Komatsuengine(no series)
Komatsu 6D125E-2A-40(S/N 61779-UP)
Maintenance schedule, common problems & OEM parts breakdown
The 6D125E-2A-40(S/N 61779-UP) is the naturally aspirated version of Komatsu's 125-series inline-six diesel, built specifically for the D65E-12 crawler dozer, a mid-size dozer class machine. It produces roughly 142 kW (190 hp) at 1950 rpm from 11.04 L (673.8 cu in) of displacement, mechanically governed with no turbocharger or electronic engine controls, and drives the machine through a TORQFLOW torque converter and powershift transmission. Depending on blade, ripper, and dash-configuration, the host dozer's operating weight runs roughly 14,870-19,125 kg (32,780-42,160 lb). This D65-12 generation dozer was produced through the 1990s into the early 2000s, following the earlier D65-8 series and preceding the turbocharged, electronically assisted D65EX-15/D65PX-15 generation. Komatsu offered this platform in standard-gauge E/EX straight-tilt-blade form and wide-gauge, low-ground-pressure P/PX swamp configurations, with the naturally aspirated 6D125E-2A fitted to the base E variant and the turbocharged S6D125E-2 fitted to the EX/PX siblings.
Within the D65-12 family, the main split is aspiration and output: this naturally aspirated 'A' spec engine on the base D65E/D65P chassis versus the turbocharged S6D125E-2 on the higher-output EX/PX variants, sharing the same block, bore, and stroke but different breathing and power ratings. The next generation dropped the mechanical fuel system and flyweight governor for electronically controlled, turbo-aftercooled engines and a redesigned cab, moving away from the simple analog gauge panel this engine relies on. That simplicity is exactly why this generation still holds value in the parts and rebuild market: no ECM or wiring harness to fail, straightforward diagnosis with warning lamps instead of fault codes, and a mechanically durable block that shops can overhaul rather than replace outright. Buyers shopping this era weigh undercarriage and torque converter condition heavily, since those wear items, not the engine, usually decide a used machine's price.
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 6D125E-2A-40(S/N 61779-UP) specifications
Engine
| Model | Komatsu 6D125E-2-A, naturally aspirated spec introduced at this serial break (turbocharged S6D125E-2 covers the wider-gauge sister configuration) |
| Gross power | 142 kW (190 hp) at 1950 rpm, flywheel |
| Displacement | 11.04 L (673.8 cu in) |
| Cylinders | 6, inline, bore 125 mm (4.92 in) x stroke 150 mm (5.91 in) |
| Aspiration | Naturally aspirated, water-cooled 4-stroke direct injection |
Weights
| Operating weight | Varies by configuration/series: approx. 14,870-19,125 kg (32,780-42,160 lb) depending on blade, ripper, and dash-suffix variant fitted to the host dozer |
Dimensions
| Length with blade | approx. 5.26 m (17.26 ft) |
| Length without blade | approx. 4.37 m (14.34 ft) |
| Width over tracks | 2.39 m (7.85 ft) |
| Height to cab top | approx. 3.06 m (10.03 ft) |
| Track gauge | 1.88 m (6.17 ft) |
| Ground clearance | approx. 0.41 m (1.33 ft) |
| Length of track on ground | 2.68 m (8.78 ft) |
Performance
| Max forward travel speed | 10.6 km/h (6.6 mph), top gear |
| Max reverse travel speed | 13.4 km/h (8.3 mph), top gear |
| Transmission | Torque converter powershift, 3 forward / 3 reverse gears |
Service capacities (summary)
| Fuel tank | 406 L (107.3 US gal) |
| Cooling system | 52 L (13.7 US gal) |
| Engine oil | 38 L (10.0 US gal) |
| Hydraulic system | 55 L (14.5 US gal) |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
6D125E-2A-40(S/N 61779-UP) fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Engine crankcase (with filter) | 38 L (10.0 US gal) | Komatsu Genuine diesel engine oil, EO10W30 or EO15W40 grade selected by ambient air temperature at startup per the OMM viscosity chart (roughly -30 deg C to +50 deg C range, 10W30 for colder end, 15W40 for warmer end); meets Komatsu EO engine-oil classification comparable to API CD/CF-4 duty. |
| Cooling system | 52 L (13.7 US gal) | Komatsu Genuine Supercoolant / Antifreeze Coolant AF-NAC, ethylene-glycol based, factory pre-mixed to a 50/50 ratio; change interval per OMM is 2 years or 4,000 hours, whichever comes first. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Komatsu 6D125E-2A-40(S/N 61779-UP) maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 50 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
| Every 4,000 h |
|
Servicing the 6D125E-2A-40(S/N 61779-UP) beyond the schedule
Predictive Maintenance & Fluid Analysis
Pull engine oil and coolant samples on schedule rather than by feel. This 125-series naturally aspirated block has a known weep point between coolant and oil circuits, so cross-contamination shows up in lab analysis before it shows on a dipstick. Watch torque converter temperature under load; a slow climb with no external leak points to an internal forward-clutch bypass, not a cooling-system fault. Track undercarriage wear (bushing, sprocket segment, shoe height) against OEM minimums each service interval, since undercarriage cost typically outpaces engine cost over the machine's life.
