Komatsu 4D95S-W-1G-P(S/N 23318-UP)
Maintenance schedule, common problems & OEM parts breakdown
The Komatsu 4D95S-W-1G-P is a 4-cylinder, water-cooled, turbocharged diesel engine belonging to the 95 Series family. It powers compact to mid-size construction equipment, including the D20 and D21 series crawler dozers and the WA50 wheel loader. Production years for this specific engine configuration span the late 1990s through the early 2000s, serving as a predecessor to later Tier 3 and Tier 4 compliant powerplants. Configurations offered include standard and wide-track (LGP) applications for dozers and standard wheel loader mounts, with operating weights for the host machines ranging from approximately 12,000 lb to 20,000 lb depending on the attachment package and undercarriage setup.
Across the 95 Series generation, the 4D95S-W-1G-P represents a transition point in Komatsu's engine lineup, moving from naturally aspirated predecessors to turbocharged variants optimized for higher torque and fuel efficiency in compact frames. The machine matters in the used and parts market today because it is a high-volume power unit for the D20/D21 dozer and WA50 loader platforms, which remain ubiquitous in rental fleets and small-to-medium earthmoving operations. Its widespread use ensures a robust aftermarket ecosystem for rebuild kits, pistons, and liners, while its serial range (23318-UP) helps buyers distinguish between early and late production variants that may have different piston heights or electrical configurations.
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-1G-P(S/N 23318-UP) specifications
Engine
| Model | 4D95S-W-1G-P |
| 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 | not documented for this exact serial range — verify with your dealer |
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-1G-P(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-1G-P(S/N 23318-UP) beyond the schedule
Predictive Maintenance & Fluid Analysis
Utilize KOWA fluid analysis at every 500-hour interval to monitor wear metals (iron, copper, lead) and contaminants (silicon, sodium) in the 4D95S-W-1G-P engine oil. Track hydraulic fluid particle count and viscosity to detect pump or valve wear in the WA50 loader or D21 dozer systems. Monitor coolant pH and SCA concentration to prevent liner cavitation in the 3.05L block. Early detection of fuel dilution or soot buildup in the oil helps prevent premature bearing failure in this high-compression diesel engine.
Corrective & Common Repairs
Address common 4D95S-W-1G-P failures by verifying piston height (95mm vs. 115mm variants) before any rebuild to avoid compression loss. Replace worn cylinder liners and pistons if blue smoke or excessive oil consumption indicates bore wear. Inspect the turbocharger and charge air cooler for leaks that reduce torque output. Check the fuel injection pump and injectors for clogging or leakage, which cause rough idling and hard starting in D20/D21 dozer applications.
Overhaul & Rebuild Points
Plan major engine overhaul at 10,000–12,000 hours or when compression drops below specification. Replace all four cylinder liners, pistons, rings, and bearings using a complete overhaul kit. Inspect the crankshaft for journal wear and the camshaft for lobe degradation. Re-machine the cylinder head and replace valve guides and seats to restore combustion efficiency. Ensure correct gasket sets are used for the specific serial range to prevent coolant or oil leaks.
Seasonal & Environment Servicing
In cold climates, ensure the cooling system uses Komatsu Super Coolant AF-NAC to prevent freezing and corrosion. Check the battery charge and insulation in winter conditions. In dusty environments, inspect the air filter restriction indicator daily and clean the radiator and oil cooler fins frequently to prevent overheating. Verify the fuel water separator is drained regularly to prevent microbial growth in the tank. Adjust track tension on D20/D21 dozers for muddy or rocky terrain to reduce undercarriage wear.
