Komatsuengine(no series)
Komatsu 6D125E-2H(S/N 61779-UP)
Maintenance schedule, common problems & OEM parts breakdown
The Komatsu 6D125E-2H engine powers the D60A-6 series crawler dozers and PL-6 motor graders produced from approximately 2000 onward. This inline-six diesel unit delivers 135 kW (180 HP) for the D65E dozer configuration and is part of the broader 125 Series lineage that succeeded the 6D125-1. The engine supports a weight range of 19,000 to 25,000 lbs for the dozer class and 15,000 to 20,000 lbs for the grader class. Configurations include standard torque converter transmissions for dozers and hydrostatic drives for graders. The 6D125E-2H succeeded the 6D125-1F and was later replaced by the 6D125-1F in the D60A-8 series.
Across the 125 Series generations, the primary changes involved emissions compliance updates and turbocharger efficiency improvements. The 6D125E-2H remains critical in the used market due to its robust cast-iron block and widespread use in the D60 and PL-6 platforms. These machines are valued for their simplicity and ease of repair compared to newer Tier 4 models. The engine's longevity and the availability of aftermarket overhaul kits keep it relevant for fleet managers seeking cost-effective earthmoving solutions.
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-2H(S/N 61779-UP) specifications
Engine
| Model | 6D125E-2H |
| Type | 4-stroke cycle, water-cooled, direct injection, inline vertical type with turbocharger |
| Displacement | 11.0 liter (671.4 cu in) |
| Cylinders | 6 |
| Bore | 125 mm (4.92 in) |
| Stroke | 150 mm (5.91 in) |
| Power | 228-235 kW (306-315 hp) @ 1950 rpm (varies by configuration/series) |
Weights
| Engine Weight | the OEM part reference kg (2138-2425 lb) |
Dimensions
| Engine Dimensions | Length 1500-1800 mm (59.1-70.9 in), Width 900 mm (35.4 in), Height 1200-1500 mm (47.2-59.1 in) (varies by configuration/series) |
Performance
| Torque | 1,010 lbf·ft (1,370 N·m) |
| Fuel Consumption | 18.5 gal/hr (70 L/hr) at rated power |
Service capacities (summary)
| Fluid Recommendations | Diesel engine oil: Komatsu EO or equivalent; Hydraulic oil: Komatsu HO or equivalent; Coolant: Super-coolant AF-NAC |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
Komatsu 6D125E-2H(S/N 61779-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 6D125E-2H(S/N 61779-UP) beyond the schedule
Predictive Maintenance & Fluid Analysis
Utilize KOWA fluid analysis at every 500-hour interval to monitor wear metals and contamination levels. Check coolant SCA concentration at 500 hours to prevent cavitation in the 6D125E-2H cylinder liners. Monitor hydraulic oil particle count to protect the PL-6 hydrostatic pump. Track engine oil viscosity changes to detect fuel dilution from the direct injection system. Analyze final drive oil for gear wear indicators. Use KOMTRAX telematics to track load frequency and adjust fluid sampling intervals based on actual duty cycles rather than fixed hours.
Corrective & Common Repairs
Address injector nozzle coking by inspecting fuel lines and replacing clogged nozzles if black smoke persists. Replace turbocharger seals if blue smoke indicates oil leakage into the intake. Check the fuel injection pump timing if the engine struggles to reach rated RPM. Inspect the water separator daily to prevent water contamination of the high-pressure fuel system. Replace worn piston rings if compression drops below specification. Repair hydraulic hose leaks promptly to maintain pressure for the D60A-6 dozer blade control valves.
Overhaul & Rebuild Points
Plan an out-of-frame overhaul when cylinder liner wear exceeds limits or piston crown damage is evident. Replace main and connecting rod bearings if oil pressure drops significantly. Inspect the crankshaft for journal wear during any major service. Replace the cylinder head gasket if coolant leaks into the oil or combustion chamber. Rebuild the fuel injection pump if delivery rates are inconsistent. Replace the turbocharger if shaft play exceeds tolerance or compressor blades are damaged. Use a complete overhaul kit to ensure proper clearances for the 6D125E-2H.
Seasonal & Environment Servicing
In cold climates, use Komatsu Super Coolant AF-NAC to prevent freezing and ensure proper glycol concentration. Install block heaters if ambient temperatures drop below -10°C. In dusty environments, clean the air filter outer element more frequently and check the restriction indicator often. In high-humidity areas, drain the fuel separator daily to prevent water accumulation. Inspect the radiator and oil cooler fins for debris buildup to maintain cooling efficiency. Use Komatsu TO30 powertrain oil in warmer temperatures and TO10 in colder conditions for optimal viscosity.