Corrective & Common Repairs
Oil showing up in coolant on this block usually traces to the oil cooler core, not a cracked head; pressure-test before committing to a gasket job. Torque converter overheating without an external leak is commonly a forward-clutch internal seal letting oil bypass the cooler, not a radiator fault. Weeping around the belly pan is typically a steering clutch or brake seal, hydraulic line, or pump gasket, not the engine itself. Dash and gauge dropouts trace to blown fuses, corroded connectors, or weak grounds behind the panel, not a failed sensor.
Overhaul & Rebuild Points
This naturally aspirated 125-series block is mechanically governed with no turbo or electronic controls, making it a straightforward rebuild candidate compared to later electronic engines. Resurface the head if a coolant weep has been running long enough to erode the surface; check the block for warpage after any overheating event. Match piston rings and liners to factory spec; mismatched aftermarket sets are a common cause of wear inside months, not years. On the undercarriage, segment-style sprockets let a shop renew worn tooth sections without pulling the whole final drive.
Seasonal & Environment Servicing
Select engine oil viscosity by ambient startup temperature per the OMM chart; run the lighter grade through cold snaps and the heavier grade once temperatures climb. Confirm the intake air heater and preheat lamp work before winter; a mechanically governed engine with no electronic cold-start assist depends on that circuit for starts. Keep coolant at the factory antifreeze concentration for freeze protection, not just topped with water. In hot, dusty conditions, clean radiator fins often and check track tension more frequently, since heat and abrasive ground both accelerate undercarriage wear.
6D125E-2A-40(S/N 61779-UP) common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| 07281-00197 | Clamp,(With Pre-Fuel Filter) | Fuel system service | Check fitment → |
| 600-311-8283 | Cartridge,Fuel Filter | Fuel system service | Check fitment → |
| 600-311-8331 | Cartridge,Fuel Filter | Fuel system service | Check fitment → |
| 6150-72-6600 | Fuel Filter Ass'Y | Fuel system service | Check fitment → |
| 6150-72-6601 | Fuel Filter Ass'Y | Fuel system service | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
6D125E-2A-40(S/N 61779-UP) fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| Engine Oil Pressure Warning Lamp (red) | Engine oil pressure has dropped below the safe minimum threshold. | Low oil level, clogged oil filter, worn oil pump, or a failed pressure sender. | Stop the engine immediately. Check oil level and inspect for leaks before restarting. |
| Coolant Temperature Warning Lamp (red) | Engine coolant temperature has exceeded the safe operating range. | Low coolant level, clogged radiator core, slipping or broken fan belt, or a stuck thermostat. | Reduce load, idle down, and shut down safely. Let the engine cool before checking coolant level and radiator condition. |
| Charge (Generator) Warning Lamp | Alternator is not charging the battery. | Broken or slipping fan/alternator belt, failed alternator, or a loose wiring connection. | Check belt tension and alternator output; inspect wiring and battery terminals. |
| Preheat (Intake Air Heater) Indicator Lamp | Intake air preheating cycle is active to assist cold starting. | Normal cold-start operation; not a fault unless the lamp stays on abnormally long or fails to illuminate in cold weather. | Wait for the lamp to go out before cranking. If it never illuminates when cold, check the preheat circuit. |
| Air Cleaner Restriction Indicator | Intake air filter restriction has reached the service limit. | Dirty or clogged air filter element. | Service or replace the air filter element and reset the restriction indicator. |
| Fuel Level Warning Lamp | Fuel tank level is low. | Tank running low in normal operation, or an unexpected fuel leak. | Refuel. If the level drops faster than expected, check fuel lines and tank for leaks. |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
6D125E-2A-40(S/N 61779-UP) attachments & work tools
Product type note
This is a bare diesel engine long block (Komatsu 125-series, naturally aspirated 6D125E-2 family), not a complete machine. It has no coupler-mounted work-tool line; the entries below cover factory drive, cooling, and mounting configuration instead of implement attachments.
Aspiration / exhaust configuration
The 6D125E-2A designation (no leading S) is the naturally aspirated version of the 125-series block, distinct from the turbocharged S6D125E-2 and turbo-aftercooled SA6D125E-2/SAA6D125E siblings built on the same bore and stroke. Exhaust routes through a dry manifold to the host machine's muffler; the NA build has no charge-air/aftercooler plumbing.
Flywheel housing / power-train mounting
The engine mates to the host machine's power train through an SAE-pattern flywheel housing rather than a stationary industrial PTO clutch. On its dozer applications this bolts directly to a Komatsu TORQFLOW torque converter and planetary-clutch transmission; housing size and bolt pattern vary by host machine, so treat as varies by configuration/series.
Accessory & hydraulic pump drive
Engine-driven pads at the front and rear of the block carry the belt-driven alternator/fan and a gear- or shaft-driven hydraulic pump feeding the machine's implement and steering circuits. Exact pump count and drive ratio depend on which host machine the arrangement number was built for.
Cooling / radiator arrangement
Standard build uses an engine-driven blower fan pushing air through a front-mounted radiator supplied by the host machine, water-cooled block and jacket per Komatsu's TORQFLOW-era dozer cooling layout. No remote/keel-cooled or heat-exchanger variant is documented for this engine family; it is built for direct radiator mounting.
Factory arrangement / application variants
Komatsu issued this long block under multiple factory arrangement (spec) numbers - letters after the series digit (A/D/G-type suffixes) plus trailing index numbers - each matched to a specific host machine's mounting brackets, accessory drive, and cooling hardware. Published cross-reference for every individual suffix is not public; power class for the naturally aspirated 125-series in this serial range runs roughly 130-140 kW (175-190 hp) class, varies by configuration/series and host machine.
