Komatsu S6D125-1FF(S/N 24781-UP)
Maintenance schedule, common problems & OEM parts breakdown
The Komatsu S6D125-1FF engine (S/N 24781-UP) is a 6-cylinder, 11-liter diesel powerplant used in mid-to-heavy class construction equipment, including the D65EX-12 dozer, PC400-5/7 excavators, and WA470 wheel loaders. Produced from approximately 1994 through the 2010s, it replaced earlier 6D125 variants and was succeeded by the S6D125E-2 series. Configurations include turbocharged and aftercooled versions delivering 155 to 275 HP, with operating weights for the host machines ranging from 24,000 kg to over 80,000 kg depending on the attachment package and undercarriage setup.
Across generations, the S6D125-1FF evolved from mechanical injection to electronic control, improving torque rise and fuel efficiency while maintaining a robust wet-liner design. It remains critical in the used and parts market due to its extensive installed base in durable machines like the PC400 and D65 series. The engine's simple, serviceable architecture and high torque output make it a preferred choice for remanufacturing and long-term fleet maintenance, ensuring continued availability of core components like pistons, liners, and cylinder heads.
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 S6D125-1FF(S/N 24781-UP) specifications
Engine
| Model | S6D125-1FF |
| Displacement | 11 L (672 cu in) |
| Cylinders | 6 |
| Aspiration | Turbocharged and aftercooled |
| Power (Gross/Net) | 202 kW (275 hp) / 134 kW (180 hp) |
Weights
| Operating Weight | 24,000 kg (52,910 lb) |
Dimensions
| Transport Length | 120 cm (47 in) |
| Transport Width | 100 cm (39 in) |
| Transport Height | 125 cm (49 in) |
Performance
| Travel Speed | 2.9 km/h (1.8 mph) / 5.0 km/h (3.1 mph) |
| Bucket Digging Force | 61.3 kN (13,780 lbf) |
| Arm Digging Force | 41.5 kN (9,330 lbf) |
Service capacities (summary)
| Fuel Tank | 7.5 L (2.0 gal) |
| Engine Oil | Komatsu EO or equivalent diesel engine oil |
| Cooling System | Super-coolant AF-NAC |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
S6D125-1FF(S/N 24781-UP) fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Engine crankcase (with filter) | Not documented for this exact serial range — verify with your dealer | Komatsu Genuine Diesel Engine Oil, SAE 15W-40 for normal ambient temperatures; SAE 10W-30 is the Komatsu-approved grade for colder climates. Equivalent cross-reference: Chevron Delo 400 series diesel engine oil built to the same Komatsu engine-oil specification. |
| Cooling system | Not reliably documented for this exact serial range. Closely related earlier D-series generations of similar displacement ran roughly 42-63 L (11.1-16.6 gal), but this figure is not confirmed as applicable to the 6D125-1A S/N 10001-UP - verify with dealer | Komatsu Super Coolant, supplied as concentrate mixed 50/50 with water (extended-life, all-season, anti-corrosion coolant). No separate winter/summer concentration split is called out beyond the standard 50/50 mix; use a higher concentrate ratio only for extreme cold per Komatsu's coolant freeze-protection chart. |
| Fuel tank | 250-320 L (66-85 gal), varies by dozer model; not a fixed engine-level figure | Automotive diesel fuel (ASTM D975 No. 2-D equivalent) for normal conditions; switch to a lighter No. 1-D-equivalent fuel in cold weather per Komatsu's ambient-temperature fuel guidance. Keep tank topped up at end of shift to reduce condensation. |
| Transmission/powertrain compartments | Not separately published for this serial range. The D50A/P-17 uses a manually shifted spur-gear transmission (5 speeds forward, 4 reverse) with splash-type lubrication, sharing lubrication with the spiral bevel gear shaft and the wet multiple-disc steering clutch/band brake, per the factory specifications section; no standalone capacity figure was accessible. | Komatsu Powertrain & Micro Clutch Oil (drive-train fluid spec): SAE 10W in cold conditions, SAE 30 in normal/warm conditions. Equivalent cross-reference: Chevron Delo TorqForce in matching viscosity grade. |
