if daytime temperature rises. |
| Cooling system (radiator + block) | 10 L specified (2.6 US gal). No listed refill figure (topped up as needed). | Water with antifreeze added for cold-climate operation. No coolant type/concentration spelled out beyond "add antifreeze" for temperatures below about 0°C (32°F). |
| Fuel tank | 60 L specified (15.9 US gal). No refill figure listed (fuel is not a periodic-service refill item). | Diesel fuel meeting ASTM D975 No.2 for normal ambient temperatures (roughly 0°C/32°F and up). ASTM D975 No.1 diesel for very cold conditions below about -10°C (14°F). |
| Main clutch case (D20-series compartment) | 6 L specified and refill (1.6 US gal). | Same Komatsu engine oil as the crankcase. Single SAE10W grade is specified across the full ambient range shown on the chart — no seasonal split for this compartment. |
| Transmission, bevel gear case (combined, D20-series) | 16.5 L specified and refill (4.4 US gal). The transmission and bevel gear case share one combined reservoir on this direct-drive configuration. | Komatsu engine oil. SAE10W below about 10°C (50°F); SAE30 above about 10°C (50°F). |
| Final drive case (each side) | 8 L specified and refill per side (2.1 US gal), per side. | Komatsu engine oil, same SAE10W (below ~10°C/50°F) / SAE30 (above ~10°C/50°F) split as the transmission/bevel gear case. |
| Hydraulic system/tank | 33 L specified, 21 L refill (8.7 US gal specified, 5.5 US gal refill). | Komatsu engine oil (this era of small dozer uses engine oil in the hydraulic tank, not a dedicated hydraulic fluid). SAE10W at the cold end, SAE10W-30 or SAE15W-40 multigrade across most of the range, similar temperature bands to the engine crankcase. |
| Pivot shaft | Not listed as a separate reservoir in this machine's fuel/coolant/lubricant chart. | Not documented for this specific serial range — verify with your dealer if the machine has a track-frame pivot lubrication point outside the listed reservoirs. |
| Grease points | No single reservoir capacity; grease-gun points only. On hydraulic angle-tilt and hydraulic tilt dozer blade variants, 250-hour service calls for lubricating the angle cylinder bottom pin and head pin (2 points each), tilt cylinder head and bottom pins (1 point each), lift cylinder head and bottom pins and rod pin (2 points each), angle-tilt frame center pin (1 point) and support pin (2 points), lift cylinder yoke (multiple points), tilt brace pin (2 points), and center brace pin (4 points). | Manual instructs to "apply grease to grease fittings" without naming a specific grease brand or NLGI grade — standard multipurpose chassis grease applies per normal Komatsu practice, but no exact spec is printed in this OMM. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Komatsu DNH020_6K_1C(S/N 60001-UP (D20P-6A)) maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 50 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
| Every 4,000 h |
|
Servicing the DNH020_6K_1C(S/N 60001-UP (D20P-6A)) beyond the schedule
Predictive Maintenance & Fluid Analysis
Sample engine oil, transmission/bevel gear case oil, and final drive oil at each 500/1000-hour change to catch early wear in the 4D95S-W-1 engine and direct-drive powertrain before it shows up as surge or slipping. Because this configuration runs engine-oil-spec fluid in the hydraulic tank rather than dedicated hydraulic oil, watch for cross-contamination readings between hydraulic and engine samples. Track coolant condition closely since this generation lacks any electronic monitoring, so lab results are the only early warning for pump or liner wear.
Corrective & Common Repairs
Most field complaints on this unit trace to the dry steering clutches and brakes grabbing or slipping unevenly after idle periods, and to lift-cylinder seal leak-down that lets the PAT blade settle overnight. Check the transmission hydraulic fluid and shift linkage first on hard-shifting complaints, since low or dirty fluid feeding the clutch-pack apply pressure is the more common cause than a worn clutch pack itself. Injector wear and clogged air cleaners are the leading causes of rpm surge and smoke.