Guarding / engine-compartment shielding
Fan and drive-belt guarding is supplied as part of the host machine's engine compartment sheet metal rather than as an aftermarket engine accessory kit. No standalone guard package is documented for this engine model on its own.
All 6D125E-2A-40(S/N 61779-UP) assemblies by section
Every catalogued assembly group for the Komatsu 6D125E-2A-40(S/N 61779-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Engine
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Air Cleaner (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***40 | Capscrew | 1 |
| 01***08 | Nut,(For Straight Tilt Dozer) (D65p) | 6 |
| 01***16 | Washer,Radio Controlled Slag Handling | 6 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Air Cleaner Cap(#69524-80454)
| 08***10 | Tie, Cable | 1 |
| 56***00 | Cap,(With Weather Cap Type) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Air Cleaner Cap(#80455-)
| 08***10 | Tie, Cable | 1 |
| 56***00 | Cap,(With Weather Cap Type) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Air Intake Manifold
| 01***30 | Bolt,(With Body Positioner) | 10 |
| 01***55 | Bolt,(See Service News) | 4 |
| 01***05 | Capscrew | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Air Vent (Cold Terrain Spec.) (-40?C)(#69524-)
| 07***12 | Gasket,(Without Air Compressor Type) (K2) | 12 |
| 07***10 | Screw, Banjo Connector (M10-1.25x20) | 6 |
| 61***60 | Tube,Air Vent | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Air Vent(#75278-)
| 07***12 | Gasket,(Without Air Compressor Type) (K2) | 12 |
| 07***10 | Screw, Banjo Connector (M10-1.25x20) | 6 |
| 61***60 | Tube,Air Vent | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Alternater (35a) (With Non Hardening Pulley) (Cold Terrain Spec.)(-40?C) (Inner Parts)(#69524-)
| 60***50 | Alternator A. (35a) | 1 |
| KD***70 | Bushing,Insulate | 1 |
| KD***40 | Bushing,Insulate | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Alternater Mounting (35a) (With Non Hardening Pully) (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***45 | Bolt,(With Water Separator Type) | 2 |
| 01***55 | Bolt - Mount Cage To Transmission Case | 1 |
| 01***55 | Bolt | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Camfollower Cover(#69524-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 2 |
| 01***00 | Bolt,(For Front Brake Release) | 2 |
| 01***08 | Nut,(For Canvas Canopy?Head Guard) | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Camshaft (Mechanical Governor Spec.)
| 01***22 | Capscrew | 2 |
| 04***25 | Key, Plain Woodruff | 1 |
| 04***12 | Ring,Snap (For Ripper) | 12 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Camshaft(#61779-76795)
| 01***22 | Capscrew | 2 |
| 04***25 | Key, Plain Woodruff | 1 |
| 04***12 | Ring,Snap (For Ripper) | 12 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Caution Plate (English)(#80455-)
| 09***08 | Plate? Instruction,Air Cleaner | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Cooling Fan (Reversible Fan) (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***30 | Bolt,(With Body Positioner) | 6 |
| 01***40 | Bolt (Op) | 6 |
| 60***50 | Fan,Reversible | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Corrosion Resistor (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***16 | Bolt, Battery To Frame Ground Wire Attaching | 2 |
| 01***20 | Bolt,(For Mono Lever Steering) | 3 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Crank Pulley (Non Hardening Pulley)
| 01***30 | Screw | 1 |
| 01***35 | Screw | 5 |
| 04***28 | Pin, Dowel - Transmission Case, Pin-Dowel | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Crankshaft(#67074-)
| 61***10 | Bearing, Main (Standard) | 7 |
| 61***50 | Bearing, Thrust Assembly (Standard) | 1 |
| 61***10 | Bearing, Main (1.00mm Undersize) | 7 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Cylinder Block (1/2) (Cold Terrain Spec.) (-40?C)(#69524-76885)
| 01***12 | Bolt,(Without Air Compressor Type) | 2 |
| 01***45 | Washer,(For Travel Motor) (Not Show) | 14 |
| 04***14 | Pin, Dowel | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Cylinder Block (2/2) (Cold Terrain Spec.) (-40?C)(#69524-76885)
| 01***20 | Bolt,(For Mono Lever Steering) | 4 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 5 |
| 07***15 | Plug,(For Without Air Compressor) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Cylinder Block (High Altitude Spec.)(#76796-)
| 01***12 | Bolt,(Without Air Compressor Type) | 2 |
| 01***45 | Washer,(For Travel Motor) (Not Show) | 14 |
| 04***14 | Pin, Dowel | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Cylinder Block (High Altitude Spec.)(#76886-)
| 01***12 | Bolt,(Without Air Compressor Type) | 2 |
| 01***20 | Bolt,(For Shipping) | 1 |
| 01***16 | Bolt, Mount Solenoid Valve | 6 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Cylinder Block Blind Cover And Plug (Coolant Heater Spec.)(#76886-)
| 01***20 | Bolt,(For Mono Lever Steering) | 4 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 5 |
| 01***12 | Bolt,(Without Air Compressor Type) | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Cylinder Block Blind Cover And Plug (Extreme Cold Terrain Spec.)(#76886-)
