Komatsu 4D95S-W-1F-A(S/N 23318-UP)
Maintenance schedule, common problems & OEM parts breakdown
The Komatsu 4D95S-W-1F-A is a four-cylinder, water-cooled, direct-injection diesel engine used in the D20 and D21 series crawler dozers (6th generation). It powers machines in the 15-20 ton operating weight class, with production spanning approximately 1998 to 2003. This engine succeeded the mechanical 4D95S-1 and was later replaced by the electronically controlled SAA4D95LE-6 in the 7th generation D21A-7 series. Configurations included standard and long-track (LGP) undercarriages for varied ground pressure requirements.
The 4D95S-W-1F-A represents the transition to Tier 2/Stage II emissions compliance, introducing electronic fuel control while retaining mechanical robustness. It matters in the used market because its simple architecture and high torque output make it a preferred swap for older GD85A/GD105A dozers and industrial applications. The engine's availability in the aftermarket for rebuild kits and its compatibility with common Komatsu hydraulic systems ensure long-term parts support.
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 4D95S-W-1F-A(S/N 23318-UP) specifications
Engine
| Model | 4D95S-W-1F-A |
| Series | 95 Series |
| Cylinders | 4 |
| Displacement | 3.26 L (198.9 cu in) |
| Bore | 95 mm (3.74 in) |
| Stroke | 115 mm (4.53 in) |
| Gross Power | varies by configuration/series |
| Net Power | varies by configuration/series |
| Emissions Tier | Tier 4 Interim / Stage IIIB |
Weights
| Operating Weight | not documented for this exact serial range — verify with your dealer |
| Shipping Weight | not documented for this exact serial range — verify with your dealer |
| Ground Pressure | not documented for this exact serial range — verify with your dealer |
Dimensions
| Transport Length | not documented for this exact serial range — verify with your dealer |
| Transport Width | not documented for this exact serial range — verify with your dealer |
| Transport Height | not documented for this exact serial range — verify with your dealer |
| Track Gauge | not documented for this exact serial range — verify with your dealer |
| Ground Clearance | not documented for this exact serial range — verify with your dealer |
Performance
| Travel Speed | not documented for this exact serial range — verify with your dealer |
| Gradeability | not documented for this exact serial range — verify with your dealer |
Service capacities (summary)
| Engine Oil | not documented for this exact serial range — verify with your dealer |
| Cooling System | not documented for this exact serial range — verify with your dealer |
| Fuel Tank | not documented for this exact serial range — verify with your dealer |
| Hydraulic System | not documented for this exact serial range — verify with your dealer |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
Komatsu 4D95S-W-1F-A(S/N 23318-UP) maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
Servicing the 4D95S-W-1F-A(S/N 23318-UP) beyond the schedule
Predictive Maintenance & Fluid Analysis
Monitor KOWA oil samples at every 500-hour interval to detect wear metals from the 4D95S-W-1F-A's piston rings and cylinder liners. Check coolant SCA concentration to prevent cavitation in the wet sleeve liners. Inspect the fuel water separator daily to protect the high-pressure injection pump. Track hydraulic oil particle count to safeguard the dozer's blade and ripper control valves. Use Komatsu EO or equivalent heavy-duty diesel oil to manage soot load from the direct injection system.
Corrective & Common Repairs
Address head gasket failures by checking cylinder head warpage and bolt torque sequence. Replace worn piston rings if compression drops below spec, noting the 4D95S-W-1F-A uses specific piston heights. Inspect the fuel injection pump for leakage around the shaft seal. Check the turbocharger shaft play and bearing clearance. Replace the water pump if coolant circulation fails, as the 4D95S-W-1F-A relies on a mechanical pump for cooling. Verify the starter motor engagement for reliable cold starts.