4D95S-W-1G-P(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-1G-P(S/N 23318-UP) fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| CA115 | Engine crankshaft speed sensor failure | Faulty crankshaft speed sensor, broken wiring harness, or corroded connector at the sensor pin. | Inspect the sensor wiring and connector for damage or corrosion. Replace the speed sensor if voltage readings are out of specification. |
| CA441 | Battery voltage too low | Weak or discharged battery, failing alternator, or loose/corroded battery cables. | Check battery terminal tightness and corrosion. Test battery charge and alternator output voltage. |
| CA442 | Battery voltage too high | Failing voltage regulator, faulty alternator, or loose alternator drive belt. | Inspect the alternator belt tension and condition. Test the alternator output and voltage regulator function. |
| CA122 | Intake air pressure sensor feedback value too high | Faulty intake air pressure sensor, restricted air filter, or boost leak. | Check the air filter element for clogging. Inspect the sensor wiring and connector. Verify sensor voltage output against specifications. |
| CA123 | Intake air pressure sensor feedback value too low | Faulty intake air pressure sensor, air intake restriction, or sensor short circuit. | Check for air intake restrictions. Inspect the sensor harness for shorts. Test the sensor signal voltage. |
| CA451 | Common rail pressure sensor feedback value too high | Faulty rail pressure sensor, actual overpressure condition, or sensor wiring issue. | Diagnose the fuel rail pressure sensor circuit. Check for actual overpressure conditions in the fuel system. |
| CA452 | Common rail pressure sensor feedback value too low | Faulty rail pressure sensor, low fuel pressure, or sensor circuit open. | Check the fuel supply pressure. Inspect the rail pressure sensor wiring and connector for opens or shorts. |
| CA2311 | IMV (Idle Management Valve) solenoid valve failure | Failed IMV solenoid, shorted or open solenoid circuit, or contaminated valve. | Inspect the IMV solenoid wiring harness. Replace the IMV solenoid valve if the circuit is intact but the valve is faulty. |
| CA111 | Internal engine controller fault | Critical failure within the Electronic Control Module (ECM). | Check ECM power and ground connections. If connections are good, the ECM may require replacement or reprogramming. |
| AA10NX | Air cleaner clogging | Clogged air filter element or restricted intake path. | Replace the air filter element. Inspect the intake ducting for obstructions. |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
4D95S-W-1G-P(S/N 23318-UP) attachments & work tools
Bulldozer Blade Configurations
The 4D95S-W-1G-P engine (S/N 23318-UP) is specified for the Komatsu D20 and D21 series crawler dozers, specifically the D20P-6, D20PL-6, D21P-6, and D21S-6 models. Typical blade options for this class include the semi-U (SU) blade for general dozing and the universal (U) blade for heavy material handling, with blade widths ranging from approximately 2.4 to 2.9 meters depending on the specific dozer model variant.
Ripper Attachments
Factory configurations for the D20/D21 series include single-shank or multi-shank rippers for soil breaking and rock loosening. Ripper shank lengths and widths vary by configuration, typically ranging from 1.2 to 1.5 meters in length, with mounting points integrated into the rear frame structure of the dozer chassis.
Hydraulic Coupler Systems
Work tools requiring auxiliary hydraulics, such as hydraulic breakers or mulchers, utilize the standard Komatsu quick-coupler system mounted on the blade or frame. Hydraulic flow requirements for these attachments typically range from 100 to 150 liters per minute, necessitating the installation of auxiliary hydraulic kits and high-pressure hose assemblies specific to the D20/D21 series.
Engine Guarding and Options
Factory guarding options for this engine class include heavy-duty air pre-cleaners and cyclone filters for dusty environments, along with extended radiator screens. Additional options often include cold-start aids for low-temperature operation and specific exhaust silencer configurations to meet regional noise regulations.
All 4D95S-W-1G-P(S/N 23318-UP) assemblies by section
Every catalogued assembly group for the Komatsu 4D95S-W-1G-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(S/N 23318-Up) : Cylinder Block : Flywheel And Flywheel Housing
| 01***30 | Bolt | 6 |
| 01***30 | Bolt - Lower Oil Cooler Outlet Tubemounting | 11 |
| 01***45 | Bolt, Bracket Mounting | 8 |
Komatsu : 4d95s-W-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(S/N 23318-Up) : Cylinder Head : Exhaust Manifold And Muffler (Tunnel Spec.)(#23342-)
| 01***25 | Grub Screw | 4 |
| 01***16 | Bolt - Starting Motor Ground Cable | 1 |
| 01***45 | Bolt, Bracket Mounting | 6 |
Komatsu : 4d95s-W-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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-1g-P(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 |
Frequently asked questions
What is the engine type for the Komatsu 4D95S-W-1G-P?
It is a 4-cylinder, water-cooled, turbocharged diesel engine from the Komatsu 95 Series family, with a displacement of approximately 3.05 liters.
What is the operating weight of the machines powered by this engine?
Operating weight varies by configuration and series. Host machines like the D20 and D21 dozers and WA50 wheel loader typically range from 12,000 lb to 20,000 lb depending on the attachment package and undercarriage setup.
What replaced the 4D95S-W-1G-P engine?
The 4D95S-W-1G-P was succeeded by later 95 Series variants and subsequent Tier 3 and Tier 4 compliant engines as emissions regulations tightened, with specific replacement models varying by machine platform and production year.
What 4D95S-W-1G-P(S/N 23318-UP) owners discuss
What are the typical powertrain and hydraulic behaviors associated with the Komatsu 4D95S-W-1G-P engine series?
What undercarriage or wear patterns are typical for machines powered by this engine type?
What are the known engine quirks for the 4D95S-W-1G-P series?
What are the common electrical or sensor issues reported for this engine?
What fluids and specifications are recommended for the Komatsu 4D95S-W-1G-P engine?
What should be checked when buying a used machine with the 4D95S-W-1G-P engine?
How does the 4D95S-W-1G-P engine handle emissions and fuel efficiency?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
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