Overhaul & Rebuild Points
Plan undercarriage rebuild around sprocket tooth profile (pointed teeth mean past the wear limit) and even side-to-side roller wear rather than a fixed hour number, since this lighter-duty class wears faster than larger dozers under the same abuse. Steering clutch and brake friction packs are the other major rebuild item on this direct-drive machine; glazed plates or a brake band that won't hold adjustment call for a full clutch housing teardown rather than another field adjustment.
Seasonal & Environment Servicing
Switch engine, main clutch case, transmission/bevel gear case, final drive, and hydraulic-tank fluids to the SAE10W cold-weather grade below about 10°C (50°F) per the factory chart, and add antifreeze to the cooling system before temperatures drop near 0°C (32°F). In dusty conditions, check the air cleaner element more often than the standard interval, since this naturally aspirated engine has no turbo margin to mask intake restriction. Rodent nesting in the air intake is a known issue on machines stored outdoors between seasons.
DNH020_6K_1C(S/N 60001-UP (D20P-6A)) common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| 103-60-23240 | Cartridge,Hydraulic Oil Filter | Hydraulic service | Check fitment → |
| 113-60-43320 | Cartridge,Hydraulic Oil Filter (D31s) | Hydraulic service | Check fitment → |
| 113-60-43321 | Cartridge,Hydraulic Oil Filter (D31s) | Hydraulic service | Check fitment → |
| 07002-03334 | O-Ring, At Transmission Filter | Scheduled service item | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
DNH020_6K_1C(S/N 60001-UP (D20P-6A)) fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| CHARGE lamp (red) | Alternator/charging circuit warning lamp lit with engine running | Alternator belt slipping or broken, faulty alternator, loose or corroded battery/charging wiring | Stop engine, check fan/alternator belt tension and wiring connections before restarting |
| Engine oil pressure lamp (red) | Engine lubrication oil pressure below safe minimum | Low engine oil level, clogged oil filter, worn oil pump or bearings, oil pressure switch failure | Shut engine down immediately, check oil level and filter condition before restart |
| Coolant temperature warning lamp (red) | Engine coolant temperature above normal operating range | Low coolant level, clogged radiator fins, slipping or broken fan belt, faulty thermostat | Idle engine to cool, check coolant level and radiator/fan belt once safe to open hood |
| Air cleaner restriction indicator | Air filter element clogged, restricting intake airflow | Dust/debris buildup in air cleaner element from operating in dirty conditions | Service or replace the air cleaner element and reset the indicator |
| Glow plug / preheat indicator lamp | Shows when intake air preheating is active for cold starting | Normal cold-start function; lamp staying on after warm-up points to a stuck preheat circuit or faulty glow plug relay | Wait for lamp to go out before cranking; if it never goes out, have the preheat circuit checked |
| Fuel level / fuel filter warning | Low fuel level or, on some panels, water/sediment buildup noted at the fuel filter sediment bowl | Fuel running low, or water and sediment collected in the fuel filter/strainer | Refuel as needed and drain the fuel filter sediment bowl at scheduled intervals |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
DNH020_6K_1C(S/N 60001-UP (D20P-6A)) attachments & work tools
Blades
This serial run splits into two blade variants: the base D20P-6 is a Straight Tiltdozer, while the D20P-6A covered here is the Power Angle Tilt (PAT) version, using lift, tilt, and angle cylinders plus an angle selector valve so the blade can angle to either side as well as tilt. Blade width runs about 2.56 m (8.4 ft) with a blade height near 590 mm (23.3 in), consistent across spec databases. This small dozer class does not offer a semi-U or U-blade, and full VPAT (variable-angle) blades are a feature of much larger Komatsu dozer classes, not this one; published cutting/capacity ratings for this blade size were not found and should be confirmed with a dealer.