Overhaul & Rebuild Points
Perform an in-frame overhaul when cylinder liner wear exceeds limits or piston scoring occurs. Replace main and rod bearings if oil pressure drops significantly. Inspect the crankshaft for journal wear and taper. Recondition the cylinder head, resurfacing the deck and replacing valve guides and seats. Install new cylinder liners if the bore is out of specification. Use a complete gasket kit to ensure proper sealing of the head, oil pan, and turbocharger connections.
Seasonal & Environment Servicing
In cold weather, use low-viscosity engine oil and ensure the coolant mixture provides adequate freeze protection. Check the battery charge level frequently as cold temperatures reduce cranking power. In dusty environments, clean the air filter more often and inspect the intake manifold for debris. In high-temperature conditions, clean the radiator and oil cooler fins daily to prevent overheating. Verify the fan belt tension to ensure proper cooling fan operation in extreme heat.
4D95S-W-1F-A(S/N 23318-UP) common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| 07281-00197 | Clamp,(With Pre-Fuel Filter) | Fuel system service | Check fitment → |
| 600-311-1190 | Plate? Caution,Fuel Filter | Fuel system service | Check fitment → |
| 600-311-6220 | Cartridge,Fuel Filter | Fuel system service | Check fitment → |
| 600-311-9600 | Fuel Filter Ass'Y | Fuel system service | Check fitment → |
| 600-311-7440 | Cartridge,Fuel Filter | Fuel system service | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
4D95S-W-1F-A(S/N 23318-UP) fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| CA115 | Engine crankshaft speed sensor failure | Broken sensor, wiring issue, or connector corrosion | Replace the speed sensor and verify voltage at the pin connector |
| CA441 | Battery voltage too low | Weak battery or charging system failure | Replace the battery or alternator and check the voltage regulator |
| CA442 | Battery voltage too high | Faulty voltage regulator or alternator | Replace the alternator or battery and check the voltage regulator |
| AA10NX | Air cleaner clogging | Dirty or blocked air filter element | Replace the air filter |
| CA122 | Intake air pressure high voltage | Intake pressure sensor malfunction or wiring issue | Verify the intake pressure sensor and wiring |
| CA123 | Intake air pressure low voltage | Sensor short or airflow restriction | Check for a sensor short or an airflow restriction |
| CA153 | Intake air temperature sensor error (High) | Faulty IAT sensor | Replace or test the IAT sensor |
| CA154 | Intake air temperature sensor error (Low) | Faulty IAT sensor | Replace or test the IAT sensor |
| CA428 | Fuel moisture sensor invalid voltage (High) | Contaminated fuel or sensor harness issue | Ensure a clean fuel supply and check the moisture sensor harness |
| CA429 | Fuel moisture sensor invalid voltage (Low) | Contaminated fuel or sensor harness issue | Ensure a clean fuel supply and check the moisture sensor harness |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
4D95S-W-1F-A(S/N 23318-UP) attachments & work tools
Bulldozer Blade Configurations
The Komatsu D20 and D21 series machines powered by the 4D95S-W-1F-A engine utilize semi-universal (SU) and straight (S) blade configurations. Factory specifications for these models typically include blade widths ranging from 2.5 to 3.0 meters (8.2 to 9.8 feet) and capacities between 1.5 and 2.0 cubic meters (2.0 to 2.6 cubic yards). Guarding options often include side cutters and corner guards to extend blade life during heavy dozing operations.
Ripper Attachments
Single-shank and multi-shank ripper options are available for the D20 and D21 dozer platforms. Ripper shank lengths typically range from 1.0 to 1.5 meters (3.3 to 4.9 feet) depending on the specific machine frame and hydraulic system capacity. Mounting systems utilize direct-frame hydraulic cylinders with quick-attach pins for depth adjustment and transport positioning.
Hydraulic System Compatibility
Work tools requiring hydraulic power must interface with the machine's main control valve and auxiliary circuits. Standard hydraulic flow rates for this engine class typically range from 100 to 150 liters per minute (26 to 40 gallons per minute) at rated engine speed. High-flow options may be available for specialized attachments, requiring verification of the specific machine's hydraulic kit configuration.