6D125E-2H(S/N 61779-UP) common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| 07281-00197 | Clamp,(With Pre-Fuel Filter) | Fuel system service | Check fitment → |
| ND092220-0040 | Filter,Fuel | Fuel system service | Check fitment → |
| 09019-08035 | Wrench,Filter (For Add. Fuel Filter) | Fuel system service | Check fitment → |
| 09637-30163 | Plate? Instruction,Air Cleaner (Single Element) | Air intake service | Check fitment → |
| 09637-30263 | Plate? Instruction,Air Cleaner Element Mainte | Air intake service | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
6D125E-2H(S/N 61779-UP) fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| CA115 | Engine crankshaft speed sensor failure | Broken sensor, wiring issue, or connector corrosion | Replace the speed sensor and verify the voltage at the pin connector |
| CA111 | Internal engine controller fault | ECM hardware or software failure | Replace or reprogram the ECM |
| 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 |
| CA122 | Intake air pressure high voltage | Sensor malfunction or wiring issue | Verify the intake pressure sensor and wiring |
| CA123 | Intake air pressure low voltage | Sensor short or airflow restriction | Check for a sensor short or an airflow restriction |
| CA441 | Battery voltage too low | Weak battery or charging system issue | Replace the alternator or battery; check the voltage regulator |
| CA442 | Battery voltage too high | Faulty voltage regulator or alternator | Replace the alternator or battery; check the voltage regulator |
| CA234 | Engine overspeed | Throttle calibration error, engine load cycle issue, or operator misuse | Verify throttle calibration, engine load cycle, or operator misuse |
| CA153 | Intake air temperature sensor feedback voltage too high | Sensor malfunction | Replace or test the IAT sensor |
| CA154 | Intake air temperature sensor feedback voltage too low | Sensor malfunction | Replace or test the IAT sensor |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
6D125E-2H(S/N 61779-UP) attachments & work tools
Dozer Blades
Factory configurations for the D65E-12 series (S/N 60001-Up) include the Semi-U Tilt dozer blade and the Straight Tilt dozer blade. The Semi-U Tilt blade is specified for the D65E model, while the Straight Tilt blade is specified for the D65P model. Both blade types are designed to combine high power output with outstanding productivity for this machine class.
Undercarriage & Track Components
Track gauge specifications vary by model variant within the D65E-12 series. The D65E-12 and D65EX-12 models utilize a 1,880 mm track gauge, while the D65P-12 and D65PX-12 models utilize a 2,050 mm track gauge. Standard track shoe width is 510 mm for the D65E-12 and D65EX-12, and 950 mm for the D65P-12 and D65PX-12.
Cab & ROPS Configurations
Overall machine height varies based on the operator protection structure installed. When a ROPS cab is installed, the height is 3,160 mm for the D65E-12 and D65EX-12, and 3,195 mm for the D65P-12 and D65PX-12. When a ROPS canopy is installed, the height is 2,995 mm for the D65E-12 and D65EX-12, and 3,030 mm for the D65P-12 and D65PX-12.
Engine & Powertrain
The D65E-12 is powered by the 6D125E-2 diesel engine, while the D65P-12 is powered by the S6D125E-2 diesel engine. Both are 4-stroke, water-cooled, direct injection engines with turbochargers. The 6D125E-2 provides 135 kW (180 HP), and the S6D125E-2 provides 142 kW (190 HP). Power is transmitted to the final drives via a Komatsu Torqflow transmission with a high-efficiency torque converter.
Hydraulic & Control Systems
The D65E-12 features left-hand joystick controls for all tractor motion and right-hand joystick controls for all blade movements. The machine utilizes a low-noise design with powertrain components and rubber pads to soften vibration and shut out noise. Blade tilt lines are completely protected in the standard configuration.
