Komatsu 4D95S-1J(S/N 124813-UP)

The 4D95S-1J is a 4-cylinder, 3.3-liter (201 cu in) direct-injection diesel engine. It is commonly found in Komatsu GD85A and GD105A bulldozers and PC80/PC95/PC120 excavators. Rated power varies by configuration/series, typically ranging from 60 to 80 horsepower (45 to 60 kW) at approximately 2,200 rpm. The engine is noted for fuel efficiency and smooth operation. Hydraulic systems in these machines are generally reliable but sensitive to contamination; if the hydraulic pump fails, the engine is often not far behind due to shared wear patterns in high-load applications. The 4D95S is the most powerful version in the basic 4D95 line, often producing about 137 horsepower in specific high-output configurations, though standard ratings for the 1J series are lower. The engine utilizes a mechanical fuel system in earlier iterations, relying on simple parts for fuel control, while later serial ranges may incorporate electronic controls depending on the machine tier. Fluids recommended include Komatsu EO diesel engine oil, TO powertrain oil, and AF-NAC super-coolant. Hydraulic oil specifications typically align with ISO VG46 or Komatsu HO standards. Axle oil should meet Komatsu AXO80 specifications (SAE 80WZF). Powertrain oil often requires Komatsu TO10 (SAE 10W) or TO30 (SAE 30W) API CD grades. Coolant capacity varies by machine model; for reference, similar Komatsu excavators like the PC200LC-7/8 use approximately 2.6 gallons (9.8 liters) for the cooling system, with operating temperatures between 180-190 degrees F (82-88 degrees C). Fan belt deflection should be checked at 0.50 in (13 mm). Note: Specific capacities for the 4D95S-1J vary by the host machine (dozer vs. excavator) and configuration/series. Have your dealer verify exact fluid capacities for your specific serial number range.

Machines equipped with the 4D95S-1J (such as GD series dozers and PC series excavators) are known for smooth operation and fuel efficiency. However, the Komatsu line is often criticized for poor resale value because the design tends to wear out complete machines simultaneously rather than individual components failing in isolation. If the hydraulic pump shows significant wear, the engine and other drivetrain components are likely nearing end-of-life. Undercarriage wear is accelerated in high-dust environments and continuous load applications. Operators should monitor ground pressure and track shoe wear closely, as these machines are often used in heavy earthmoving where undercarriage life is a primary cost factor. Early Dash 6 machines had reported valve problems, particularly on PC150 and PC120 models, which may affect hydraulic response and engine load. Regular inspection of the undercarriage for pin-and-bushing wear is critical to prevent premature failure of the final drives and swing bearings.

The 4D95S-1J (S/N 124813-Up) is part of the 95 Series engine family. A key mechanical quirk is that the 95 Series engines do not have replaceable cylinder liners; they are solid blocks. Rebuilds require oversize pistons rather than liner replacement kits. This differs from other Komatsu series that use wet liners. The engine is often confused with the Cummins 3.3T due to shared architecture, but they are distinct; using the wrong rebuild kit can lead to failure. The mechanical fuel system in earlier variants requires precise timing adjustments. If the pump is removed, timing must be rechecked using a dial gauge and special tools for rotary distributor types, or a simple procedure for inline pumps. Injector pipes must be blown out with compressed air before reinstallation to prevent dust from jamming the injector needle. The engine is robust but sensitive to fuel contamination; reconditioned injectors often fail if not calibrated by a specialist diesel shop with new tips. The fuel stop solenoid can fail, but a manual cable stop is a functional and reliable alternative. Exhaust in the cooling system is a known failure mode if the cylinder head or block cracks, requiring sleeve removal for inspection.

Komatsu excavators and dozers with the 4D95S series rely heavily on electronic control systems. A single faulty sensor or unstable power supply can trigger multiple warning signals, leading to intermittent starting, dashboard failures, or random shutdowns. Owners often report these symptoms as mysterious electrical gremlins, but they are frequently caused by sensor drift or wiring harness degradation rather than engine mechanical failure. The fuel stop solenoid is a common electrical failure point; if it fails, the engine can be stopped manually via cable, which is considered just as effective for shutdown purposes. Intermittent starting is often linked to unstable power supply to the ECU or sensors rather than the starter motor itself. Regular inspection of ground connections and sensor wiring integrity is recommended to prevent these issues.

When purchasing a used machine with the 4D95S-1J engine (S/N 124813-Up), verify the exact engine identification plate to confirm the serial range, as parts and specifications vary by configuration/series. Check for exhaust in the cooling system, a common failure mode indicating cracked sleeves or head gasket issues. Inspect the hydraulic pump for wear, as pump failure often correlates with engine wear in this series. Test the fuel stop solenoid operation; if it fails, ensure the manual cable stop is functional. Check for air in the fuel lines if the engine runs poorly, as this indicates leaks or faulty injectors. Verify the timing if the pump has been removed. Look for signs of undercarriage wear, as Komatsu machines often wear out completely. Ensure the correct fluids are used: Komatsu EO engine oil, TO powertrain oil, and AF-NAC coolant. Confirm the machine's serial number matches the parts catalog, as gray market or early Dash 6 machines may have different valve configurations and parts availability. Have your dealer verify the engine serial number against the specific machine model to ensure correct parts sourcing.

The 4D95S-1J (S/N 124813-Up) is distinct from the 4D95S-W-1G-E (S/N 23318-Up) and other 4D95S variants. The 4D95S-W series is often associated with Komatsu Yanmar derivatives and may have different timing gear configurations. The 4D95S-1J is specifically listed in the 95 Series engine parts catalog for machines like the D21QG-7/D21S-7 dozers. The 4D95S-W-1G-E is listed separately for different serial ranges. The 4D95S-1J does not have liners, requiring oversize pistons for rebuilds, whereas some other variants may have different block constructions. The 4D95S-1J is typically found in GD85A/GD105A dozers and PC80/PC95/PC120 excavators. The 4D95S-W series is often found in older FD20/30 forklifts and other material handling equipment. Power output and emissions configurations vary by the specific variant and machine application. Have your dealer verify the exact engine model plate to ensure correct parts and service procedures.

Maintenance intervals for the 4D95S-1J vary by configuration/series and operating conditions. General recommendations include regular oil changes using Komatsu EO diesel engine oil, with viscosity selected based on ambient temperature (e.g., SAE 10W or 15W-40). Hydraulic oil should meet Komatsu HO or ISO VG46 standards. Powertrain oil should be Komatsu TO10 (SAE 10W) or TO30 (SAE 30W) API CD grade. Axle oil should be Komatsu AXO80 (SAE 80WZF). Coolant should be Komatsu AF-NAC super-coolant. Filter changes are critical; use genuine Komatsu filters or high-quality equivalents. The cooling system capacity varies by machine; for reference, similar Komatsu excavators use approximately 2.6 gallons (9.8 liters). The transmission fluid capacity for forklift variants like the FD25 is approximately 10.4-11.2 quarts (9.8-10.6 liters) of Torqflow Dexron ATF. Pump pressure should be checked at 154-212 PSI. Relief pressure is typically 2,650 PSI for hydraulics and 1,350 PSI for steering. Have your dealer verify exact intervals and capacities for your specific machine model and serial number.