Undercarriage and Track Configurations
The D20 and D21 dozers are equipped with crawler undercarriages designed for stability and traction. Track shoe widths typically range from 400 to 600 millimeters (16 to 24 inches) to suit varying ground conditions. Ground pressure and flotation characteristics are optimized for the machine's operating weight class, with options for LGP (Low Ground Pressure) configurations in soft terrain applications.
All 4D95S-W-1F-A(S/N 23318-UP) assemblies by section
Every catalogued assembly group for the Komatsu 4D95S-W-1F-A(S/N 23318-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Cooling System
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cooling System : Water Pump And Cooling Fan
| 01***16 | Screw | 5 |
| 01***20 | Screw | 2 |
| 01***25 | Bolt,(With Corrosion Resistor) | 6 |
Cylinder Block
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Block : Camshaft And Tappet
| 01***20 | Screw | 2 |
| 04***16 | Fitting Wedge | 1 |
| 62***31 | Thrust Washer | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Block : Crankshaft
| 61***20 | Bolt | 1 |
| 62***00 | Crankshaft Ass'Y | 1 |
| 62***00 | Main Metal Ass'Y | 5 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Block : Cylinder Block
| 01***55 | Bolt, Mount Tube To Switch Pump | 8 |
| 01***16 | Screw | 1 |
| 01***20 | Screw | 2 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Block : Flywheel And Flywheel Housing
| 01***30 | Bolt | 6 |
| 01***30 | Bolt - Lower Oil Cooler Outlet Tubemounting | 11 |
| 01***40 | Bolt,(Shim 3-Piece) | 3 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Block : Front Cover And Gear
| 01***10 | Bolt | 1 |
| 01***70 | Bolt,(For 75a Alternator) | 1 |
| 01***16 | Bolt | 2 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Block : Oil Pan (Double Bottom Type)(#36389-74638)
| 01***16 | Bolt, Mount Solenoid Valve | 24 |
| 01***16 | Screw | 24 |
| 07***12 | Washer, Gasket,(Without Thermo Sensor) (K1) | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Block : Oil Pan (Double Bottom Type)(#74639-)
| 01***20 | Bolt,(Forwarded Individually Parts) | 24 |
| 07***12 | Washer, Gasket,(Without Thermo Sensor) (K1) | 1 |
| 07***16 | Gasket,(For Pc750-6) (See Fig.A2110) | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Block : Oil Pan(#23318-74638)
| 01***16 | Bolt, Mount Solenoid Valve | 24 |
| 01***16 | Screw | 24 |
| 07***16 | Gasket,(For Pc750-6) (See Fig.A2110) | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Block : Oil Pan(#74639-)
| 01***20 | Bolt,(Forwarded Individually Parts) | 24 |
| 07***16 | Gasket,(For Pc750-6) (See Fig.A2110) | 1 |
| 62***12 | Pan,Oil | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Block : Piston And Connecting Rod
| 04***12 | Ring, Snap | 8 |
| 62***40 | Piston (S) | 4 |
| 62***00 | Piston Ring Ass'Y,Per Cylinder | 4 |
Cylinder Head
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Head : Air Cleaner And Mounting
| 01***30 | Bolt,(Water Separator Spec.) | 1 |
| 01***16 | Bolt,(With Alternator Cover Type) | 2 |
| 01***06 | Nut | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Head : Air Intake Manifold And Connection(#23318-30907)
| 01***65 | Stud | 1 |
| 01***65 | Bolt,(With Water Separator) | 3 |
| 01***75 | Bolt,(For Shipping) | 8 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Head : Air Intake Manifold And Connection(#30908-)
| 01***65 | Stud | 1 |
| 01***12 | Bolt,(With Speedometer) | 4 |
| 01***65 | Bolt,(With Water Separator) | 3 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Head : Cylinder Head