| Final drives (each) | Not separately published for this serial range. Final drive is a 2-stage spur-gear reduction with splash-type lubrication per the factory specifications section; Komatsu shop literature for this chassis does not show it as an independently drained/filled compartment separate from the power train case in the data reviewed. | Komatsu Powertrain & Micro Clutch Oil, same grade as the power train case (SAE 10W cold / SAE 30 normal), unless the periodic maintenance chart calls out a dedicated final-drive fill point with Komatsu Gear Lubricant (SAE 80W-90 or 85W-140, API GL-5 class) - confirm which applies before servicing. |
| Hydraulic system and tank | No standalone hydraulic tank capacity is published; the hydraulic tank is integrated into the control valve assembly, so there is no separate reservoir on this chassis. | Komatsu hydraulic oil (46AW hydraulic fluid spec), ISO VG 46. Equivalent cross-reference: Chevron Rando HD or Delo TorqForce hydraulic-oil equivalents in ISO 46 grade. A Komatsu biodegradable hydraulic fluid option also exists under the same specification for environmentally sensitive sites. |
| Grease (spec only) | Not applicable (grease points serviced per periodic lubrication schedule, not a fill volume). | Komatsu Lithium-base Grease EP2 (G2-LI), NLGI 2, general-purpose chassis grease for normal temperatures. Equivalent cross-reference: Chevron/Delo Grease ESI EP, NLGI 2. Use a lower-consistency (arctic-grade) NLGI 1 or 0.5 lithium grease in sustained sub-freezing climates per standard Komatsu cold-weather guidance. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Komatsu S6D125-1FF(S/N 24781-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 S6D125-1FF(S/N 24781-UP) beyond the schedule
Predictive Maintenance & Fluid Analysis
Utilize KOWA fluid analysis at every major service interval to monitor wear metals (iron, copper, lead, aluminum) and contaminants (silicon, sodium) in the engine oil. Track hydraulic fluid particle count and viscosity to detect pump or valve wear early. Test coolant pH, SCA concentration, and glycol content to prevent cavitation pitting in the wet liners. Monitor charge pressure and oil pressure gauges at each start to identify trends before failure, as the splash-lubricated steering-clutch case and final drives lack independent filtration to mask contamination.
Corrective & Common Repairs
Address coolant leaks into the crankcase by verifying supplemental coolant additive levels to prevent liner pitting. Replace worn turbocharger components if exhaust steam or milky oil indicates breather issues. Inspect and replace cracked hydraulic hoses and worn pins/bushings during daily checks to prevent catastrophic failure. Check belt tension and hose clamps for leaks, and replace fuel filters to protect the injection pump. Ensure battery terminals are clean and load-tested to maintain reliable starts in cold conditions.
Overhaul & Rebuild Points
Perform inframe overhaul at high hours using piston kits (e.g., 6151-31-2150) and cylinder liners to restore compression. Replace main and rod bearings if wear metals exceed limits in oil analysis. Inspect valve seats and guides for wear during disassembly. Check crankshaft pulley and vibration damper for integrity. Replace gasket sets and seals during any major engine work. Verify turbocharger shaft play and housing condition before reassembly to ensure proper airflow and boost pressure.
Seasonal & Environment Servicing
In cold conditions, check coolant concentration and battery capacity closely, as the engine lacks electronic cold-start assist beyond glow plugs. In hot, dusty environments, shorten air cleaner service intervals and keep the radiator core clear of debris to prevent overheating. Monitor DEF levels and system functionality for Tier 4 compliance. Ensure track tension is adjusted for ground conditions to reduce undercarriage wear. Inspect ROPS/FOPS integrity and cab seals to protect operators from dust and noise.