| 01***20 | Bolt,(For Mono Lever Steering) | 4 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 5 |
| 01***12 | Bolt,(Without Air Compressor Type) | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Cylinder Block Blind Cover And Plug (High Altitude Spec.)(#76886-)
| 01***20 | Bolt,(For Mono Lever Steering) | 5 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 5 |
| 01***12 | Bolt,(Without Air Compressor Type) | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Cylinder Block Blind Cover And Plug(#76886-)
| 01***20 | Bolt,(For Mono Lever Steering) | 4 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 5 |
| 01***12 | Bolt,(Without Air Compressor Type) | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Cylinder Block Gasket Kit(#69524-)
| 07***21 | O-Ring,Water Piping | 1 |
| 07***30 | Ring, Seal - Between Sections | 2 |
| 07***15 | O-Ring,Relief Valve | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Cylinder Head Gasket Kit(#69524-)
| 07***65 | O-Ring,Cylinder Block | 6 |
| 07***12 | Gasket,Mechanical Pump Piping | 15 |
| 07***12 | Gasket,(Without Air Compressor Type) (K2) | 24 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Cylinder Head(#67992-)
| 01***20 | Bolt (M10-1.75x120) | 6 |
| 04***20 | Pin,Dowel (Welded) | 2 |
| 07***08 | Plug,(Without Lock-Up), Plug | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Damper
| 01***25 | Bolt,(Without Rops Guard? Canopy) | 6 |
| 61***00 | Damper Assembly | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Engine Mounting
| 01***50 | Bolt,(Spark Arrester Spec.) | 2 |
| 01***05 | Capscrew | 4 |
| 01***10 | Bolt,(With Joy Stick Steering) | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Exhaust Manifold (Extreme Cold Terrain Spec.)(#78098-)
| 01***40 | Bolt, Mount Master Brake Cylinder | 1 |
| 01***80 | Screw | 12 |
| 01***85 | Bolt | 6 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Exhaust Manifold (High Altitude Spec.) (With Safety Cover)(#79153-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 4 |
| 01***50 | Bolt,(Spark Arrester Spec.) | 2 |
| 01***70 | Bolt - Bracket And Oil Inlet Tubemounting | 6 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Exhaust Manifold (With Cover) (For Japan) (High Altitude Spec.)(#79153-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 4 |
| 01***50 | Bolt,(Spark Arrester Spec.) | 2 |
| 01***70 | Bolt - Bracket And Oil Inlet Tubemounting | 6 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Exhaust Manifold (With Safety Cover)(#61779-79152)
| 01***20 | Bolt,(For Mono Lever Steering) | 2 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 6 |
| 01***95 | Capscrew | 6 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Exhaust Manifold (With Safety Cover)(#79153-)
| 01***20 | Bolt,(For Mono Lever Steering) | 2 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 6 |
| 01***95 | Capscrew | 6 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Exhaust Pipe (Black Exhaust Pipe? 660mm)(#80455-)
| 61***40 | Pipe,Exhaust | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fan Drive(#69524-)
| 01***65 | Bolt - Return Line And Suction Linehose Clamps | 4 |
| 01***14 | Nut,(For Slag Handling) | 1 |
| 01***16 | Washer,(With Water Separator) | 4 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fan Guard (1/2)(#69524-)
| 01***30 | Bolt,(With Body Positioner) | 2 |
| 01***40 | Bolt (Op) | 2 |
| 01***70 | Bolt - Bracket And Oil Inlet Tubemounting | 4 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fan Guard (2/2)(#69524-)
| 01***30 | Bolt,(With Body Positioner) | 1 |
| 01***35 | Bolt,(F4320-52a0 -5 ) | 5 |
| 01***45 | Bolt,(With Water Separator Type) | 7 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fan Pulley (Non Hardening Pulley) (Cold Terrain Spec.) (-40?C)(#69524-)
| 04***71 | V-Belt Set | 1 |
| 61***21 | Pulley?Non Hardening,Non Hardening | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Flywheel
| 01***55 | Bolt | 6 |
| 01***45 | Washer,(For Travel Motor) (Not Show) | 6 |
| 06***08 | Bearing, Ball | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Flywheel Housing
| 01***60 | Bolt, Hanger Bearing Mounting | 2 |
| 01***60 | Bolt,(For Ripper) | 2 |
| 01***50 | Capscrew | 6 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Front Cover (Noise Suppression Spec.)(#61779-76885)
| 01***65 | Bolt - Return Line And Suction Linehose Clamps | 8 |
| 01***75 | Bolt (M10-1.50x75) | 4 |
| 09***50 | Liquid Gasket, Lg-7, 150g | 0 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Front Cover Mounting (Noise Suppression Spec.)(#76886-)
| 01***65 | Bolt - Return Line And Suction Linehose Clamps | 8 |
| 01***75 | Bolt (M10-1.50x75) | 4 |
| 61***40 | Indicator | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Front Cover Mounting(#76886-)
| 01***65 | Bolt - Return Line And Suction Linehose Clamps | 8 |
| 01***70 | Bolt - Bracket And Oil Inlet Tubemounting | 4 |
| 01***75 | Bolt (M10-1.50x75) | 6 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Front Cover(#76886-)
| 09***50 | Liquid Gasket, Lg-7, 150g | 0 |
| 61***30 | Seal? Front (K2) | 1 |
| 61***40 | Cover,Front | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fuel Filter (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 7 |
