Komatsu 4D95S-W-1G-AP(S/N 23318-UP)
Maintenance schedule, common problems & OEM parts breakdown
The Komatsu 4D95S-W-1G-AP is a 4-cylinder, water-cooled, turbocharged diesel engine belonging to the 95 Series family. It powers the GD85A and GD105A motor grader series, which are mid-size earthmoving machines designed for heavy grading and road construction. Production for this engine configuration spans the late 1990s through the early 2000s, serving as the powerplant for the transition from the earlier GD75A/GD100A predecessors to the later GD105P/125P successors. The engine is rated at approximately 137 horsepower, providing the torque necessary for the machine's operating weight range and hydraulic demands.
Across the 95 Series generations, the 4D95S-W-1G-AP represents a mature, mechanically controlled platform that predates the widespread adoption of electronic engine management and Tier 4 emissions systems. This mechanical simplicity is the primary driver of its enduring value in the used and parts market. Unlike newer electronic engines that require specialized diagnostic tools and expensive emission control components, the 4D95S-W-1G-AP relies on robust, easily serviceable mechanical fuel injection and hydraulic lifters. This makes it a preferred choice for independent repair shops and fleet managers seeking cost-effective, long-term reliability in older motor graders and industrial applications.
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-AP(S/N 23318-UP) specifications
Engine
| Model | 4D95S-W-1G-AP |
| 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 | 137 hp (102 kW) |
| Net Power | 137 hp (102 kW) |
| 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)
| Engine Oil Capacity | Not documented for this exact serial range — verify with your dealer |
| Cooling System Capacity | Not documented for this exact serial range — verify with your dealer |
| Hydraulic System Capacity | Not documented for this exact serial range — verify with your dealer |
| Fuel Tank Capacity | 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-AP(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-AP(S/N 23318-UP) beyond the schedule
Predictive Maintenance & Fluid Analysis
Utilize Komatsu KOWA fluid analysis at every major service interval to monitor wear metals and contaminants. Track iron, copper, and lead levels in the engine oil to detect internal bearing or cylinder liner wear early. Analyze hydraulic fluid for ISO cleanliness codes and water content to prevent pump and valve corrosion. Monitor coolant pH and SCA concentration to ensure proper corrosion inhibition for the aluminum and steel components within the 4D95S-W-1G-AP cooling system.
Corrective & Common Repairs
Address frequent 4D95S-W-1G-AP issues by inspecting the mechanical fuel injection pump for internal wear and leakage. Check the water pump and thermostat housing for coolant leaks that can lead to overheating. Inspect the turbocharger shaft play and seals for oil consumption or boost loss. Replace worn valve tappets and push rods if valve clearance exceeds specifications, as improper adjustment causes poor combustion and excessive soot.
Overhaul & Rebuild Points
Plan for an inframe overhaul when compression drops significantly or oil consumption exceeds operational limits. The 4D95S-W-1G-AP requires specific piston height verification (95mm or 115mm variants) to ensure correct compression ratio and performance.
Seasonal & Environment Servicing
In cold climates, ensure the coolant mixture provides adequate freeze protection and use low-viscosity engine oil for cold starts. In dusty environments, service the air cleaner more frequently and monitor the restriction indicator closely to prevent abrasive wear. In high-temperature conditions, keep the radiator and oil cooler fins clean of debris to maintain optimal operating temperatures. Check the battery electrolyte levels and charge status regularly, as extreme temperatures accelerate battery degradation. Adjust fuel injection timing if necessary to compensate for altitude changes.