S6D125-1FF(S/N 24781-UP) common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| 600-311-8291 | Cartridge,Fuel Filter | Fuel system service | Check fitment → |
| 6114-71-6200 | Fuel Filter Ass'Y | Fuel system service | Check fitment → |
| 6114-71-6210 | Head, Fuel Filter | Fuel system service | Check fitment → |
| 09637-30161 | Plate? Instruction,Air Cleaner (Single Element) | Air intake service | Check fitment → |
| 600-211-1230 | Cartridge,Oil Filter | Lubrication service | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
S6D125-1FF(S/N 24781-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 sensor pin | Inspect the sensor wiring and connector for corrosion or damage; replace the speed sensor if voltage is abnormal |
| CA451 | Common rail pressure sensor feedback value too high | Malfunctioning rail pressure sensor, actual overpressure condition, or sensor wiring short | Diagnose the fuel rail pressure sensor circuit and check for physical blockages in pump lines |
| CA452 | Common rail pressure sensor feedback value too low | Faulty rail pressure sensor, low fuel supply pressure, or sensor circuit open | Check the fuel supply pump and regulator; verify sensor voltage and wiring integrity |
| CA111 | Engine controller internal fault | Critical failure within the Electronic Control Module (ECM) | Replace or reprogram the ECM; verify all power and ground connections first |
| CA234 | Engine overspeed | Throttle calibration error, excessive engine load cycle, or operator misuse | Verify throttle calibration and inspect the engine load cycle for anomalies |
| CA122 | Intake air pressure sensor feedback voltage too high | Faulty intake pressure sensor or shorted wiring | Verify the intake pressure sensor operation and inspect the wiring harness for shorts |
| CA123 | Intake air pressure sensor feedback voltage too low | Sensor short circuit or significant airflow restriction upstream | Check for sensor short circuits and inspect for airflow restrictions in the intake system |
| CA441 | Battery voltage too low | Weak battery, failing alternator, or loose connections | Replace the battery or alternator; check the voltage regulator and charging circuit |
| CA442 | Battery voltage too high | Failing voltage regulator or alternator malfunction | Replace the alternator or battery; check the voltage regulator for proper output |
| AA10NX | Air cleaner clogging | Clogged air filter element due to dust or debris | Replace the air filter element immediately |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
S6D125-1FF(S/N 24781-UP) attachments & work tools
Crawler Dozer Blades
The S6D125-1FF engine (S/N 24781-Up) is fitted to the D75S-2 series dozer, which utilizes a semi-U or U-blade configuration. Factory guarding options include side cutters and wing extensions to match the blade width to the machine's track gauge.
Excavator Buckets
Compatible with the PC400-5 series excavator, this engine class supports standard digging buckets and heavy-duty rock buckets. Typical capacities vary by configuration/series, generally ranging from 2.0 to 3.0 cubic meters for the standard class, with mounting via the excavator's quick coupler system.
Wheel Loader Attachments
Used in the WA470-3 wheel loader, this engine class pairs with general-purpose and light-rock buckets. Mounting utilizes the standard loader quick-attach system, with hydraulic lines routed through the boom to operate the bucket tilt and curl functions.
Hydraulic System Configurations
The S6D125-1FF engine drives the main hydraulic pump via a direct coupling or flexible drive assembly. Hydraulic fluid specifications require Komatsu HYDO or equivalent high-viscosity index oil to maintain pump efficiency and system pressure stability.
Cooling and Guarding
The engine compartment includes a heavy-duty radiator guard and debris screen to protect the cooling core in dusty environments. Wet cylinder liners require supplemental coolant additive (SCA) maintenance to prevent cavitation erosion, as noted in the operation and maintenance manual.
