Komatsu DWC020_1C_A(S/N 60001-UP (D20A-6))
Komatsubulldozersmall ( - d39)

Komatsu DWC020_1C_A(S/N 60001-UP (D20A-6))

Maintenance schedule, common problems & OEM parts breakdown

The Komatsu D20A-6 (S/N 60001-up) is a compact utility bulldozer in the roughly 3.5-4.2 tonne class, built as the direct-drive narrow-track member of Komatsu's D20/D21-6 small-dozer family. Power comes from a Komatsu 4D95S (4D95S-W-1) mechanical diesel, a 4-cylinder unit of about 2.7 liters displacing around 40 hp (29.8-29.9 kW), driving a dry main-clutch and bevel-gear transmission rather than a powershift unit. Standard operating weight for this configuration is approximately 3,550 kg (7,827 lb); weight shifts somewhat across sibling configurations in the family. The -6 generation ran roughly through the second half of the 1980s into the early 1990s, following the earlier D20A-5 and giving way to the D20A-7 around 1992. Komatsu offered this chassis in multiple configurations sharing the same serial range and shop manual, including angling and low-ground-pressure/swamp blade variants alongside the powershift D21 counterparts built on the same platform.

Across this family, the core split is powertrain: D20-prefix models use Komatsu's direct-drive main-clutch transmission, while D21-prefix models on the same chassis use a powershift transmission, with blade and undercarriage suffixes (A, P, PL, PLL, S, Q, E) layered on top for angling blades, low ground pressure, and swamp duty. The D20A-6 predates any electronic engine or transmission controls, so it has no diagnostic fault codes; every check runs through analog gauges and warning lamps. The follow-on D20A-7 brought engine updates and an optional joystick steering control, marking the shift toward more refined controls in later small dozers. In today's used and parts market, the D20A-6 remains a low-cost, mechanically simple entry point for small land-clearing, acreage, and utility dozer work, valued precisely because it has no electronics to fail and because its parts and service data are shared across the whole A/P/PL/PLL/S/Q/E suffix family from this serial range.

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 DWC020_1C_A(S/N 60001-UP (D20A-6)) specifications

Engine

Engine modelKomatsu 4D95S (4D95S-W-1), naturally aspirated diesel
Cylinders4
Gross power29.8-29.9 kW (40 hp) at 2450 rpm
Displacement2.7 L (164.2 cu in)
Emissions tierNot documented for this serial range - pre-emissions-regulation era machine (mid/late-1980s production)
NotesThe predecessor D20A-5 used a different engine, the 4D94-2N (2.94 L, 39 hp). Parts/shop manuals for S/N 60001-UP confirm the D20/D21-6 range mounts the 4D95S-W-1.

Weights

Operating weight (standard angle-blade configuration)3,550 kg (7,827 lb)
NotesOnly one published configuration found for this serial range; no separate Std/XL/LGP weight split documented for the D20A-6.

Dimensions

Overall length with blade3,400 mm (11 ft 2 in)
Overall length without blade2,550 mm (8 ft 4 in)
Overall width over tracks1,610 mm (5 ft 3 in)
Overall height to cab/canopy top2,475 mm (8 ft 1 in)
Ground clearance295 mm (11.6 in)
Track length on ground1,685 mm (5 ft 6 in)
Track gauge1,310 mm (4 ft 3 in)
Standard track shoe width300 mm (11.8 in)
Track pitch135 mm (5.3 in)

Performance

TransmissionDirect-drive (DD) power train, 3 forward / 2 reverse gears, clutch-brake steering
Travel speed (forward/reverse)Not separately confirmed for this exact serial range. The same-chassis predecessor D20A-5 (identical blade and near-identical operating weight) is rated about 7.4 km/h (4.6 mph) forward and 6.5-6.6 km/h (4.1 mph) reverse across its 3F/2R gears - treat as an approximate reference only and verify with your dealer.
Ground pressureNot separately confirmed for this exact serial range. The D20A-5 predecessor on the same undercarriage is rated about 28.4 kPa (4.1-4.2 psi) - approximate reference only, verify with your dealer.
Drawbar pullNot documented in available factory spec sheets for this serial range - verify with your dealer.
GradeabilityNot documented in available factory spec sheets for this serial range.