All 6D125E-2H(S/N 61779-UP) assemblies by section
Every catalogued assembly group for the Komatsu 6D125E-2H(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-2h(S/N 61779-Up) : Engine : Air Cleaner Cap(#64065-81733)
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Air Cleaner Cap(#80455-)
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Air Cleaner(#64065-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 2 |
| 01***40 | Bolt (Op) | 1 |
| 01***08 | Nut,(For Straight Tilt Dozer) (D65p) | 6 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Air Intake Manifold(#64065-)
| 01***30 | Bolt,(With Body Positioner) | 15 |
| 01***55 | Bolt,(See Service News) | 5 |
| 01***10 | Bolt,(With Joy Stick Steering) | 8 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Air Vent(#64065-75182)
| 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-2h(S/N 61779-Up) : Engine : Air Vent(#75183-)
| 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-2h(S/N 61779-Up) : Engine : Alternater (35a) (With Hardening Pulley) (Sandy And Dusty Spec.) (Inner Parts)(#64065-)
| 60***50 | Alternator A. (35a) | 1 |
| 60***51 | Alternator A. (35a) | 1 |
| KD***50 | Bracket,Rear | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Alternater (35a) (With Hardening Pulley) (With Safety Cover) (Sandy And Dusty Spec.) (Inner Parts)(#64065-)
| 60***50 | Alternator A. (35a) | 1 |
| 60***51 | Alternator A. (35a) | 1 |
| KD***50 | Bracket,Rear | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Alternater (35a) (With Non Hardening Pulley) (Cold Terrain (A) Spec.) (Inner Parts)(#64065-)
| 60***50 | Alternator A. (35a) | 1 |
| 60***51 | Alternator A. (35a) | 1 |
| KD***50 | Bracket,Rear | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Alternater (35a) (With Non Hardening Pulley) (With Safety Cover) (Inner Parts)(#64065-)
| 60***50 | Alternator A. (35a) | 1 |
| 60***51 | Alternator A. (35a) | 1 |
| KD***50 | Bracket,Rear | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Alternater Mounting (35a) (With Hardening Pulley) (Sandy And Dusty Spec.)(#64065-)
| 01***60 | Bolt,(F4320-52a0 -5- ) | 4 |
| 01***75 | Bolt - Tube Mounting | 1 |
| 01***55 | Screw | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Alternater Mounting (35a) (With Hardening Pulley) (With Safty Cover) (Sandy And Dusty Spec.)(#64065-)
| 01***60 | Bolt,(F4320-52a0 -5- ) | 4 |
| 01***75 | Bolt - Tube Mounting | 1 |
| 01***55 | Screw | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Alternater Mounting (35a) (With Non Hardening Pulley) (Cold Terrain (A) Spec.)(#64065-)
| 01***60 | Bolt,(F4320-52a0 -5- ) | 4 |
| 01***75 | Bolt - Tube Mounting | 1 |
| 01***55 | Screw | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Alternater Mounting (35a) (With Non Hardening Pulley) (With Safety Cover) (Cold Terrain (A) Spec.)(#64065-)
| 01***60 | Bolt,(F4320-52a0 -5- ) | 4 |
| 01***75 | Bolt - Tube Mounting | 1 |
| 01***55 | Screw | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Blind Plug (Without Water Temperature Sensor)(#64065-)
| 07***15 | Plug,(Used When Without Heater) | 1 |
| 07***15 | Plug,(For Without Air Compressor) | 1 |
| 28***70 | Plug,(For Shipping) | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Camfollower Cover(#64065-)
| 07***20 | Clamp, Spring Hose | 1 |
| 07***63 | Hose | 1 |
| 61***90 | O-Ring,Breather | 1 |
Komatsu : 6d125e-2h(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-2h(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-2h(S/N 61779-Up) : Engine : Caution Plate (English)(#80455-)
| 09***63 | Plate? Instruction,Air Cleaner (Single Element) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Caution Plate (French)(#80455-)
| 09***63 | Plate? Instruction,Air Cleaner Element Mainte | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Caution Plate (German)(#80455-)
| 09***63 | Plate? Instruction,Air Cleaner Element Mainte | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Cooling Fan (Noise Suppression Spec.)(#64065-)
| 01***30 | Bolt,(With Body Positioner) | 12 |
| 60***40 | Fan,Cooling | 1 |
| 61***90 | Spacer | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Cooling Fan (Reversible Fan)(#64065-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 6 |
| 01***40 | Bolt (Op) | 6 |
| 60***40 | Fan,Reversible | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Cooling Fan(#64065-)
| 01***30 | Bolt,(With Body Positioner) | 6 |
| 01***40 | Bolt (Op) | 6 |
| 60***40 | Fan,Cooling | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Corrosion Resistor(#64065-)
| 01***16 | Bolt, Battery To Frame Ground Wire Attaching | 1 |
| 01***30 | Bolt,(With Body Positioner) | 4 |
| 02***25 | Bolt,(Cold Weather Spec.) | 4 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Crank Pulley (Hardening Pulley)(#64065-)