| 01***05 | Capscrew | 1 |
| 01***20 | Capscrew | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fuel Injection Pump (Coupling) (Cold Terrain Spec.) (-40?C) (Inner Parts)(#69524-)
| ND***10 | Flange,Coupling | 1 |
| ND***50 | Bolt | 1 |
| ND***40 | Bolt | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fuel Injection Pump (Feed Pump) (Cold Terrain Spec.) (-40?C) (Inner Parts)(#69524-)
| ND***40 | Washer? 1mm,Plate | 1 |
| ND***00 | Seal,Oil | 1 |
| ND***10 | Spring, Check Valve | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fuel Injection Pump (Governor) (1/2) (Cold Terrain Spec.) (-40?C) (Inner Parts)(#69524-)
| ND***40 | Plate,Thrust | 1 |
| ND***40 | Plug,Screw | 1 |
| ND***10 | Adapter | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fuel Injection Pump (Governor) (2/2) (Cold Terrain Spec.) (-40?C) (Inner Parts)(#69524-)
| ND***70 | Arm,Spring | 1 |
| ND***20 | Washer? 1.0mm,Cover Plate | 2 |
| ND***20 | Cover | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fuel Injection Pump (Pump) (1/2) (Cold Terrain Spec.) (-40?C) (Inner Parts)(#69524-)
| 61***70 | Injection Pump Ass'Y | 1 |
| ND***80 | Bearing,Center | 1 |
| ND***50 | Ring,Adjust | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fuel Injection Pump (Pump) (2/2) (Cold Terrain Spec.) (-40?C) (Inner Parts)(#69524-)
| ND***60 | Element,Pump | 6 |
| ND***11 | Shim? 1.7mm | 0 |
| ND***30 | Washer? 0.3mm | 0 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fuel Injection Pump Drive (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 4 |
| 01***14 | Nut (Itl) | 1 |
| 01***60 | Washer,(Without Rops Guard? Canopy) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fuel Injection Pump Mounting (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***75 | Capscrew | 4 |
| 61***10 | Washer,Spring | 4 |
| (6***0) | Injection Pump Ass'Y,(See Fig.A4010-B3n4) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fuel Injection Pump Piping (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***30 | Screw | 4 |
| 01***55 | Bolt,(See Service News) | 4 |
| 01***70 | Bolt - Bracket And Oil Inlet Tubemounting | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fuel Injection Pump Piping (High Altitude Spec.)(#80455-)
| 01***30 | Screw | 4 |
| 01***55 | Bolt,(See Service News) | 4 |
| 01***70 | Bolt - Bracket And Oil Inlet Tubemounting | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Fuel Return
| 01***20 | Bolt,(For Mono Lever Steering) | 1 |
| 01***60 | Bolt,(F4320-52a0 -5- ) | 1 |
| 01***70 | Bolt - Bracket And Oil Inlet Tubemounting | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Head Cover (Cold Terrain Spec.) (-40?C)(#69524-)
| 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 : 6d125e-2a-40(S/N 61779-Up) : Engine : Heater Switch (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***16 | Bolt - Box Mounting | 2 |
| 01***55 | Bolt,(See Service News) | 1 |
| 01***10 | Washer,(For 35a Alternator) | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Idler Gear
| 01***60 | Screw | 1 |
| 01***60 | Capscrew | 1 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 6 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Injection Nozzle (High Altitude Spec.)(#81895-)
| 01***45 | Bolt, Mount Divider Valve | 12 |
| 07***65 | O-Ring,Cylinder Block | 6 |
| 07***12 | Gasket,Mechanical Pump Piping | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Injection Nozzle(#61779-81894)
| 01***45 | Bolt, Mount Divider Valve | 12 |
| 07***65 | O-Ring,Cylinder Block | 6 |
| 07***12 | Gasket,(Without Air Compressor Type) (K2) | 12 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Injection Nozzle(#81895-)
| 01***45 | Bolt, Mount Divider Valve | 12 |
| 07***65 | O-Ring,Cylinder Block | 6 |
| 07***12 | Gasket,(Without Air Compressor Type) (K2) | 12 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Muffler (Cold Terrain Spec.) (-40?C)(#65397-81894)
| 01***20 | Bolt,(For Mono Lever Steering) | 1 |
| 01***40 | Bolt (Op) | 4 |
| 01***45 | Bolt,(With Water Separator Type) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Muffler (With Cover)(#81895-)
| 01***20 | Bolt,(For Mono Lever Steering) | 1 |
| 01***40 | Bolt (Op) | 4 |
| 01***45 | Bolt,(With Water Separator Type) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Muffler(#81895-)
| 01***20 | Bolt,(For Mono Lever Steering) | 1 |
| 01***40 | Bolt (Op) | 4 |
| 01***45 | Bolt,(With Water Separator Type) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Name Plate And Caution (Arabic-English)(#63405-81894)
| 09***07 | Plate? Instruction,Air Cleaner | 1 |
| 09***08 | Plate? Instruction,Air Cleaner | 1 |
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Name Plate And Caution (Chinese)(#63405-81894)
| 09***07 | Plate? Instruction,Air Cleaner | 1 |
| 09***08 | Plate? Instruction,Air Cleaner | 1 |
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Name Plate And Caution (French-English)(#63405-81894)
| 09***07 | Plate? Instruction,Air Cleaner | 1 |
| 09***08 | Plate? Instruction,Air Cleaner | 1 |
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Name Plate And Caution (German-English)(#63405-81894)