All S6D125-1FF(S/N 24781-UP) assemblies by section
Every catalogued assembly group for the Komatsu S6D125-1FF(S/N 24781-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Cooling System
Komatsu : S6d125-1ff(S/N 24781-Up) : Cooling System : Cooling Fan And Mounting
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 22 |
| 01***40 | Bolt, Mount Master Brake Cylinder | 2 |
| 01***95 | Bolt,(For 2nd Travel Speed) (Op) | 2 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cooling System : Corrosion Resistor And Piping
Komatsu : S6d125-1ff(S/N 24781-Up) : Cooling System : Water Pump And Mounting
| 01***30 | Bolt,(For France Noise Suppression) | 2 |
| 01***16 | Bolt (With Air Heater & Conditioner) | 6 |
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 4 |
Cylinder Block
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Block : Camshaft And Tappet
| 01***22 | Bolt | 2 |
| 04***25 | Key, Plain Woodruff | 1 |
| 04***12 | Ring,Snap (For Ripper) | 12 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Block : Crankshaft
| 01***25 | Bolt,(Without Rops Guard? Canopy) | 6 |
| 01***30 | Screw | 1 |
| 01***35 | Screw | 5 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Block : Cylinder Block
| 01***12 | Bolt,(Without Air Compressor Type) | 2 |
| 01***45 | Washer,(For Travel Motor) (Not Show) | 14 |
| 04***14 | Pin, Dowel | 2 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Block : Cylinder Block Cover
| 01***16 | Bolt (With Air Heater & Conditioner) | 1 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 2 |
| 01***00 | Bolt, Mount Back-Up Alarm | 2 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Block : Flywheel And Flywheel Housing
| 01***40 | Bolt,(Dust And Dirt Protection) | 2 |
| 01***50 | Bolt, Radiator To Frame | 6 |
| 01***70 | Bolt - Thrust Plate Mounting | 2 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Block : Front Cover And Front Support
| 01***25 | Bolt,(Without Auto Priming System) | 6 |
| 01***60 | Screw | 1 |
| 01***65 | Bolt,(Except Japan) | 7 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Block : Oil Pan
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 31 |
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 7 |
| 01***16 | Washer,Radio Controlled Slag Handling | 38 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Block : Piston And Connecting Rod
| 02***13 | Pin, Dowel | 2 |
| 04***18 | Ring, Snap | 2 |
| 61***31 | Piston Ring Ass'Y | 6 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Block : Power Take Off (1/2)
| 01***10 | Bolt,(With Auto Emergency Steering) | 4 |
| 01***35 | Bolt, Bolt, Mount Tubes To Switch And Work Pumps | 6 |
| 01***40 | Bolt,(With Service Valve R.H.) | 6 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Block : Power Take Off (2/2)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 4 |
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 4 |
| 01***35 | Bolt,(For Quick Shift) (Mitsubishi) | 4 |
Cylinder Head
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Head : Air Cleaner And Mounting
| 01***40 | Bolt,(Dust And Dirt Protection) | 2 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 8 |
| 01***08 | Nut,(For Straight Tilt Dozer) (D65p) | 6 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Head : Air Intake Manifold And Connection
| 01***10 | Bolt,(With Auto Emergency Steering) | 2 |
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 11 |
| 01***55 | Bolt, Mount Tube To Switch Pump | 5 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Head : Cylinder Head(#24781-25655)
| 04***20 | Pin,Dowel (Welded) | 2 |
| 61***30 | Sleeve,Holder | 1 |
| 61***20 | Cotter, Valve | 48 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Head : Cylinder Head(#25656-)
| 04***20 | Pin,Dowel (Welded) | 2 |
| 61***30 | Sleeve,Holder | 1 |
| 61***20 | Cotter, Valve | 48 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Head : Exhaust Manifold And Turbocharger
| 01***80 | Bolt, Mount Strainer Flange | 2 |
| 01***00 | Bolt (M10-1.50x100) | 16 |
| 01***45 | Screw | 4 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Head : Muffler And Mounting
| 01***40 | Bolt,(Dust And Dirt Protection) | 4 |
| 01***55 | Bolt,(For Suction? Reversible Fan) | 4 |
| 01***30 | Bolt,Radio Controlled Slag Handling | 4 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Head : Rocker Arm And Housing
| 01***08 | Nut,R.H. Thread | 2 |
| 01***16 | Washer,Radio Controlled Slag Handling | 40 |