Blades

Standard dozer blade width2,170 mm (7 ft 2 in)
Standard dozer blade height590 mm (23.3 in)
Standard blade capacityAbout 0.76 m3 (1.0 cu yd), per the same blade fitted to the predecessor D20A-5
NotesNo alternate blade width/type options (S, SU, A, VPAT) documented for this small-class dozer; it ships with a single 4-way angling blade.

Service capacities

Fuel tank60 L (15.8 gal)
Cooling system13 L (3.5 gal)
Engine oilNot documented for this exact serial range - verify with your dealer or shop manual.
Hydraulic tankNot documented for this exact serial range - verify with your dealer or shop manual.

Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.

DWC020_1C_A(S/N 60001-UP (D20A-6)) fluids & capacities

SystemCapacityRecommended fluid
Engine crankcase (oil pan, with filter)8 L specified (2.1 US gal / 8.5 US qt); 7 L refill on a filter change (1.8 US gal / 7.4 US qt).Engine oil, API classification CD (if only CC is available, halve the change interval). Grade by ambient temperature: SAE10W below about 0°C (32°F), SAE10W-30 across roughly -10 to 20°C (14-68°F), SAE15W-40 across roughly 0 to 30°C+ (32-86°F+), SAE30 above about 10°C (50°F). Below 0°C (32°F) startup, use SAE10W, SAE10W-30 or SAE15W-40 even if daytime temps climb near 10°C (50°F).
Cooling system10 L (2.6 US gal / 10.6 US qt) specified; no separate refill figure listed — treat as the full system fill.Clean water (city water after a detergent flush is acceptable per the OMM's flushing procedure). Add antifreeze once ambient temperature drops below about 0°C (32°F). No branded long-life coolant is named for this serial range.
Fuel tank60 L (15.9 US gal / 63.4 US qt); no refill figure given — fill to the gauge.Diesel fuel per ASTM D975 No. 2 above 0°C (32°F); switch to ASTM D975 No. 1 in colder weather. If fuel sulphur content runs 0.5-1.0%, halve the oil-pan change interval; above 1.0% sulphur, cut it to a quarter.
Main clutch case (D20)6 L specified and 6 L refill (1.6 US gal / 6.3 US qt).Engine oil, SAE10W, used across the full ambient range shown in the OMM chart (roughly -10°C to 30°C+ / 14°F to 86°F+). This machine uses a dry main clutch and mechanical multi-speed transmission, not a powershift unit — the OMM has no separate powershift-transmission fluid line.
Transmission, bevel gear case (D20)16.5 L specified and 16.5 L refill (4.4 US gal / 17.4 US qt).Engine oil. SAE10W below about 10°C (50°F); SAE30 above about 10°C (50°F). On this D20 chassis the transmission and bevel gear (steering) compartment share one combined case and one oil fill — the OMM does not split them into separate reservoirs (that split only applies to the D21 chassis, which uses a separate 'transmission case' plus a 'transfer, bevel gear case').
Final drive case (each side)6 L specified and 6 L refill per side (1.6 US gal / 6.3 US qt each) for the D20A/D21A/D20E/D21E/D20P/D21P-6 group, which covers this A-variant. Sibling blade configurations in the same OMM family spec differently: D20/21PL-6 and D20/21P-6A,6B use 8 L each; D20PLL-6 uses 12 L each — capacity varies by blade/undercarriage configuration, confirm before topping off.Engine oil, same SAE10W (cold) / SAE30 (warm) split as the transmission case.
Hydraulic system / tank33 L specified and 21 L refill (8.7 US gal / 5.5 US gal; 34.9 US qt / 22.2 US qt) for the D20A,21A,E-6 and D20,21P-6A,6B group, which covers this A-variant. The D20,21P,PL,PLL-6 group specs 31 L / 21 L instead — capacity varies by configuration.Engine oil. SAE10W across the widest range (roughly -10°C to 30°C+ / 14°F to 86°F+), SAE10W-30 for roughly -10 to 20°C (14-68°F), or SAE15W-40 for roughly 0 to 30°C+ (32-86°F+).
Pivot shaftNot listed as a separate lubrication point in this OMM.No dedicated pivot-shaft grease spec is published for this serial range in the fuel/coolant/lubricant chart — verify with your dealer if the undercarriage on your unit has a serviceable pivot shaft fitting.
Grease points (angle/tilt cylinder pins, blade control lever pin, track-tension lubricator)Serviced by grease-gun fitting, not a fill capacity. Track-tension grease is pressurized in through a single lubricator and backed off by up to one full turn to loosen — no volume is specified.The OMM calls for greasing the listed fittings (2 points on the angle cylinder bottom pin, 2 on the angle cylinder head pin, 1 each on the tilt cylinder head and bottom pins, 1 on the blade control lever pin, plus the track-tension lubricator) but does not name a specific grease brand or NLGI grade on this OMM's lubricant chart. Use a general-purpose chassis grease unless your dealer specifies otherwise.

Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.

Komatsu DWC020_1C_A(S/N 60001-UP (D20A-6)) maintenance schedule

Service intervalTasks
Every 50 h
  • Check engine oil level before starting and top up as needed
  • Check coolant level and inspect hoses, radiator, and connections for leaks
  • Check fuel level and drain water and sediment from the fuel tank sump
  • Inspect the air cleaner element and dust indicator, clean if restricted
  • Grease track frame, steering linkage, and work equipment pivot points
  • Check track sag and adjust tension if loose
Every 250 h
  • Change engine oil and replace the engine oil filter element
  • Replace the fuel filter cartridge
  • Check battery electrolyte level and clean terminal connections
  • Check and adjust main clutch free play
  • Check steering clutch and brake band linkage adjustment
  • Clean radiator core exterior of dust and debris
Every 500 h
  • Check transmission and bevel gear combined-case oil level, top up with season-correct grade
  • Check final drive case oil level on each side and top up as needed
  • Check hydraulic tank oil level and top up toward refill spec
  • Adjust fan belt tension
  • Inspect and re-torque track shoe bolts
Every 1,000 h
  • Replace transmission and bevel gear combined-case oil
  • Replace final drive case oil on each side
  • Replace the hydraulic tank oil filter element
  • Check and adjust engine valve clearance
  • Replace main clutch case oil
  • Inspect steering clutch and brake band wear, replace if worn past limit
Every 2,000 h
  • Replace hydraulic tank oil
  • Drain, flush, and refill the cooling system
  • Check and adjust fuel injection pump timing
  • Check alternator and starter motor brushes and wiring
  • Replace air cleaner outer and inner elements
  • Inspect undercarriage track links, rollers, and idlers for wear
Every 4,000 h
  • Overhaul the engine top end: cylinder head, injectors, and valve train
  • Reline or rebuild the dry main clutch assembly
  • Rebuild steering clutch and brake assemblies
  • Overhaul final drive gear sets on each side
  • Rebuild or replace undercarriage track chains, rollers, and idlers at wear limits

Servicing the DWC020_1C_A(S/N 60001-UP (D20A-6)) beyond the schedule

Predictive Maintenance & Fluid Analysis

With no engine control unit on the 4D95S(-W-1), there are no fault codes to lean on, so fluid sampling is the main predictive tool. Sample the engine oil pan, the combined transmission-and-bevel-gear case, each final drive, and the hydraulic tank to catch wear metal trends early. The D20 uses one combined transmission/bevel-gear case rather than the split arrangement on D21 siblings, so a single sample there flags both gear-train and main-clutch wear together. Watch the Charge, Oil Pressure, Air Cleaner, Preheat, and Coolant Temp lamps daily as the first line of defense.