| 09***07 | Plate? Instruction,Air Cleaner | 1 |
| 09***08 | Plate? Instruction,Air Cleaner | 1 |
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Name Plate And Caution (Indonesian-English)(#63405-81894)
| 09***07 | Plate? Instruction,Air Cleaner | 1 |
| 09***08 | Plate? Instruction,(Indonesian) | 1 |
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Name Plate And Caution (Persian-English)(#63405-81894)
| 09***07 | Plate? Instruction,Air Cleaner | 1 |
| 09***08 | Plate? Instruction,Air Cleaner | 1 |
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Name Plate And Caution (Russian)(#69524-81894)
| 09***08 | Plate? Instruction,Air Cleaner | 1 |
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
| 61***10 | Plate? Name,(Russian) (Limited Supply) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Name Plate And Caution (Spanish-English)(#63405-81894)
| 09***07 | Plate? Instruction,Air Cleaner | 1 |
| 09***08 | Plate? Instruction,Air Cleaner | 1 |
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Name Plate And Caution(#81895-)
| 60***10 | Plate | 1 |
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Name Plate And Caution(#84623-)
| 04***50 | Screw | 4 |
| 60***20 | Plate | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Name Plate And Caution(#86280-)
| 60***10 | Plate | 1 |
| 60***80 | Plate | 1 |
| 60***40 | Plate? Name,Engine (Limited Supply) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Nozzle Holder (Inner Parts)(#61779-81894)
| 07***12 | Gasket,Mechanical Pump Piping | 2 |
| 61***10 | Holder Ass'Y | 1 |
| ND***90 | Connector,Inlet | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Nozzle Holder (Inner Parts)(#81895-)
| 07***12 | Gasket,Mechanical Pump Piping | 2 |
| 61***10 | Holder Ass'Y | 1 |
| ND***90 | Connector,Inlet | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Adapter (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***30 | Bolt,(With Body Positioner) | 3 |
| 01***35 | Bolt,(F4320-52a0 -5 ) | 1 |
| 01***50 | Bolt,(Spark Arrester Spec.) | 4 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Cooler (Cold Terrain Spec.) (-40?C)(#69524-76885)
| 01***25 | Bolt,(Rear Attachment Less) | 2 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 13 |
| 01***65 | Bolt - Return Line And Suction Linehose Clamps | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Cooler (Cold Terrain Spec.) (-40?C)(#76886-)
| 01***25 | Bolt - Relay Mounting | 2 |
| 07***42 | O-Ring,(See Fig.A3310) | 1 |
| 07***34 | O-Ring,(F3300-61a0 -5 ) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Cooler (High Altitude Spec.)(#76886-)
| 01***25 | Bolt - Relay Mounting | 2 |
| 07***42 | O-Ring,(See Fig.A3310) | 1 |
| 61***25 | Cover | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Cooler Mounting Parts (Extreme Cold Terrain Spec.)(#76796-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 13 |
| 01***65 | Bolt - Return Line And Suction Linehose Clamps | 2 |
| 01***80 | Bolt,(With Corrosion Resistor) | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Cooler Mounting Parts (High Altitude Spec.)(#76886-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 12 |
| 01***65 | Bolt - Return Line And Suction Linehose Clamps | 2 |
| 01***80 | Bolt,(With Corrosion Resistor) | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Cooler(#76796-)
| 01***25 | Bolt - Relay Mounting | 2 |
| 07***42 | O-Ring,(See Fig.A3310) | 1 |
| 61***11 | Element | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Filter (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 3 |
| 01***30 | Capscrew (1) | 4 |
| 07***35 | O-Ring,Transmission Valve Mount | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Level Gauge
| 01***16 | Bolt - Seat And Tether Belt Mounting | 1 |
| 01***06 | Nut,(With Back-Up Alarm) (Op), Nut; Was 01580-10806 | 1 |
| 01***10 | Washer,See Fig. K4010-12a0 | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Level Gauge (Extreme Cold Terrain Spec.)(#78098-)
| 01***16 | Bolt - Seat And Tether Belt Mounting | 1 |
| 01***06 | Nut,(With Back-Up Alarm) (Op), Nut; Was 01580-10806 | 1 |
| 01***10 | Washer,See Fig. K4010-12a0 | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Pan And Suction Tube
| 01***20 | Bolt,(For Mono Lever Steering) | 1 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 31 |
| 01***30 | Bolt,(With Body Positioner) | 6 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Pan And Suction Tube (Extreme Cold Terrain Spec.)(#78098-)
| 01***12 | Bolt - Front Cover Mounting | 3 |
| 01***20 | Bolt,(For Mono Lever Steering) | 1 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 31 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Oil Pump (High Altitude Spec.) (Cold Terain Spec.) (-40?C)
| 01***25 | Bolt,(Rear Attachment Less) | 4 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 3 |
| 01***35 | Bolt,(F4320-52a0 -5 ) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Piston (Cold Terrain Spec.) (-40?C)(#69524-)
| 02***13 | Pin, Dowel | 2 |
| 04***18 | Ring, Snap | 12 |
| 61***10 | Pin,Piston | 6 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Rocker Arm (Mechanical Governor Spec.)