| 01***15 | Bolt | 1 |
| 01***20 | Bolt | 5 |
| 04***28 | Pin, Dowel - Transmission Case, Pin-Dowel | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Crank Pulley (Non Hardening Pulley)(#64065-)
| 01***15 | Bolt | 1 |
| 01***20 | Bolt | 5 |
| 04***28 | Pin, Dowel - Transmission Case, Pin-Dowel | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Crankshaft(#61779-67073)
| 61***10 | Bearing, Main (Standard) | 7 |
| 61***50 | Bearing, Thrust Assembly (Standard) | 1 |
| 61***10 | Bearing, Main (1.00mm Undersize) | 7 |
Komatsu : 6d125e-2h(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-2h(S/N 61779-Up) : Engine : Cylinder Block (1/2)(#64065-76893)
| 01***12 | Bolt,(Without Air Compressor Type) | 2 |
| 01***45 | Washer,(For Travel Motor) (Not Show) | 14 |
| 04***14 | Pin, Dowel | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Cylinder Block (2/2)(#64065-76893)
| 01***20 | Bolt,(For Mono Lever Steering) | 4 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 5 |
| 07***30 | Ring, Seal - Between Sections | 1 |
Komatsu : 6d125e-2h(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-2h(S/N 61779-Up) : Engine : Cylinder Block Blind Cover And Plug(#76894-)
| 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-2h(S/N 61779-Up) : Engine : Cylinder Block Gasket Kit(#64065-)
| 07***21 | O-Ring,Water Piping | 1 |
| 07***30 | Ring, Seal - Between Sections | 1 |
| 07***15 | O-Ring,Relief Valve | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Cylinder Head Gasket Kit(#64065-)
| 07***65 | O-Ring,Cylinder Block | 6 |
| 07***12 | Gasket,Mechanical Pump Piping | 12 |
| 07***12 | Gasket,(Without Air Compressor Type) (K2) | 12 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Cylinder Head(#61779-67991)
| 01***20 | Bolt (M10-1.75x120) | 6 |
| 04***20 | Pin,Dowel (Welded) | 2 |
| 07***08 | Plug,(Without Lock-Up), Plug | 1 |
Komatsu : 6d125e-2h(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-2h(S/N 61779-Up) : Engine : Damper(#64065-)
| 01***50 | Bolt,For Weight Adjusting Bolt | 6 |
| 61***20 | Plate | 1 |
| 61***00 | Damper Ass'Y | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Engine Mounting(#64065-)
| 01***40 | Bolt,R.H. Outside And L.H. Inside, Bolt | 4 |
| 01***50 | Bolt,(Shim Thickness?Less Than 8mm) | 4 |
| 01***55 | Bolt,(Tree Pusher Dozer) | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Exhaust Manifold
| 01***80 | Screw | 18 |
| 07***08 | Plug,(Without Auto Priming System) | 1 |
| 61***20 | Spacer,(For Shipping) | 18 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Exhaust Manifold (With Safety Cover)(#64065-79012)
| 01***20 | Bolt | 4 |
| 01***25 | Bolt,Joint | 2 |
| 01***45 | Capscrew | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Exhaust Manifold (With Safety Cover)(#79013-)
| 01***20 | Bolt | 4 |
| 01***25 | Bolt,Joint | 2 |
| 01***45 | Capscrew | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Exhaust Pipe (502.9mm)(#80455-)
| 01***11 | Nut (M14-1.50 Thd), Nut; Was 01582-01411 | 2 |
| 61***20 | Clamp | 1 |
| 61***70 | Washer,(Spark Arrester Spec.) | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Exhaust Pipe (Black Exhaust Pipe? 1013mm)(#80455-)
| 01***11 | Nut (M14-1.50 Thd), Nut; Was 01582-01411 | 2 |
| 61***20 | Clamp | 1 |
| 61***90 | Tube, Exhaust Stack (Glass Wool) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Exhaust Pipe (Silver Exhaust Pipe? 1013mm) (With Rain Cap)(#80455-)
| 01***11 | Nut (M14-1.50 Thd), Nut; Was 01582-01411 | 2 |
| 61***20 | Clamp | 1 |
| 61***70 | Washer,(Spark Arrester Spec.) | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fan Drive (Noise Suppression Spec.)(#64065-)
| 01***30 | Bolt,(With Body Positioner) | 4 |
| 01***40 | Bolt (Op) | 2 |
| 01***95 | Capscrew | 4 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fan Drive(#64065-)
| 01***30 | Bolt,(With Body Positioner) | 4 |
| 01***40 | Bolt (Op) | 2 |
| 01***95 | Capscrew | 4 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fan Pulley (For 35a Alternator) (Ec? Dynamic Noise Suppression)(#72957-)
| 01***30 | Bolt,(With Body Positioner) | 6 |
| 04***70 | V-Belt Set,(Noise Suppression Spec.) | 1 |
| 61***30 | Pulley,Hardening | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fan Pulley (Hardening Pulley) (Sandy And Dusty Spec.) (For 35a Alternator)(#64065-)
| 04***67 | V-Belt Set,(Tropical Sandy? Dusty Spec.) | 1 |
| 61***61 | Pulley? Hardening | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fan Pulley (Non Hardening Pulley) (For 35a Alternator)(#64065-)
| 04***67 | V-Belt Set,(Tropical Sandy? Dusty Spec.) | 1 |
| 61***21 | Pulley?Non Hardening,Non Hardening | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fan Pulley (Non Hardening Pulley) (Noise Suppression Spec.) (For 35a Alternator)(#64065-)