Corrective & Common Repairs

Typical corrective work centers on the dry main clutch and steering-clutch/brake system rather than a powershift or hydrostatic drive. Expect main clutch free-play adjustment and eventual relining, steering clutch and brake band wear on turns, and final drive seal leaks on either side. Since this class has no factory PTO winch, aftermarket hydraulic winch retrofits are a common source of added leak points and wiring faults. With no ECU, electrical repairs focus on the analog gauge cluster and its warning-lamp circuits rather than diagnostic scanning.

Overhaul & Rebuild Points

Major rebuild work on the D20A-6 covers the 4D95S(-W-1) engine top end, the dry main clutch, the combined transmission/bevel-gear case, and the final drives on each side. Steering clutch and brake assemblies wear as a set and are usually rebuilt together. Undercarriage overhaul centers on the narrow-track chains, rollers, and idlers rather than any confirmed ripper, counterweight, or forestry-guard hardware, since none of those attachments are documented for this specific serial range. Rebuilds stay focused on core powertrain and undercarriage, not add-on implements.

Seasonal & Environment Servicing

Cold-weather starts on the mechanical 4D95S rely on the glow/preheat lamp and manual warm-up since there is no ECU-assisted cold-start logic. Switch the combined transmission/bevel-gear case to the cold-weather viscosity grade and check the coolant system before winter work. Drain condensation from the 60-liter fuel tank regularly in cold, humid conditions. In hot, dusty acreage or land-clearing environments typical for this compact class, shorten air cleaner element checks and clean the radiator core more often, since the naturally aspirated engine has no turbo margin to absorb heat load.

DWC020_1C_A(S/N 60001-UP (D20A-6)) fault codes & troubleshooting

CodeMeaningLikely causeWhat to do
CHARGE (red pilot lamp)Alternator not charging the battery circuitBroken or slipping fan/alternator belt, worn brushes, faulty regulator, or loose wiring at the alternatorStop and check belt tension and wiring before continuing; test alternator output and battery state of charge
OIL PRESSURE (red pilot lamp)Engine lube oil pressure has dropped below the safe minimumLow oil level, clogged oil filter, worn oil pump, or a failed pressure sender/switchShut the engine down immediately, check oil level and filter condition, then verify pressure with a mechanical gauge before restarting
AIR CLEANER (red pilot lamp)Air intake restriction has reached the clogging threshold on the elementDirty or saturated air filter element, blocked intake ducting, or a faulty restriction switchInspect and clean or replace the air filter element, then confirm the lamp clears after restart
PREHEAT (amber pilot lamp)Intake air preheat (glow) circuit is active for cold startingNormal operation in cold weather; lamp stays on longer than usual if the glow circuit or timer relay is faultyWait for the lamp to go out before cranking; if preheat time is excessive or the lamp never lights, check the glow circuit fuse, relay, and wiring
COOLANT TEMPERATURE (analog gauge, red zone)Engine coolant temperature has risen into the overheat rangeLow coolant level, clogged radiator core or screen, slipping fan belt, faulty thermostat, or a failing water pumpIdle and let temperature drop, then check coolant level, radiator fins, belt, and thermostat once cool; do not remove the radiator cap while hot

Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.

DWC020_1C_A(S/N 60001-UP (D20A-6)) attachments & work tools

Blades

Standard fitment on the A (direct-drive, narrow-track) configuration is a straight/angling dozer blade on trunnion mounts, distinct from the P (power-angle-tilt, wide-track) and S (straight-blade) variants sharing the same parts book. Documented blade width runs roughly 2.19-2.56 m (7.2-8.4 ft) across sources with a blade height near 590 mm (23.3 in); treat the wider figures as belonging to the P/wide-track variant, not this A model. Cat-style S/SU/A/VPAT blade-type naming does not carry over to this Komatsu class - Komatsu differentiates by the model-suffix letter (A/P/S/Q) itself rather than a separate blade-code system.