Rippers
A rear ripper/scarifier attachment was catalogued by Komatsu for this D20/D21-6 size class, but it is a single-shank scarifier type only — multi-shank parallelogram rippers start on much larger Komatsu dozer classes and are not offered here. Factory-fitted rippers on machines this size are uncommon in the field even though listed in the parts book; shank weight and penetration depth are not documented for this compact class and should be verified against the specific parts book for this serial range.
Winches
No winch is a factory-cataloged option for this D20/D21-6 series. Where a winch is fitted, it is an aftermarket hydraulic unit tapped into the existing blade tilt or angle circuit through an added diverter valve, sized to a light-duty class matching this machine's roughly 3.9-4.1 t operating weight. Sharing a circuit this way commonly disables blade tilt/angle while the winch is in use unless an extra control-valve section is added.
Drawbars/counterweights
No published factory drawbar or counterweight package was found for this size class; rear-end fitment on the D20/D21-6 line is centered on the optional ripper/scarifier rather than a dedicated drawbar or counterweight assembly of the kind offered on larger Komatsu dozer families. Treat any drawbar or counterweight need as a dealer-fabricated or aftermarket solution for this model.
Cab/ROPS guarding
Standard cab protection on this series was a fiberglass rain canopy; a ROPS-certified steel canopy or a lighter, non-certified utility canopy are documented aftermarket/dealer replacements for it, with a heavier-duty steel utility canopy and rear screen available for extra brush/debris protection. ROPS canopy only became standard equipment on the later -8 generation, implying it remained optional on this -6 machine. No factory forestry-specific guarding package (screened glass, belly guards, radiator screens) is documented for this small class; such packages are more typical of larger Komatsu forestry dozer models.
Hydraulic arrangement
The front blade circuit runs off the main hydraulic control valve through lift and tilt cylinders on the base Straight Tilt version, with an added angle cylinder and angle selector valve on this D20P-6A Power Angle Tilt version. There is no separate standard rear circuit for a ripper or winch on this class; any rear-mounted ripper cylinder or aftermarket winch must share the existing blade valve bank via a diverter, since a dedicated extra valve section is not standard equipment on this model.
All DNH020_6K_1C(S/N 60001-UP (D20P-6A)) assemblies by section
Every catalogued assembly group for the Komatsu DNH020_6K_1C(S/N 60001-UP (D20P-6A)). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Guard
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Guard : Rear Cover And Hydraulic Tank (For 3-Point Hitch)(#60001-63996)
| 01***20 | Bolt,(With Auto Emergency Steering) | 3 |
| 01***20 | Bolt,(For Quick Shift) (Mitsubishi) | 8 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 6 |
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Guard : Rear Cover And Hydraulic Tank (For 3-Point Hitch)(#63997-)
| 01***20 | Bolt,(With Auto Emergency Steering) | 3 |
| 01***20 | Bolt,(For Quick Shift) (Mitsubishi) | 8 |
| 01***40 | Bolt,(With Service Valve R.H.) | 4 |
Work Equipment
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Work Equipment : 3-Point Hitch (1/2)
| 01***45 | Bolt, Mount Center Hinge Retainer (Lower) | 4 |
| 01***20 | Bolt,(For Quick Shift) (Mitsubishi) | 6 |
| 01***40 | Bolt (Op) | 8 |
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Work Equipment : 3-Point Hitch (2/2)
| 01***16 | Bolt, Mount Washer Tank To Bracket, Bolt | 2 |
| 01***25 | Bolt,Without Revolution Sensor | 6 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 4 |
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Work Equipment : 3-Point Hitch Cylinder
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 2 |
| 01***32 | Washer,(With Auto Emergency Steering) | 2 |
| 07***70 | O-Ring,(For Intake Air Cover) | 1 |