| 01***75 | Screw | 40 |
| 01***08 | Nut,R.H. Thread | 2 |
| 01***32 | Washer,(With Auto Emergency Steering) | 40 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Rocker Arm(#61779-76795)
| 01***75 | Screw | 40 |
| 01***08 | Nut,R.H. Thread | 12 |
| 01***32 | Washer,(With Auto Emergency Steering) | 40 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Safety Guard (For Fuel Injection Pump Drive)
| 01***20 | Bolt,(For Mono Lever Steering) | 2 |
| 61***50 | Cover, Safety | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Spare Parts (Cold Terrain Spec.) (-40?C)(#69524-80454)
| 04***71 | V-Belt Set | 1 |
| 07***34 | O-Ring,Transmission And Steering Case | 1 |
| 07***12 | Gasket,Mechanical Pump Piping | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Spare Parts (Cold Terrain Spec.) (-40?C)(#80455-)
| 04***71 | V-Belt Set | 1 |
| 07***34 | O-Ring,Transmission And Steering Case | 1 |
| 07***12 | Gasket,Mechanical Pump Piping | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Starting Motor (11kw) (Cold Terrain Spec.) (Inner Parts)(#69524-)
| 60***20 | Starting Motor Ass'Y,(11kw) | 1 |
| SD***X0 | Bearing,Ball | 1 |
| SD***X0 | Bracket,Rear | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Starting Motor (11kw) (Cold Terrain Spec.) (Inner Parts)(#86009-)
| 60***11 | Starting Motor Ass'Y,(11kw) | 1 |
| KD***40 | Spring,Spring | 4 |
| KD***57 | Bearing, Ball, Front | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Starting Motor (7.5kw) (Inner Parts)(#82046-)
| 60***11 | Starting Motor Ass'Y,(7.5kw) | 1 |
| KD***50 | Brush Assembly | 4 |
| KD***40 | Washer | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Starting Motor Mounting (11kw) (Cold Terrain (A) Spec.)(#86009-)
| 01***40 | Bolt (Kit) | 3 |
| 08***19 | Band,(Without Air Conditioner) | 1 |
| 62***10 | Gasket,(See Fig.A6210) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Starting Motor Mounting (11kw) (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***40 | Bolt,(For Slag Handling) (For Usa) | 3 |
| 08***19 | Band,(Without Air Conditioner) | 1 |
| 62***10 | Gasket,(See Fig.A6210) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Starting Motor Mounting (7.5kw) (Trimming Spec.)(#82046-)
| 01***40 | Bolt (Kit) | 3 |
| 08***19 | Band,(Without Air Conditioner) | 1 |
| 62***10 | Gasket,(See Fig.A6210) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Thermostat Housing
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 2 |
| 01***65 | Screw | 4 |
| 02***04 | Plug,(For Shipping) | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Water Drain Valve
| 61***12 | Valve,Water Drain | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Water Pump (Cold Terrain Spec.) (-40?C)(#69524-)
| 01***16 | Bolt - Seat And Tether Belt Mounting | 6 |
| 01***20 | Bolt,(For Mono Lever Steering) | 2 |
| 01***30 | Bolt,(With Body Positioner) | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Water Pump Gasket Kit(#69524-)
| 02***37 | O-Ring,(For Pc750?1800) (A5010) | 1 |
| 02***37 | O-Ring (K6) | 1 |
| 07***15 | O-Ring,Scavenge Pump | 1 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Water Pump(#75278-)
| 01***16 | Bolt - Seat And Tether Belt Mounting | 6 |
| 01***20 | Bolt,(For Mono Lever Steering) | 2 |
| 01***30 | Bolt,(With Body Positioner) | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Water Separator (Extreme Cold Terrain Spec.)(#78098-)
| 01***16 | Bolt, Battery To Frame Ground Wire Attaching | 1 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 4 |
| 01***30 | Bolt,(With Body Positioner) | 2 |
Komatsu : 6d125e-2a-40(S/N 61779-Up) : Engine : Water Temperature Sensor
| 07***15 | Plug,(Used When Without Heater) | 1 |
| 08***10 | Connector, Clip | 1 |
| 14***60 | Bracket | 1 |
6D125E-2A-40(S/N 61779-UP) serial number reference
The engine data plate is a metal tag fixed to the engine block, usually on the rocker/valve cover or the upper cylinder block near the fuel injection pump side, stamped with the full engine model code and serial number. This engine range uses a straight numeric serial sequence with no alphabetic prefix system; the trailing model-code suffix (here "-40") is the factory application/arrangement number tied to one specific machine fitment, and the number following S/N marks where that arrangement's production run begins.
| Prefix | Identifies | Notes |
|---|---|---|
| 6D125E-2A-40 | Naturally aspirated (non-turbo) application of the 6D125E-2 series diesel, factory-fitted to the Komatsu D65E-12 crawler dozer (equipment S/N 60942-Up). Inline 6-cylinder, direct injection, 125 x 150 mm bore and stroke, 11.04 L displacement, rated near 135 kW (180 HP) at 1950 rpm. The turbocharged S6D125E-2A sibling used on D65EX-12/D65P-12/D65PX-12 is a different engine model rated higher (about 153 kW / 205 HP) and is not part of this range. | This 6D125E-2A engine (S/N 61779-Up) is factory-fitted to the Komatsu D65E-12 crawler dozer (equipment S/N 60942-Up). The "-40" arrangement suffix is a distinct Komatsu factory arrangement number for the base 6D125E-2A model, separate from the "-45" and "-5" arrangements. The exact machine fitment tied to this specific "-40" arrangement is not separately documented beyond parts-catalog listings -- confirm the arrangement number against your engine plate with your dealer. |
Frequently asked questions
What engine powers the Komatsu 6D125E-2A-40(S/N 61779-UP)?