Rippers

A rear-mounted ripper is cataloged for this chassis, and given the roughly 3.6-4.2 metric ton (7,800-9,300 lb) operating class it is the single-shank pattern rather than the multi-shank parallelogram rippers used on larger Komatsu dozer classes (D40 and up). Shank weight and penetration depth are not documented for this exact serial range - verify with your dealer or the shop manual. The ripper's lift/tilt cylinders share the same work-equipment hydraulic family as the front blade circuit.

Winches

No dedicated factory cable or PTO winch is cataloged for the D20/D21-6 series; factory winch options on Komatsu's dozer line are reserved for larger classes (D65 and up) that carry a rear power take-off. Owners of this class have retrofitted aftermarket hydraulic winches through an auxiliary diverter valve tied into the existing work-equipment circuit, but that is a field modification, not a factory-offered configuration.

Drawbars/counterweights

A rear drawbar/pintle hook is the documented rear-end fitment in place of a ripper on this class, intended for towing rather than ripping duty. No factory counterweight package is documented for this size class; counterweights on Komatsu dozers are generally tied to winch or heavy-ripper installations on larger models, neither of which is standard here.

Cab/ROPS guarding

Standard operator protection is an open ROPS canopy, with a fully enclosed cab offered as an option on this series. Forestry-specific brush/debris screens or belly and rear guarding for forestry/waste duty are not documented for the D20A-6/D21A-6 parts range - packages of that kind are more common on later, larger Komatsu dozer generations. Confirm availability of any forestry guard kit with a dealer before assuming fitment on this vintage/class.

Hydraulic arrangement

Front blade functions (lift, tilt, angle) run off a dedicated multi-spool valve bank as standard, matching the lift/tilt/angle cylinder line-up shown in the parts book. Where fitted, the rear ripper uses its own lift/tilt cylinder pair drawing from the same pump/valve family rather than an independent circuit. No rear auxiliary (winch-type) hydraulic takeoff is factory-plumbed on this class; any rear hydraulic tool has to run through a field-added diverter valve.