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Work Equipment : Swing Drawber (For 3-Point Hitch)
| 01***35 | Bolt,R.H. Outside And L.H. Inside | 8 |
| 01***40 | Bolt,R.H. Outside And L.H. Inside, Bolt | 4 |
| 01***42 | Washer,Spring (For Pedal Steering), Washer-Spring | 12 |
Work Equipment Control System
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Work Equipment Control System : Hydraulic Piping (3-Point Hitch Cylinder Line)(For 3-Point Hitch)
| 01***18 | Bolt | 1 |
| 01***20 | Bolt,(With Auto Emergency Steering) | 1 |
| 01***20 | Bolt,(For Quick Shift) (Mitsubishi) | 2 |
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Work Equipment Control System : Hydraulic Tank And Filter (For 3-Point Hitch)
| 01***25 | Bolt,Without Revolution Sensor | 7 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 3 |
| 01***25 | Washer,Spring?For Additional Rear Lam | 7 |
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Work Equipment Control System : P.T.O. Control Lever (For 3-Point Hitch)
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 2 |
| 01***16 | Bolt, Battery To Frame Ground Wire Attaching | 2 |
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 2 |
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Work Equipment Control System : Work Equipment Control Lever (1/2) (For 3-Point Hitch)
| 01***16 | Bolt (With Air Heater & Conditioner) | 2 |
| 01***20 | Bolt,(With Auto Emergency Steering) | 8 |
| 01***30 | Bolt,(For Mechanical Governor) | 1 |
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Work Equipment Control System : Work Equipment Control Lever (2/2) (For 3-Point Hitch)
| 01***05 | Nut,L.H. Thread (D31s) | 2 |
| 01***05 | Nut,L.H. (For Trimming Dozer) | 2 |
| 01***06 | Nut,(With Back-Up Alarm) (Op), Nut; Was 01580-10806 | 2 |
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Work Equipment Control System : Work Equipment Valve (1/3) (For 3-Point Hitch)
| 01***16 | Bolt (Op) | 4 |
| 01***25 | Bolt, Seal Cover Mounting | 2 |
| 01***30 | Bolt | 2 |
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Work Equipment Control System : Work Equipment Valve (2/3) (For 3-Point Hitch)
| 01***16 | Bolt (Op) | 4 |
| 01***25 | Bolt, Seal Cover Mounting | 2 |
| 01***30 | Bolt | 2 |
Komatsu : Dnh020_6k_1c(S/N 60001-Up (D20p-6a)) : Work Equipment Control System : Work Equipment Valve (3/3) (For 3-Point Hitch)
| 01***08 | Nut (Op) | 1 |
| 07***11 | O-Ring (Kit) | 1 |
| 07***15 | O-Ring,(Without Boom Kickout) | 1 |
Frequently asked questions
What engine does the Komatsu D20P-6A (DNH020_6K_1C) use?
It uses the naturally aspirated Komatsu 4D95S-W-1 four-cylinder diesel, displacing about 2.69 L (164.2 cu in) and rated near 29.8 kW (40 HP) at 2450 rpm. This same base engine is shared across the D20 and D21 suffix variants in the S/N 60001-up serial block.
What is the operating weight of this configuration?
The D20P-6A wide-track, power-angle-tilt configuration weighs approximately 3,940 kg (8,686 lb). Other suffix variants in the same family (narrower-track A models, longer-track PL/PLL models) run lighter or heavier, so treat weight as varying by configuration.
What replaced the Komatsu D20P-6A in Komatsu's dozer lineup?
It was succeeded by the D20/D21-7 generation, produced roughly 1992-2000, and later by the D20/D21-8 generation from 2000 onward, which introduced a standard ROPS-certified steel canopy in place of this generation's standard fiberglass canopy.
What DNH020_6K_1C(S/N 60001-UP (D20P-6A)) owners discuss
What's a known quirk of the steering clutches and brakes on this dozer?
How does the powertrain (transmission) tend to behave, and what causes shifting trouble?
What undercarriage wear patterns should owners expect, and how do people judge remaining life?
What engine quirks come up for this dozer's diesel engine?
What electrical or charging issues show up most often?
Do owners report any hydraulic issues with the blade circuit?
What should a buyer check before purchasing a used example of this dozer?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
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