| 61***10 | Housing, Rocker Lever | 6 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Head : Rocker Arm Housing Cover
| 01***16 | Washer,Radio Controlled Slag Handling | 24 |
| 61***11 | Cover,Head? No.2?3?4?5?6 | 6 |
| 61***10 | Gasket,Cylinder Head Cover | 6 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Head : Turbocharger
| 61***00 | Turbocharger Ass'Y,(Tv7705) | 1 |
| GA***85 | V-Band Ass'Y | 1 |
| GA***07 | Rotor Ass'Y | 1 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Cylinder Head : Water Manifold And Thermostat
| 02***43 | O-Ring,Water Manifold | 6 |
| 07***15 | Plug,(Used When Without Heater) | 1 |
| 08***00 | Sensor,Water Temp. And T/C Oil Temp | 1 |
Electrical System
Komatsu : S6d125-1ff(S/N 24781-Up) : Electrical System : Alternator (13a)
| 60***50 | Alternator A. (13a),(With Non Hardening Pulley) | 1 |
| 60***70 | Alternator A. (13a),(Sandy And Dusty Terrain S.) | 1 |
| KD***31 | Bushing,Insulator | 2 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Electrical System : Alternator (35a) (With Hardening Pulley)
| 60***60 | Alternator A. (35a),(With Non Hardening Pulley) | 1 |
| KD***57 | Bearing,Ball? Front | 1 |
| KD***80 | Collar | 1 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Electrical System : Alternator And Mounting (13a)
| 01***80 | Bolt,(Not Shown) | 1 |
| 01***30 | Bolt | 1 |
| 01***11 | Nut (Welded) | 1 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Electrical System : Alternator And Mounting (35a)
| 01***90 | Bolt, Fan Mounting | 1 |
| 01***30 | Bolt | 1 |
| 01***23 | Washer,(A)(W/After Cooler)(S6d155-4b) | 2 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Electrical System : Starting Motor (11kw)
| 60***11 | Starting Motor Ass'Y,(11kw)(See Fig.0662) | 1 |
| SD***X9 | Bracket,Rear | 1 |
| SD***X9 | Metal | 1 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Electrical System : Starting Motor (7.5kw)
| 60***30 | Starting Motor Ass'Y,(7.5kw) | 1 |
| KD***60 | Shift Lever Assembly | 1 |
| KD***40 | Spring,Spring | 4 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Electrical System : Starting Motor And Mounting (7.5kw? 11kw)
| 01***40 | Bolt,(With Center Guard) | 3 |
| 66***10 | Gasket,Starting Motor | 1 |
| (6***0) | Starting Motor Ass'Y,(7.5kw) (See Fig.0661a) | 1 |
Engine Kit
Komatsu : S6d125-1ff(S/N 24781-Up) : Engine Kit : Gasket Kit
| 01***23 | Washer,Lock (K5) | 1 |
| 02***43 | O-Ring,Water Manifold | 6 |
| 06***03 | Seal,Bearing (K2) | 2 |
Fuel System
Komatsu : S6d125-1ff(S/N 24781-Up) : Fuel System : Fuel Control Lever
| 01***20 | Screw | 3 |
| 01***06 | Nut,(With Back-Up Alarm) (Op), Nut; Was 01580-10806 | 3 |
| 01***09 | Nut (Itl) | 1 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Fuel System : Fuel Filter And Piping
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 2 |
| 01***16 | Washer,Radio Controlled Slag Handling | 2 |
| 07***12 | Gasket,Mechanical Pump Piping | 2 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Fuel System : Fuel Injection Pump (Coupling)
| 61***32 | Injection Pump A.,(See Fig.0451) | 1 |
| DK***00 | Coupling,Cross | 1 |
| DK***60 | Coupling Ass'Y | 1 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Fuel System : Fuel Injection Pump (Feed Pump)
| 61***32 | Injection Pump A.,(See Fig.0451) | 1 |
| DK***20 | Bolt, Joint | 1 |
| DK***00 | Valve,Check | 2 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Fuel System : Fuel Injection Pump (Governor) (1/2)
| 61***32 | Injection Pump A.,(See Fig.0451) | 1 |
| DK***20 | Flyweight Ass'Y | 1 |
| DK***20 | Guide Lever Ass'Y | 1 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Fuel System : Fuel Injection Pump (Governor) (2/2)
| 61***32 | Injection Pump A.,(See Fig.0451) | 1 |
| DK***00 | Nut,Cap | 1 |
| DK***00 | Cover | 1 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Fuel System : Fuel Injection Pump (Pump)
| 61***32 | Injection Pump A.,(See Fig.0451) | 1 |
| 61***33 | Injection Pump A | 1 |
| DK***30 | Bearing,Roller | 2 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Fuel System : Fuel Injection Pump And Piping
| 01***30 | Bolt | 1 |
| 01***20 | Bolt,(For Quick Shift) (Mitsubishi) | 2 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 4 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Fuel System : Fuel Nozzle And Spill Tube
| 01***45 | Bolt, Divider Valve Mounting | 12 |
| 07***65 | O-Ring,Cylinder Block | 6 |