All DWC020_1C_A(S/N 60001-UP (D20A-6)) assemblies by section

Every catalogued assembly group for the Komatsu DWC020_1C_A(S/N 60001-UP (D20A-6)). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Guard
Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Guard : Rear Cover And Hydraulic Tank (For Towing Winch)(#60001-63964)
01***20Bolt,(With Auto Emergency Steering)3
01***20Bolt,(For Quick Shift) (Mitsubishi)8
01***25Bolt,(For Canvas Canopy?Head Guard)6
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Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Guard : Rear Cover And Hydraulic Tank (For Towing Winch)(#63965-)
01***20Bolt,(With Auto Emergency Steering)3
01***20Bolt,(For Quick Shift) (Mitsubishi)8
01***40Bolt,(With Service Valve R.H.)4
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Work Equipment
Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Work Equipment : Hitch (For Towing Winch)
01***60Bolt,(Shim Thickness?More Than 8mm)4
01***42Washer,Spring (For Pedal Steering), Washer-Spring4
04***40Pin,Cotter1
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Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Work Equipment : Towing Winch (Brake Band And Linkage)
01***45Bolt, Mounting Bracket To Radiator (Top)1
01***08Nut,(For Canvas Canopy?Head Guard)1
01***36Wahser-Spring, Washer,Spring (Without Towing Winch)1
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Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Work Equipment : Towing Winch (Clutch Shaft And Brake Drum)
01***20Bolt,(With Auto Emergency Steering)4
01***25Bolt,(For Canvas Canopy?Head Guard)4
01***35Bolt,(For Quick Shift) (Mitsubishi)12
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Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Work Equipment : Towing Winch (Fair Lead)
01***20Bolt,(For Quick Shift) (Mitsubishi)8
01***35Bolt, Hydraulic Tank Mounting6
01***30Washer, Spring (Supplied W/Spider Assembly), Washer-Spring8
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Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Work Equipment : Towing Winch (Gear Case)
01***25Bolt,(For Canvas Canopy?Head Guard)12
01***30Bolt,(Not Used With Emergency Str.)25
01***40Bolt (Op)4
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Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Work Equipment : Towing Winch (Logging Arm)
01***20Bolt,(For Quick Shift) (Mitsubishi)6
01***30Bolt,(Not Used With Emergency Str.)2
01***35Bolt, Hydraulic Tank Mounting8
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Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Work Equipment : Towing Winch (P.T.O. Shaft And Pinion Gear)
01***25Bolt,(For Canvas Canopy?Head Guard)15
01***08Nut,(For Canvas Canopy?Head Guard)1
01***30Washer, Spring (Supplied W/Spider Assembly), Washer-Spring15
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Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Work Equipment : Towing Winch (Shift Fork And Cover)
01***30Bolt,(For Mechanical Governor)2
01***20Bolt,(For Quick Shift) (Mitsubishi)4
01***25Bolt,(For Canvas Canopy?Head Guard)11
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Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Work Equipment : Towing Winch (Wire Drum And Gear)
01***30Bolt,(For Quick Shift) (Mitsubishi)4
01***30Bolt,(Not Used With Emergency Str.)23
01***36Wahser-Spring, Washer,Spring (Without Towing Winch)15
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Work Equipment Control System
Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Work Equipment Control System : Work Equipment Control Lever (For Towing Winch)
01***20Bolt,(With Auto Emergency Steering)8
01***40Bolt,(With Air Conditioner)2
01***25Bolt,(For Canvas Canopy?Head Guard)4
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Komatsu : Dwc020_1c_a(S/N 60001-Up (D20a-6)) : Work Equipment Control System : Work Equipment Control Linkage (For Towing Winch)
01***16Bolt (With Air Heater & Conditioner)1
01***35Bolt,(For Position Fixing)1
01***25Bolt,(For Canvas Canopy?Head Guard)2
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DWC020_1C_A(S/N 60001-UP (D20A-6)) serial number reference

On this generation the PIN/serial plate is a small metal tag on the machine frame, typically on the right side of the front frame as seen in the direction of travel; some units carry it inside the cab near the operator's seat. Read it as a plain numeric sequence (for example 60001 and up) - this era of D20/D21-6 dozers did not use the 3-letter alpha prefix scheme found on newer Komatsu machines, so the number itself is the whole identifier. Match the model name suffix (A, P, PL, PLL, S, Q, E) on the nameplate to confirm track width and transmission type, since the serial number alone will not tell you the configuration.

PrefixIdentifies
60001-up (no alpha prefix)D20A-6 direct-drive dozer, narrow-track (A) configuration

Frequently asked questions

What engine powers the Komatsu D20A-6 (S/N 60001-up)?

A Komatsu 4D95S (4D95S-W-1) mechanical diesel: 4 cylinders, about 2.7 liters displacement, rated around 40 hp (29.8-29.9 kW). It has no electronic control unit, so all engine monitoring runs through analog gauges and warning lamps rather than diagnostic fault codes.

What is the operating weight of the D20A-6?

Approximately 3,550 kg (7,827 lb) in standard configuration. Weight varies somewhat across the other blade and undercarriage configurations built on the same D20/D21-6 platform.

What replaced the Komatsu D20A-6?

The D20A-7 succeeded it, arriving around 1992 with engine updates and an optional joystick steering control, continuing the same direct-drive narrow-track D20 line.