4D95S-W-1G-AP(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-AP(S/N 23318-UP) fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| CA115 | Engine crankshaft speed sensor and backup speed sensor failure | Faulty speed sensor, broken wiring harness, or corroded connector at the pin connector | Replace the speed sensor and verify voltage at the pin connector |
| CA441 | Battery voltage too low | Weak battery, failing alternator, or loose connections | Replace the battery or alternator and check the voltage regulator |
| CA442 | Battery voltage too high | Faulty voltage regulator or alternator malfunction | Replace the alternator or battery and check the voltage regulator |
| CA122 | Intake air pressure sensor feedback voltage too high | Faulty intake pressure sensor or wiring issue | Verify the intake pressure sensor and wiring |
| CA123 | Intake air pressure sensor feedback voltage too low | Sensor short circuit or airflow restriction | Check for a sensor short or an airflow restriction |
| CA153 | Intake air temperature sensor feedback voltage too high | Faulty intake air temperature (IAT) sensor | Replace or test the IAT sensor |
| CA154 | Intake air temperature sensor feedback voltage too low | Faulty intake air temperature (IAT) sensor | Replace or test the IAT sensor |
| CA451 | Common rail pressure sensor feedback value too high | Malfunction in the rail sensor or actual overpressure condition | Diagnose the fuel rail pressure sensor or pump lines |
| CA452 | Common rail pressure sensor feedback value too low | Fuel leak, sensor failure, or supply pump issue | Diagnose the fuel rail pressure sensor or pump lines |
| CA234 | Engine overspeed | Throttle calibration error, engine load cycle issue, or operator misuse | Verify throttle calibration and engine load cycle |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
4D95S-W-1G-AP(S/N 23318-UP) attachments & work tools
Dozer Blade Configurations
The Komatsu D20 and D21 series machines powered by the 4D95S-W-1G-AP engine utilize semi-universal (SU) and straight (ST) blade configurations. Factory specifications for these models include standard and heavy-duty blade options tailored for earthmoving and grading tasks.
Ripper Attachments
Single-shank and multi-shank ripper options are available for the D20 and D21 dozer platforms. These attachments are mounted to the rear frame and require specific hydraulic line routing for depth control and lift functions, varying by machine serial number and frame configuration.
Undercarriage & Track Shoes
The machine class supports standard and wide track shoe configurations to adjust ground pressure. Track frame dimensions and shoe width options are selected based on the specific dozer model (D20 or D21) and intended operating conditions, with mounting interfaces standardized for the series.
Hydraulic Coupler Systems
Quick coupler systems for dozer blades are available as factory options or dealer-installed accessories. These systems require specific hydraulic valve blocks and hose arrangements integrated into the machine's main hydraulic circuit to allow for blade angle adjustment from the operator's cab.
Engine Guarding & Protection
Factory configurations include heavy-duty radiator screens, stone guards, and undercarriage protectors for the D20/D21 series. These components are designed to prevent debris ingestion and damage in rocky or abrasive environments, with specific mounting points defined by the machine's frame serial range.
All 4D95S-W-1G-AP(S/N 23318-UP) assemblies by section
Every catalogued assembly group for the Komatsu 4D95S-W-1G-AP(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(S/N 23318-Up) : Electrical System : Alternator And Mounting (25a)
Komatsu : 4d95s-W-1g-Ap(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-Ap(S/N 23318-Up) : Electrical System : Starting Motor And Mounting (2.8kw)
Engine Kit
Komatsu : 4d95s-W-1g-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-Ap(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-1G-AP(S/N 23318-UP) serial number reference
The engine serial plate is stamped on the engine block, typically on the left side near the injection pump. Read the prefix (e.g., 4D95S-W-1G-AP) to identify the engine model, then verify the numeric serial number against the 23318-UP range to confirm fitment for this specific configuration.
| Prefix | Identifies | Notes |
|---|---|---|
| 4D95S-W-1G-AP | Engine Model | Identifies the specific engine configuration for the 4D95S-W-1G-AP family. Serial range starts at 23318. Source: Buymachineryparts application list ties this prefix to S/N 23318-UP. Factory spec sheet for the 4D95S-W-1G-AP engine confirms the S/N 23318-UP range for this catalog variant. |
Frequently asked questions
What is the engine type for the Komatsu 4D95S-W-1G-AP?
It is a 4-cylinder, water-cooled, turbocharged diesel engine from the Komatsu 95 Series family, rated at approximately 137 horsepower.
What is the operating weight of the machine powered by this engine?
The operating weight varies by configuration and series, typically ranging from 9,182 to 87,083 lb depending on the specific motor grader model and attachment package.
What replaced the 4D95S-W-1G-AP engine?
It was succeeded by later 95 Series variants and newer engine families that meet stricter emissions tiers, such as the 4D95LE and SAA4D95LE series, which incorporate electronic control and advanced emission reduction technologies.
What 4D95S-W-1G-AP(S/N 23318-UP) owners discuss
What is the typical power output and application for the 4D95S engine series?
What are the common fuel system quirks and troubleshooting steps for the 4D95S engine?
What are the known issues with piston height during rebuilds of the 4D95S-W engine?
What are the typical undercarriage and wear patterns for machines powered by this engine series?
What electrical or sensor issues are commonly discussed for the 4D95S engine?
What fluids are recommended for the Komatsu 4D95S engine series?
What should be checked when buying a used machine with the 4D95S-W-1G-AP engine?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
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