| 01***30 | Bolt,(With Body Positioner) | 6 |
| 04***69 | V-Belt Set,Fan | 1 |
| 61***30 | Pulley?Non Hardening | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Flywheel Housing(#64065-)
| 01***65 | Bolt - Battery Box | 2 |
| 01***50 | Capscrew | 6 |
| 01***65 | Capscrew | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Flywheel(#64065-)
| 01***65 | Bolt | 6 |
| 01***45 | Washer,(For Travel Motor) (Not Show) | 6 |
| 61***41 | Gear, Ring | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Front Cover Mounting(#76796-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 1 |
| 01***65 | Bolt - Return Line And Suction Linehose Clamps | 8 |
| 01***75 | Bolt (M10-1.50x75) | 4 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Front Cover(#64065-76886)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 1 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 1 |
| 01***65 | Bolt - Return Line And Suction Linehose Clamps | 8 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Front Cover(#76796-)
| 09***50 | Liquid Gasket, Lg-7, 150g | 0 |
| 61***30 | Seal? Front (K2) | 1 |
| 61***80 | Cover,Front | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fuel Filter(#64065-)
| 01***30 | Bolt,(With Body Positioner) | 4 |
| 01***35 | Bolt,(F4320-52a0 -5 ) | 2 |
| 01***16 | Washer,Radio Controlled Slag Handling | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fuel Injection Pump (Coupling) (Inner Parts)(#64065-)
| ND***10 | Flange,Coupling | 1 |
| ND***50 | Bolt | 1 |
| ND***40 | Bolt | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fuel Injection Pump (Feed Pump) (Inner Parts)(#64065-)
| ND***40 | Washer? 1mm,Plate | 1 |
| ND***70 | Washer,Union | 4 |
| ND***10 | Spring, Check Valve | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fuel Injection Pump (Governor) (1/2) (Inner Parts)(#64065-)
| ND***40 | Plate,Thrust | 1 |
| ND***40 | Plug,Screw | 1 |
| ND***10 | Adapter | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fuel Injection Pump (Governor) (2/2) (Inner Parts)(#64065-)
| ND***20 | Washer? 1.0mm,Cover Plate | 2 |
| ND***90 | Seal,Oil | 1 |
| ND***40 | O-Ring | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fuel Injection Pump (Pump) (1/2) (Inner Parts)(#64065-)
| 61***20 | Injection Pump Ass'Y | 1 |
| 61***21 | Injection Pump Ass'Y | 1 |
| ND***20 | Body Ass'Y | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fuel Injection Pump (Pump) (2/2) (Inner Parts)(#64065-)
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fuel Injection Pump Drive
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 4 |
| 01***14 | Nut (Itl) | 1 |
| 01***60 | Washer,(Without Rops Guard? Canopy) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fuel Injection Pump Mounting(#64065-)
| 01***75 | Capscrew | 4 |
| 61***10 | Washer,Spring | 4 |
| (6***0) | Injection Pump Ass'Y,(See Fig.A4010-B3l1) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fuel Injection Pump Piping
| 01***30 | Screw | 4 |
| 01***55 | Bolt,(See Service News) | 4 |
| 01***70 | Bolt - Bracket And Oil Inlet Tubemounting | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Fuel Return(#64065-)
| 01***20 | Bolt,(For Mono Lever Steering) | 1 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 1 |
| 01***08 | Nut,(For Canvas Canopy?Head Guard) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Head Cover Related Parts(#76208-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 1 |
| 01***00 | Bolt,(For Front Brake Release) | 2 |
| 01***08 | Nut,(For Canvas Canopy?Head Guard) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Head Cover(#64065-76207)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 1 |
| 01***00 | Bolt,(For Front Brake Release) | 2 |
| 01***08 | Nut,(For Canvas Canopy?Head Guard) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Head Cover(#76208-)
| 01***16 | Washer,Radio Controlled Slag Handling | 24 |
| 61***11 | Cover,Head? No.2?3?4?5?6 | 5 |
| 61***41 | Head Cover Ass'Y,Head? No.1 | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Heater Signal(#64065-81509)
| 60***30 | Signal,Engine Pre Heater | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Heater Signal(#80455-)
| 60***30 | Signal,Engine Pre Heater | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Heater Switch(#64065-)
| 01***16 | Bolt - Box Mounting | 2 |
| 01***55 | Bolt,(See Service News) | 1 |
| 01***10 | Washer,(For 35a Alternator) | 2 |
Komatsu : 6d125e-2h(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-2h(S/N 61779-Up) : Engine : Injection Nozzle(#64065-81733)
| 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-2h(S/N 61779-Up) : Engine : Injection Nozzle(#81734-)