| 01***20 | Bolt, Hose Clamps (Inlet And Return Line Hoses) | 4 |
| 01***32 | Washer,(Not Used With Emergency Str.) | 17 |
| 02***04 | Plug, Pipe | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Head : Cylinder Head Cover
| 61***10 | Cap, Oil Filler | 1 |
| 61***20 | Screw | 3 |
| 61***30 | Washer,(B) | 3 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Head : Exhaust Manifold And Muffler
| 01***25 | Grub Screw | 4 |
| 01***45 | Bolt, Bracket Mounting | 8 |
| 01***11 | Nut (M14-1.50 Thd), Nut; Was 01582-01411 | 2 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Head : Exhaust Manifold And Muffler (With Spark Arrester)
| 01***25 | Grub Screw | 4 |
| 01***45 | Bolt, Bracket Mounting | 8 |
| 01***11 | Nut (M14-1.50 Thd), Nut; Was 01582-01411 | 2 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Cylinder Head : Rocker Arm
| 01***12 | Bolt,(Without R.P.C.U.) | 1 |
| 01***65 | Bolt,(For Alternator Bracket Mount) | 5 |
| 61***30 | Nut | 8 |
Electrical System
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Electrical System : Alternator (15a)
| 60***60 | Alternator A. (15a) | 1 |
| KD***70 | Cover | 1 |
| KD***30 | Retainer | 2 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Electrical System : Alternator (25a)
| 60***10 | Alternator A. (25a) | 1 |
| KD***57 | Bearing,Ball? Front | 1 |
| KD***11 | Rear Bracket Ass'Y | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Electrical System : Alternator And Mounting (15a)
| 01***25 | Bolt,(With Corrosion Resistor) | 1 |
| 01***45 | Bolt | 1 |
| 01***06 | Nut | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Electrical System : Alternator And Mounting (25a)
| 01***55 | Bolt,(With Engine Stop Motor Type) | 1 |
| 01***30 | Bolt | 1 |
| 01***11 | Nut,(For Center Guard) | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Electrical System : Starting Motor (2.8kw)
| 60***70 | Starting Motor Ass'Y,(2.8kw) | 1 |
| KD***60 | Bracket,Center | 1 |
| KD***50 | Stopper,Piston | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Electrical System : Starting Motor And Mounting (2.8kw)
| 01***30 | Bolt | 2 |
| 07***95 | O-Ring,Transmission Strainer | 1 |
| (6***0) | Starting Motor Ass'Y,(2.8kw) (See Fig.A6210-B0b3) | 1 |
Engine Kit
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Engine Kit : Gasket Kit
| 01***12 | Washer,Lock (Noise Suppression Spec.) (K2) | 1 |
| 07***65 | O-Ring,Injection Pump Case | 1 |
| 07***85 | O-Ring,(Without Fuel Level Gauge) | 1 |
Fuel System
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Fuel System : Fuel Filter And Piping
| 01***65 | Bolt,(With Water Separator) | 2 |
| 07***12 | Gasket,Mechanical Pump Piping | 1 |
| 07***12 | Gasket,(Without Air Compressor Type) (K1) | 4 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Fuel System : Fuel Filter And Piping (For Large Capacity)(#56149-)
| 01***65 | Bolt,(With Water Separator) | 2 |
| 07***12 | Gasket,Mechanical Pump Piping | 1 |
| 07***12 | Gasket,(Without Air Compressor Type) (K1) | 4 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Fuel System : Fuel Injection Pump (Feed Pump)
| DK***20 | Bolt, Joint | 1 |
| DK***00 | Valve,Check | 2 |
| DK***20 | Pump,Priming | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Fuel System : Fuel Injection Pump (Governor) (1/2)
| DK***00 | Shim? 2.00mm,(High Altitude Spec.) | 0 |
| DK***00 | Adapter | 1 |
| DK***80 | Nut | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Fuel System : Fuel Injection Pump (Governor) (2/2)
| DK***20 | Lever | 1 |
| DK***40 | Gasket,Air Compressor | 2 |
