Komatsu 4D95S-W-1F-S(S/N 23318-UP)
Maintenance schedule, common problems & OEM parts breakdown
The Komatsu 4D95S-W-1F-S engine is a 4-cylinder, 3.05-liter diesel powerplant designed for the D20 and D21 series crawler dozers (specifically models D20A, D20P, D20S, D20Q, D20PL, D20PLL, D21A, D21P, D21S, D21Q, D21AG, D21QG, and D21E). This engine powers mid-size dozers with operating weights ranging from approximately 12,000 to 15,000 lbs (5,400 to 6,800 kg). Production for this specific engine configuration in these dozer models spans the late 1990s through the early 2000s, covering the Dash-6 and Dash-7 generations. It succeeded earlier 3D95S variants and was eventually replaced by the SAA4D95LE series in later Dash-8 and newer generations to meet stricter emissions standards. Configurations offered include standard air-to-air aftercooled versions for heavy-duty earthmoving and grading applications.
Across the Dash-6 to Dash-7 transition, the primary change for the 4D95S-W-1F-S was the integration of electronic engine management systems and improved fuel injection precision, moving away from purely mechanical governor controls found in earlier 3D95S models. The machine remains significant in the used and parts market because the D20/D21 series is a high-volume workhorse in municipal, agricultural, and light construction sectors. The 4D95S engine is widely supported by aftermarket rebuild kits and is known for robustness, making it a common target for re-engining projects in older dozers and forklifts (such as the FD25) that originally used similar 4D95S variants. Its compact size and durability ensure a steady demand for core components like pistons, liners, and injectors.
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-S(S/N 23318-UP) specifications
Engine
| Model | 4D95S-W-1F-S |
| Series | 95 Series |
| Displacement | 3.05 L (186 cu in) |
| Cylinders | 4 |
| Net Power | 137 hp (102 kW) |
| Emissions Tier | Tier 4 Final / Stage V |
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)
| 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 |
| 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 |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
Komatsu 4D95S-W-1F-S(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-S(S/N 23318-UP) beyond the schedule
Predictive Maintenance & Fluid Analysis
Utilize Komatsu KOWA fluid analysis at every 500-hour interval to monitor engine wear metals (iron, copper, lead) and contaminants (silicon, sodium). Check coolant SCA concentration at 500 hours to prevent liner cavitation in the 4D95S-W-1F-S block. Monitor hydraulic oil particle count and viscosity to protect the injection pump and valve train. Track fuel dilution and soot levels in engine oil to determine optimal drain intervals based on actual operating conditions rather than fixed schedules alone.
Corrective & Common Repairs
Address common 4D95S-W-1F-S issues by inspecting piston height variants (95mm vs 115mm) during any top-end work to prevent compression loss. Check for injector leakage and timing gear wear, which can cause poor rev-up and running trouble. Inspect the head gasket and cylinder liners for roughness or scoring, common in high-hour D20/D21 dozers. Verify turbocharger shaft play and inspect air filter restriction indicators frequently to prevent dust ingestion and premature wear in the intake system.
Overhaul & Rebuild Points
Plan for an inframe or full overhaul when valve adjustment becomes difficult or compression drops below specification. Key rebuild components for the 4D95S-W-1F-S include cylinder liners, pistons, piston pins, and rod bearings. Use STD size pistons unless machining requires oversize. Replace all gaskets, seals, and O-rings during disassembly. Inspect the crankshaft for journal wear and check the camshaft lobes for pitting. Ensure proper torque sequence for head bolts to prevent warping.
Seasonal & Environment Servicing
In cold climates, ensure coolant glycol concentration is adequate to prevent block freezing and maintain heater core function. Drain water from the fuel separator daily to prevent injector damage from ice or microbial growth. In dusty environments, clean radiator and oil cooler fins frequently to prevent overheating. Check belt tension and hose condition more often in extreme heat to avoid failure. Use Komatsu EO or equivalent diesel engine oil with the correct viscosity grade for ambient temperatures.