| 07***12 | Gasket,Mechanical Pump Piping | 2 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Fuel System : Water Separator And Mounting
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 1 |
| 01***40 | Bolt, Mount Master Brake Cylinder | 1 |
| 01***50 | Bolt,(With Service Valve R.H.) | 1 |
Lubricating Oil System
Komatsu : S6d125-1ff(S/N 24781-Up) : Lubricating Oil System : Lubricating Oil Cooler
| 01***25 | Bolt,Without Revolution Sensor | 2 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 12 |
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 1 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Lubricating Oil System : Lubricating Oil Filter And Mounting
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 4 |
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 4 |
| 02***16 | Plug | 1 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Lubricating Oil System : Lubricating Oil Piping
| 01***60 | Bolt, Mount Tube To Switch Pump | 2 |
| 01***16 | Washer,Radio Controlled Slag Handling | 7 |
| 04***12 | Ring, Snap | 1 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Lubricating Oil System : Lubricating Oil Pump And Suction Pipe
| 01***25 | Bolt,(Without Auto Priming System) | 4 |
| 01***20 | Bolt,(Large Capacity Type) (Std) | 2 |
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 5 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Lubricating Oil System : Main Clutch Cooler
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 2 |
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 3 |
| 01***40 | Bolt, Mount Master Brake Cylinder | 3 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Lubricating Oil System : Power Take Off Lubricating Oil Piping
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 2 |
| 01***40 | Bolt,(With Service Valve R.H.) | 1 |
| 07***12 | Gasket,(Without Air Compressor Type) (K2) | 23 |
Komatsu : S6d125-1ff(S/N 24781-Up) : Lubricating Oil System : Turbocharger Lubricating Oil Piping
| 01***16 | Bolt, Battery To Frame Ground Wire Attaching | 2 |
| 01***20 | Bolt,(For Quick Shift) (Mitsubishi) | 2 |
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 2 |
S6D125-1FF(S/N 24781-UP) serial number reference
The engine serial number plate is typically stamped on the engine block, usually on the left side near the injection pump. The prefix is part of the engine model code (S6D125-1FF) found on this plate, not a separate 3-character PIN prefix for the engine itself. The machine's 17-character ISO PIN (if equipped) is located on the emissions/export plate, typically near the engine bay or cab pillar.
| Prefix | Identifies | Notes |
|---|---|---|
| S6D125-1FF | Engine model | Komatsu S6D125-1FF engine family. Serial range 24781-UP. Confirmed by Komatsu parts catalog and DK Engine Parts guide. No specific 3-character PIN prefix (e.g., KMT) is listed in the provided source text for this engine serial range; the source text only provides the engine model code and serial break. Confirm with dealer for specific 17-character ISO PIN prefixes associated with this engine serial range. |
Frequently asked questions
What is the engine type and displacement?
The Komatsu S6D125-1FF is a 6-cylinder, 11-liter diesel engine, available in turbocharged and aftercooled configurations.
What is the operating weight range for machines using this engine?
Operating weight varies by configuration and series, typically ranging from 24,000 kg to over 80,000 kg depending on the host machine model and attachment package.
What engine replaced the S6D125-1FF?
The S6D125E-2 series engine succeeded the S6D125-1FF, offering updated emissions compliance and electronic control features.
What S6D125-1FF(S/N 24781-UP) owners discuss
What are the known powertrain and hydraulic behaviors for the Komatsu S6D125-1FF engine series?
What undercarriage or wear patterns are typical for machines powered by this engine series?
What are the specific engine quirks and maintenance requirements for the S6D125-1FF series?
What are the common electrical and sensor issues reported for this engine?
What should be checked when buying a used machine with the S6D125-1FF (S/N 24781-UP)?
What are the recommended fluid specifications for the S6D125-1FF engine and related systems?
What safety-critical fix is associated with the wet liner design of this engine?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
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