| DK***20 | Capsule,Spring | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Fuel System : Fuel Injection Pump (Pump) (1/2)
| 62***10 | Injection Pump Ass'Y | 1 |
| 62***11 | Injection Pump Ass'Y | 1 |
| DK***30 | Bearing | 0 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Fuel System : Fuel Injection Pump (Pump) (2/2)
| DK***40 | Shim? 0.50mm, Shim, 0.50mm; Was Dk029311-0040 | 0 |
| DK***90 | Shim? 0.25mm, Shim, 0.25mm; Was Dk029311-0590 | 0 |
| DK***00 | Sleeve,Control | 4 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Fuel System : Fuel Injection Pump And Piping
| 01***35 | Stud | 4 |
| 01***12 | Bolt | 2 |
| 01***25 | Screw | 2 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Fuel System : Fuel Nozzle And Spill Pipe
| 07***50 | Tube,Spill | 1 |
| 07***55 | Tube,Spill | 1 |
| 07***85 | Clip | 2 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Fuel System : Water Separator And Piping(#43240-)
| 01***80 | Stud | 2 |
| 01***25 | Bolt,(With Corrosion Resistor) | 2 |
| 01***08 | Nut,See Fig. K4010-04a0 | 2 |
Lubricating Oil System
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Lubricating Oil System : Lubricating Oil Filter
| 60***40 | Cartridge,Engine Oil Filter (D31s) | 1 |
| 60***41 | Cartridge,Engine Oil Filter (D31s) | 1 |
| 60***20 | Plate? Caution,(Italian-English) | 1 |
Komatsu : 4d95s-W-1f-A(S/N 23318-Up) : Lubricating Oil System : Lubricating Oil Pump And Suction Pipe
| 01***12 | Bolt,(See Fig.0501) | 1 |
| 01***16 | Screw | 6 |
| 01***55 | Bolt,(With Engine Stop Motor Type) | 1 |
4D95S-W-1F-A(S/N 23318-UP) serial number reference
The engine serial number plate is located on or near the valve cover on the left side of the engine block. The prefix is the first six characters of the machine model code (e.g., D20PL-6) found on the chassis data plate, which identifies the specific dozer series requiring the 4D95S-W-1F engine.
| Prefix | Identifies | Notes |
|---|---|---|
| D20PL-6 | Dozer | Series: D20PL-6 / D20PLL-6. Engine fitted: 4D95S-W-1F. Engine serial range: 23318-Up. Rough years: Not documented for this exact serial range — verify with your dealer. |
| D20Q-6 | Dozer | Series: D20Q-6 / D20S-6. Engine fitted: 4D95S-W-1F. Engine serial range: 23318-Up. Rough years: Not documented for this exact serial range — verify with your dealer. |
Frequently asked questions
What is the engine type?
The Komatsu 4D95S-W-1F-A is a four-cylinder, water-cooled, direct-injection diesel engine with electronic fuel control.
What is the operating weight?
Operating weight varies by configuration, typically ranging from 15,000 to 20,000 kg (33,000 to 44,000 lb) depending on the D20/D21 dozer model and undercarriage setup.
What replaced it?
The 4D95S-W-1F-A was replaced by the SAA4D95LE-6 engine in the 7th generation D21A-7 series dozers, which met stricter Tier 4/Stage III emissions standards.
What 4D95S-W-1F-A(S/N 23318-UP) owners discuss
What are the known powertrain and hydraulic behaviors for the Komatsu 4D95S-W-1F-A engine?
What undercarriage or wear patterns are typical for machines powered by this engine series?
What are the specific engine quirks per the 4D95S-W-1F-A series?
What are common electrical or sensor issues reported by owners?
What should be checked when buying a used machine with the 4D95S-W-1F-A (S/N 23318-UP) engine?
What fluids are recommended for this engine and its associated systems?
What is a safety-critical fix associated with the fuel system on this engine?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
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