4D95S-W-1F-S(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-S(S/N 23318-UP) fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| CA115 | Engine crankshaft speed sensor failure | Faulty sensor, broken wiring, or corroded connector at the pin interface | Replace the speed sensor and verify voltage at the pin connector |
| CA111 | Internal engine controller fault | Electronic Control Module (ECM) internal failure | Replace or reprogram the ECM |
| CA451 | Common rail pressure sensor feedback value too high | Malfunctioning rail pressure sensor or actual overpressure condition | Diagnose the fuel rail pressure sensor or check pump lines |
| CA441 | Battery voltage too low | Weak battery, failing alternator, or poor connections | Replace the alternator or battery; check the voltage regulator |
| CA122 | Intake air pressure sensor feedback voltage too high | Sensor malfunction or wiring issue | Verify the intake pressure sensor and wiring |
| CA234 | Engine overspeed | Throttle calibration error, engine load cycle issue, or operator misuse | Verify throttle calibration and engine load cycle |
| CA153 | Intake air temperature sensor feedback voltage too high | Faulty Intake Air Temperature (IAT) sensor | Replace or test the IAT sensor |
| CA2311 | IMV solenoid valve failure | Failed IMV solenoid or wire harness issue | Replace the IMV solenoid or inspect the wire harness |
| CA428 | Fuel moisture sensor invalid voltage | Contaminated fuel supply or sensor harness fault | Ensure a clean fuel supply and check the moisture sensor harness |
| CA442 | Battery voltage too high | Failing voltage regulator or alternator overcharging | Replace the alternator or battery; check the voltage regulator |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
4D95S-W-1F-S(S/N 23318-UP) attachments & work tools
Dozer Blade Configurations
The 4D95S-W-1F-S engine (S/N 23318-UP) powers the D20 and D21 series crawler dozers, specifically models such as the D20PL-6, D20PLL-6, D20Q-6, and D20S-6. These machines utilize standard straight (S) or semi-universal (SU) dozer blades appropriate for the 10-12 ton operating weight class.
Ripper Configurations
Factory configurations for the D20/D21 series include single-shank or multi-shank ripper options mounted to the rear frame. Ripper shank geometry and penetration depth vary by configuration and series, typically ranging from 300 mm to 600 mm for this class.
Coupler/Mounting Systems
The D20/D21 dozer frame utilizes a fixed mounting system for the dozer blade and ripper, secured via heavy-duty pins and bushings. No quick-attach coupler system is standard for this engine/machine class; attachments are mounted using fixed frame brackets.
Hydraulic Kit/Arrangement Notes
Dozer and ripper operation requires auxiliary hydraulic circuits routed through the main control valve. Factory specifications mandate Komatsu EO or equivalent high-quality hydraulic fluid for the system; verify specific flow rates and pressure settings with the machine's operation and maintenance manual.
Notable Factory Configurations/Guarding
Factory guarding options for this engine and dozer class include heavy-duty undercarriage guards, side skirts, and engine compartment screens. Specific guarding availability varies by configuration and series, often dependent on regional emissions and safety standards.
All 4D95S-W-1F-S(S/N 23318-UP) assemblies by section
Every catalogued assembly group for the Komatsu 4D95S-W-1F-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(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-S(S/N 23318-UP) serial number reference
The engine serial number plate is located on the engine block, typically on the left side near the injection pump or on a metal plate affixed near the valve cover. The serial number is stamped directly onto the engine block. The prefix '23318' indicates the start of the serial range for this specific engine variant; it is not a 3-character machine PIN prefix.
| Prefix | Identifies | Notes |
|---|---|---|
| 23318 | 4D95S-W-1F-S | Engine serial number break. S/N 23318-UP identifies this specific engine configuration variant within the 4D95S-W-1F family. The prefix '23318' is the start of the sequential engine serial range, not a 3-character machine PIN prefix. No 3-character PIN prefixes are documented for this engine serial range in the provided sources. |
Frequently asked questions
What is the engine model for the Komatsu 4D95S-W-1F-S?
The engine model is the Komatsu 4D95S-W-1F-S, a 4-cylinder, 3.05-liter diesel engine with an air-to-air aftercooler.
What is the operating weight of the machines powered by this engine?
The operating weight varies by configuration and series, typically ranging from 12,000 to 15,000 lbs (5,400 to 6,800 kg) for the D20 and D21 series dozers.
What engine replaced the 4D95S-W-1F-S in later Komatsu models?
The SAA4D95LE series engine replaced the 4D95S family in later Dash-8 and newer generation Komatsu dozers to meet Tier 4 Final/Stage V emissions standards.
What 4D95S-W-1F-S(S/N 23318-UP) owners discuss
What are the known powertrain and hydraulic behaviors for the Komatsu 4D95S-W-1F-S engine?
What undercarriage or wear patterns are typical for machines powered by this engine series?
What are the common engine quirks per the 4D95S-W-1F-S series?
What are the common electrical or sensor issues associated with this engine?
What should be checked when buying a used machine with the 4D95S-W-1F-S engine (S/N 23318-UP)?
What fluid specifications are recommended for the Komatsu 4D95S-W-1F-S engine and associated systems?
What is a safety-critical fix related to 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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