What DWC020_1C_A(S/N 60001-UP (D20A-6)) owners discuss

What's the general reputation of the D20A-6's steering-clutch and brake system among owners who've run one for years?
The D20A-6 uses mechanical steering clutches with a hydraulically actuated release, not full hydrostatic steering. Owners who keep the clutch packs adjusted and the brake linkage in spec report the system holds up well for a small utility dozer. The clutch-brake is set to stop the clutch pack in roughly 2.5 to 3.5 seconds after the pedal is depressed; if it runs slower than that, the linkage needs adjustment before the clutch material wears unevenly. Steering-clutch release pressure runs around 1.5 MPa (about 15 kgf/cm2, roughly 213 psi) on this platform, and low pressure there is the first thing to check if one track drags. Because this affects braking and directional control, have your dealer verify clutch-brake timing and release pressure rather than eyeballing it.
One track barely turns the machine in forward but works fine in reverse. Is that a common failure on this dozer, and what causes it?
Yes, this pattern shows up repeatedly in owner reports on the D20 family. When one track drives fine in reverse but its steering lever barely slows or turns the machine going forward, the usual causes are a worn or glazed steering clutch pack, a sticking release piston, or debris blocking the oil strainer that feeds the clutch release circuit. Check the strainer and the hydraulic lines to the steering control valve before assuming the clutch pack itself is shot. This is a directional-control safety item, so have your dealer verify clutch release pressure and pack condition before returning the machine to work.
What undercarriage wear pattern is typical for this size of dozer, and how is track tension kept in spec?
As a compact dozer, the D20A-6 undercarriage generally wears at a moderate pace compared to larger crawler tractors, but units that sat outside for years before resale can show pad and rail corrosion even with usable steel left. Some pads turn up with grouser bars welded on rather than being replaced outright. Track tension is adjusted through a grease zerk on the track frame: pumping grease in tightens the track, and only a small amount makes a noticeable difference, so adjust gradually. Guide-plate-to-track-frame clearance is shim-adjustable; once the rail itself has worn, owners report needing to hold roughly 0.5 mm (0.02 in) per side, since tightening the plates against a worn rail won't fully restore clearance.
Are there known starting quirks with this engine, and is hard starting usually serious?
The D20A-6 runs a small mechanical diesel with a glow-plug preheat circuit rather than an electronically controlled engine, so hard starting is almost always a preheat or fuel-delivery issue, not a control-module fault. Owners typically cycle the glow plugs for about 20 to 30 seconds before cranking and repeat the cycle in cold weather. If the glow-plug indicator on the dash glows normally but the engine still starts hard, weak or partially failed glow plugs are the usual cause at higher hours rather than a wiring fault. Clogged fuel filters or a restricted air intake are the next items to rule out.
What electrical or sensor problems come up most on this machine, and are they usually simple fixes?
This platform predates modern sensor networks, so most electrical complaints trace back to the glow-plug circuit or starter solenoid rather than any sensor fault. A burned-out glow-plug indicator bulb is a common culprit: it interrupts the visible confirmation that current is reaching the glow plugs even when the plugs themselves are fine. Starter and solenoid wiring corrosion is the other frequent complaint, especially on machines that sat outdoors for extended periods before resale. These are generally straightforward continuity checks rather than diagnostic-computer work.
The blade drifts down or moves jerky under load. What's usually behind it?
Blade drift on this dozer is most often traced to the lift or tilt cylinder seals rather than the control valve; worn rod seals or internal cylinder leakage let the blade settle over time. A worn or leaking open-center control valve is the second most common cause, sometimes showing up as oil seeping from the top of the valve housing. Low hydraulic fluid, fluid contamination, or a weakening gear-type hydraulic pump round out the usual suspects. Because blade control affects safe operation near people or structures, have your dealer verify cylinder and valve condition before relying on the blade for grading work.
What should a buyer check before purchasing a used DWC020_1C_A (D20A-6), especially an imported unit?
Check undercarriage condition first: corrosion and worn rails are common on units that sat outside before resale, and welded-on grouser bars can mask pad wear rather than reflect a replacement. Verify the hour meter reading against visible wear evidence, since on older imported machines the meter has sometimes been swapped and no longer reflects true hours. Test steering-clutch behavior in both directions on level ground and confirm the clutch-brake stop feels crisp rather than delayed. Look for oil seepage at the blade cylinders and control valve, and confirm the glow-plug system preheats and the engine starts within a normal cycle. Because clutch, brake, and hydraulic condition all affect safe operation, have your dealer inspect and verify these systems before putting the machine to work.

Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.

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