| 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-2h(S/N 61779-Up) : Engine : Muffler (Black Exhaust Pipe? 1013mm) (With Safety Cover)(#64065-81733)
| 01***12 | Bolt - Front Cover Mounting | 15 |
| 01***40 | Bolt (Op) | 4 |
| 01***25 | Bolt,Joint | 4 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Muffler (Black Exhaust Pipe? 1013mm)(#64065-81733)
| 01***40 | Bolt (Op) | 4 |
| 01***25 | Bolt,Joint | 4 |
| 01***30 | Bolt | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Muffler (Exhaust Pipe? 502.9mm) (With Safety Cover)(#64065-81733)
| 01***12 | Bolt - Front Cover Mounting | 15 |
| 01***40 | Bolt (Op) | 4 |
| 01***25 | Bolt,Joint | 4 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Muffler (Exhaust Pipe? 502.9mm)(#64065-81733)
| 01***40 | Bolt (Op) | 4 |
| 01***25 | Bolt,Joint | 4 |
| 01***30 | Bolt | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Muffler (For Ec Reguration)(#81002-)
| 01***12 | Bolt - Front Cover Mounting | 15 |
| 01***40 | Bolt (Op) | 4 |
| 01***25 | Bolt,Joint | 4 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Muffler (Silver Exhaust Pipe? 1013mm) (With Rain Cap)(#64065-81001)
| 01***40 | Bolt (Op) | 4 |
| 01***25 | Bolt,Joint | 4 |
| 01***30 | Bolt | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Muffler (Silver Exhaust Pipe? 1013mm) (With Safety Cover) (With Rain Cap)(#64065-81001)
| 01***12 | Bolt - Front Cover Mounting | 15 |
| 01***40 | Bolt (Op) | 4 |
| 01***25 | Bolt,Joint | 4 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Muffler(#81002-)
| 01***12 | Bolt - Front Cover Mounting | 15 |
| 01***40 | Bolt (Op) | 4 |
| 01***25 | Bolt,Joint | 4 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Name Plate And Caution (English)(#64065-81509)
| 09***61 | Plate? Instruction,Air Cleaner (Single Element) | 1 |
| 09***63 | Plate? Instruction,Air Cleaner (Single Element) | 1 |
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Name Plate And Caution (English)(#77941-80914)
| 04***50 | Screw | 4 |
| 09***63 | Plate? Instruction,Air Cleaner (Single Element) | 1 |
| 61***10 | Plate? Name,(Limited Supply) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Name Plate And Caution (For Regulation Of Epa)(#80915-)
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Name Plate And Caution (French)(#64065-81509)
| 09***61 | Plate? Instruction,Air Cleaner (French) | 1 |
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
| 61***20 | Plate? Name,(French) (Limited Supply) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Name Plate And Caution (French-English)(#77941-80914)
| 04***50 | Screw | 4 |
| 09***63 | Plate? Instruction,Air Cleaner Element Mainte | 1 |
| 61***10 | Plate? Name,(Limited Supply) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Name Plate And Caution (German)(#64065-81509)
| 09***61 | Plate? Instruction,(German-English) (Not Shown) | 1 |
| 09***63 | Plate? Instruction,Air Cleaner Element Mainte | 1 |
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Name Plate And Caution (German-English)(#77941-80914)
| 04***50 | Screw | 4 |
| 09***63 | Plate? Instruction,Air Cleaner Element Mainte | 1 |
| 61***10 | Plate? Name,(Limited Supply) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Name Plate And Caution Plate (For Eu Exhaust Gas Regulation)(#80915-)
| 04***50 | Screw | 4 |
| 61***10 | Plate? Name,(Limited Supply) | 1 |
| 61***11 | Plate,(Limited Supply) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Name Plate And Caution Plate (For Regulation Of Epa)(#65969-66827)
| 04***50 | Screw | 4 |
| 09***63 | Plate? Instruction,Air Cleaner (Single Element) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Name Plate And Caution Plate (For Regulation Of Epa)(#66828-80914)
| 04***50 | Screw | 4 |
| 09***63 | Plate? Instruction,Air Cleaner (Single Element) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Name Plate And Caution(#80915-)
| 61***20 | Plate? Name,Engine (Limited Supply) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Nozzle Holder (Inner Parts)(#64065-81733)
| 07***12 | Gasket,Mechanical Pump Piping | 2 |
| 61***10 | Holder Ass'Y | 1 |
| ND***90 | Connector,Inlet | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Nozzle Holder (Inner Parts)(#81734-)
| 07***12 | Gasket,Mechanical Pump Piping | 2 |
| 61***10 | Holder Ass'Y | 1 |
| ND***90 | Connector,Inlet | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Oil Adapter(#64065-)
| 01***16 | Bolt, Battery To Frame Ground Wire Attaching | 1 |
| 01***35 | Bolt,(F4320-52a0 -5 ) | 2 |
| 01***50 | Bolt,(Spark Arrester Spec.) | 2 |
Komatsu : 6d125e-2h(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-2h(S/N 61779-Up) : Engine : Oil Cooler(#61779-76795)