It is itself the engine: a naturally aspirated, water-cooled inline-six diesel from Komatsu's 125-series, 11.04 L (673.8 cu in) displacement with a 125 mm x 150 mm (4.92 in x 5.91 in) bore and stroke, rated near 142 kW (190 hp) at 1950 rpm. Komatsu built this application specifically for the D65E-12 crawler dozer, mechanically governed with no turbocharger or electronic controls.
What is the operating weight of the machine this engine powers?
Operating weight for the D65E-12 dozer runs roughly 14,870-19,125 kg (32,780-42,160 lb), depending on blade, ripper, and dash-configuration fitted. Varies by configuration/series, so confirm the exact build against the machine's own nameplate for a precise figure.
What replaced this engine and its host dozer?
This naturally aspirated 125-series application was superseded by the turbocharged, electronically controlled engines Komatsu introduced with the D65EX-15/D65PX-15 generation dozer in the early-to-mid 2000s, which later gave way to further D65-16/17/18 updates. Within its own 12-series generation, it also sat alongside the turbocharged S6D125E-2 used on the higher-output EX/PX chassis variants.
What 6D125E-2A-40(S/N 61779-UP) owners discuss
What's the general reputation of this naturally aspirated 6D125E-2A engine among owners and mechanics?
Widely described as simple and durable when upkeep is kept current: a mechanically governed, naturally aspirated diesel with no turbo or electronic engine controls to fail. Stories of engines running until they simply wear out, rather than breaking down, are common when oil changes and fuel filtration stay on schedule. The failure driver mechanics point to isn't the base design, it's neglected maintenance: contaminated fuel, stretched oil-change intervals, and mismatched aftermarket piston rings and liners causing wear inside months instead of years. Varies by duty cycle and how the previous owner ran it, but a properly maintained example of this engine family has a long-haul reputation.
Is coolant getting into the oil, or oil into the coolant, a known issue on this engine block?
Yes, it comes up repeatedly among mechanics working on this 125-series block. It has a reputation for weeping coolant past the head gasket over time, especially once the block has softened from age or a prior overheating event, which can erode the head surface. If the symptom is oil showing up in the coolant rather than the reverse, shop-manual guidance and mechanic consensus point first to the oil cooler core, since a cracked block or head is a far less common cause. Pressure-test the cooling system and pull a coolant and oil sample before assuming a full head gasket job is needed. Have your dealer verify before committing to teardown.
What undercarriage wear pattern should an owner expect on this dozer class?
Standard track-type dozer pattern: bushings, sprocket segments, and track shoes wear fastest, and undercarriage upkeep typically dominates the machine's lifetime repair cost. Operators and inspectors consistently flag heavy reverse travel and side-loading (angling or turning under load) as the two habits that accelerate wear fastest, since more scraping happens between bushing and sprocket tooth running in reverse than forward. Segment-style sprockets let a shop replace worn tooth sections without pulling the whole final drive, which owners note as a real savings over a one-piece sprocket design.
Are there known torque converter or TORQFLOW transmission issues on this dozer family?
The recurring mechanic complaint is torque converter overheating traced back to an internal leak in the forward clutch that lets oil bypass the transmission oil cooler, so converter temperature climbs without any obvious external leak to chase. It can take a long troubleshooting cycle to isolate because the symptom looks like a cooling-system fault rather than an internal clutch-seal problem. If a candidate machine runs hot on the torque converter gauge under load, budget for a possible forward-clutch reseal, not just a radiator or cooler flush. Have your dealer verify with a pressure and flow test before replacing parts.
What steering clutch, brake, and hydraulic wear points should be expected?
Steering clutch packs and brake bands wear over time like any wet-clutch steering system, and they're filtered on their own circuit separate from the main transmission, with a pressure filter that has its own air-purge point that's easy to miss during service. A frequent complaint is oil weeping from around the belly pan, usually traced to a steering clutch or brake seal, a hydraulic line, or a pump gasket rather than the engine itself. Low or contaminated hydraulic oil is treated as a direct driver of both steering clutch slippage and brake wear, not just implement performance, so reservoir condition matters for powertrain life too.
What electrical or sensor issues come up on this dozer's dash and controls?
Instrument panel and gauge dropouts are a recurring complaint, and mechanics usually trace them to blown fuses in the main fuse box, corroded or loose connectors behind the dash, and weak ground connections rather than a failed gauge cluster. Because this generation runs a largely mechanical control system compared to later electronically-controlled machines, a single bad connector or sensor can trigger several warning symptoms at once that look like unrelated failures. Cleaning and reseating connectors and verifying grounds before condemning a sensor or gauge is the consensus first troubleshooting step.
What should a buyer check before purchasing a used dozer built on this engine?
Pull maintenance and oil-analysis history first; a machine on a documented PM program is worth materially more than one without records. On the engine, sample both coolant and oil for cross-contamination given this block's known head-gasket and oil-cooler weep points. On the undercarriage, measure track shoe height and bushing and link wear against OEM minimums; an independent undercarriage inspection is standard practice on machines this size since it drives negotiated price. Run the machine and watch torque converter temperature under load, and cycle the steering clutches and brakes checking for slippage or delayed response. Have your dealer verify any borderline finding with a proper inspection before committing to purchase.
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
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