| 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-2h(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-2h(S/N 61779-Up) : Engine : Oil Filter(#64065-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 2 |
| 01***30 | Bolt,(With Body Positioner) | 4 |
| 01***35 | Bolt,(F4320-52a0 -5 ) | 2 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Oil Level Gauge(#64065-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 1 |
| 01***35 | Bolt,(F4320-52a0 -5 ) | 1 |
| 01***08 | Nut,(For Canvas Canopy?Head Guard) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Oil Pan And Suction Tube(#64065-)
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 29 |
| 01***30 | Bolt,(For Quick Shift) (Mitsubishi) | 7 |
| 01***20 | Bolt,(For Mono Lever Steering) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Oil Pump
| 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-2h(S/N 61779-Up) : Engine : Piston
| 02***13 | Pin, Dowel | 2 |
| 04***18 | Ring, Snap | 12 |
| 61***10 | Pin,Piston | 6 |
Komatsu : 6d125e-2h(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-2h(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-2h(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-2h(S/N 61779-Up) : Engine : Spare Parts (Ec? Dynamic Noise Suppression)(#72961-81001)
| 04***70 | V-Belt Set,(Noise Suppression Spec.) | 1 |
| 07***34 | O-Ring,Transmission And Steering Case | 1 |
| 07***12 | Gasket,Mechanical Pump Piping | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Spare Parts (For 35a Alternetor)(#64065-80914)
| 04***67 | V-Belt Set,(Tropical Sandy? Dusty Spec.) | 1 |
| 07***34 | O-Ring,Transmission And Steering Case | 1 |
| 07***12 | Gasket,Mechanical Pump Piping | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Spare Parts (Noise Suppression Spec.)(#64065-80914)
| 04***69 | V-Belt Set,Fan | 1 |
| 07***34 | O-Ring,Transmission And Steering Case | 1 |
| 07***12 | Gasket,Mechanical Pump Piping | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Starting Motor (11kw) (Inner Parts)(#61779-86012)
| 60***10 | Starting Motor Ass'Y,(11kw) | 1 |
| SD***X9 | Switch Ass'Y,Engage | 1 |
| SD***X0 | Bearing,Ball | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Starting Motor (11kw) (Inner Parts)(#86013-)
| 60***11 | Starting Motor Ass'Y,(11kw) | 1 |
| KD***40 | Spring,Spring | 4 |
| KD***57 | Bearing, Ball, Front | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Starting Motor (7.5kw) (Inner Parts)
| 60***11 | Starting Motor Ass'Y,(7.5kw) | 1 |
| KD***60 | Shift Lever Assembly | 1 |
| KD***40 | Spring,Spring | 4 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Starting Motor Mounting (11kw)(#61779-86012)
| 01***40 | Bolt,(With Center Guard) | 3 |
| 01***40 | Bolt (Kit) | 3 |
| 08***19 | Band,(Without Air Conditioner) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Starting Motor Mounting (11kw)(#86013-)
| 01***40 | Bolt (Kit) | 3 |
| 08***19 | Band,(Without Air Conditioner) | 1 |
| 08***10 | Connector, Clip | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Starting Motor Mounting (7.5kw)
| 01***40 | Bolt,(With Center Guard) | 3 |
| 01***40 | Bolt (Kit) | 3 |
| 08***19 | Band,(Without Air Conditioner) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Tamper Proof Kit (For Regulation Of Epa)(#64065-)
| 61***10 | Tamper Proof Kit | 1 |
Komatsu : 6d125e-2h(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-2h(S/N 61779-Up) : Engine : Water Drain Valve
| 61***12 | Valve,Water Drain | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Water Pump Gasket Kit(#64065-)
| 02***37 | O-Ring,(For Pc750?1800) (A5010) | 1 |
| 07***15 | O-Ring,Scavenge Pump | 1 |
| 07***15 | O-Ring,(F4320-57a0 -11 ) | 1 |
Komatsu : 6d125e-2h(S/N 61779-Up) : Engine : Water Pump(#64065-75182)
| 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-2h(S/N 61779-Up) : Engine : Water Pump(#75183-)
| 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-2h(S/N 61779-Up) : Engine : Water Separator(#64065-)
| 01***25 | Bolt,(Rear Attachment Less) | 2 |
| 01***25 | Bolt,(For Canvas Canopy?Head Guard) | 2 |
| 01***16 | Washer,(For 35a Alternator) | 2 |
6D125E-2H(S/N 61779-UP) serial number reference
The engine PIN plate is located on the engine block, typically on the left side near the injection pump. Read the prefix as the alphanumeric engine model code (e.g., 6D125E-2H) followed by the sequential serial number stamped on the plate or block.
| Prefix | Identifies | Notes |
|---|---|---|
| 6D125E-2H | Engine Model | Identifies the 6D125E-2H engine family. Serial range 61779-UP applies to this specific engine variant. Verify with dealer for exact machine fitment as engine serials do not always match chassis serials. |
Frequently asked questions
What engine does the Komatsu D60A-6 use?
The Komatsu D60A-6 uses the 6D125E-2H engine for serial numbers 61779 and up.
What is the operating weight of the Komatsu D60A-6?
The operating weight varies by configuration, typically ranging from 19,000 to 25,000 lbs depending on the blade and counterweight setup.
What replaced the 6D125E-2H engine?
The 6D125-1F engine replaced the 6D125E-2H in the subsequent D60A-8 series production.
What 6D125E-2H(S/N 61779-UP) owners discuss
What are the known powertrain and hydraulic behaviors for the Komatsu 6D125E-2H engine series?
The 6D125E-2H series is characterized by high fuel efficiency and smooth operation. Community consensus indicates that Komatsu hydraulic systems are generally reliable but sensitive to oil viscosity and filter condition. A common diagnostic pattern is that if all hydraulic functions (boom, arm, bucket, swing, travel) become slow simultaneously, the issue is likely shared (hydraulic oil level, filters, or engine RPM) rather than a single pump failure. If only one function is slow, the focus shifts to that specific circuit's valve, cylinder, or hose. The engine is noted for being robust, but hydraulic weakness that appears only when the machine is hot often points to internal leakage in the pump or main control valve as oil viscosity decreases with temperature.
What undercarriage or wear patterns are typical for machines powered by this engine type?
Machines utilizing the 6D125E-2H engine, such as the D65E-12 dozer, feature heavy-duty undercarriage components designed for high-traction applications. Typical wear patterns include degradation of track pads, bushings, and bearings due to the high torque output and heavy operating weights. Community reports highlight that undercarriage components like rollers and idlers are subject to significant wear in dusty environments. While the engine itself is durable, the associated powertrain components (final drives, torque converters) transmit high stress to the undercarriage, leading to accelerated wear if track tension is not maintained correctly or if debris packs into the track frames.
What are the specific engine quirks or design features of the 6D125E-2H series compared to older designs?
The 6D125E-2H series utilizes hardened cylinder liners matched with high-alloy piston rings, a design improvement over older soft-liner configurations. It employs a high-pressure Bosch-style fuel injection system with injector pressures reaching approximately 3,200 PSI, contrasting with older low-pressure systems. The engine is a 4-stroke, water-cooled, direct-injection inline-six with a turbocharger. A notable operational quirk is the sensitivity of the fuel system to air ingress; if the machine stops starting immediately after filter replacement, air leaks in the fuel supply lines are a primary suspect before assuming high-pressure component failure. The engine is also noted for its compact dimensions relative to its power output.
What are common electrical or sensor issues reported for this engine platform?
Komatsu equipment with this engine platform relies heavily on electronic control systems. Common reported issues include intermittent starting, dashboard display failures, and random machine shutdowns, often triggered by a single faulty sensor or unstable power supply. Multiple fault codes appearing simultaneously typically point to battery state of charge, poor engine/chassis grounds, or corroded connectors rather than individual sensor failures. Operators are advised to perform voltage-drop tests on the starter circuit under load, as batteries may show acceptable voltage at rest but collapse under the high current demand of starting.
What should be checked when buying a used machine with a 6D125E-2H engine (S/N 61779-UP)?
When inspecting a used machine with this engine serial range, verify the exact model suffix and serial prefix against the machine's data plate, as specifications vary by configuration. Check the condition of the hardened liners and piston rings, as some owners report ring and liner wear within 6-8 months if non-OEM parts are used. Inspect the cooling package (radiator, hydraulic oil cooler, charge-air cooler) for packed debris between heat exchangers, which causes overheating during heavy work. Test hydraulic performance both cold and hot to identify internal leakage that worsens with temperature. Verify the integrity of the fuel system for air leaks, especially if filters have been recently changed. Check for signs of excessive undercarriage wear and track tensioner seal leaks, which are common maintenance items.
What are the recommended fluid specifications for this engine and its associated systems?
Komatsu specifies the use of Komatsu Genuine Lubricants and Coolants which exceed industry standards. Recommended fluids include Komatsu EO diesel engine oil, Komatsu TO hydraulic oil, Komatsu AXO axle oil, and Komatsu AF-NAC super coolant. For powertrain applications, Komatsu TO10 or TO30 powertrain oil is specified depending on the operating conditions. Using fluids that meet these specific Komatsu Engineering Standards is critical for maintaining component life and warranty compliance.
What is a safety-critical fix related to the cooling system that requires dealer verification?
If the cooling system becomes highly pressurized shortly after a cold start or if coolant is repeatedly expelled, this may indicate a deeper engine issue such as a blown head gasket or cracked component. This condition poses a risk of severe engine damage or injury from hot coolant ejection. Have your dealer verify the cooling system integrity and engine block condition immediately.
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
Need a specific 6D125E-2H(S/N 61779-UP) part?
Search live OEM part data, check fitment, and cross-reference alternatives with Heavy Parts AI.