Komatsuengine(no series)

Komatsu 6D125-1EE(S/N 21811-UP)

Maintenance schedule, common problems & OEM parts breakdown

Search live 6D125-1EE(S/N 21811-UP) parts

The Komatsu 6D125-1EE (engine S/N 21811-and-up) is a running-change variant within the 6D125-1 family: an 11.0-liter, 125 x 150 mm bore-and-stroke, in-line six-cylinder diesel from Komatsu's mechanically-governed engine generation of the 1980s-1990s. Parts-fitment records tie this specific engine serial break most consistently to the Komatsu D58P-1 and D58P-1B low-ground-pressure (swamp-shoe) crawler dozers, a roughly 12.6-15.7 t class machine built from the late 1980s into the mid-1990s and offered with straight-blade and power-angle-tilt configurations on standard and wide-swamp-shoe undercarriage. The wider 6D125-1 engine family, under different suffix letters and different engine-serial breaks, also powered other Komatsu dozers and motor graders of the same era, so this pairing should be read as the best-documented match for this exact serial range rather than a certainty; confirm the host chassis from your own machine's PIN and data plate.

Komatsu issued the 6D125-1 family in numerous suffix-coded running changes, each tied to a specific host-chassis serial break rather than to one universal power rating; that is why aggregated spec listings for '6D125-1' show a wide horsepower spread across different letter codes, and why a single confirmed rating for this exact EE suffix is not published outside dealer records. Every variant in the family shares the same core architecture: a Bosch-type inline injection pump, a mechanical centrifugal all-speed governor, and a water-cooled block with no factory electronic engine controls. In the used and parts market today, this generation is valued mainly as rebuildable long blocks, injection pump cores, and cylinder-head kits supporting older D58/D60-class dozers and same-era Komatsu motor graders still working construction, quarry, and forestry sites. Komatsu no longer supports this block through current dealer parts programs in most regions, so aftermarket and rebuilt-component suppliers are now the main source for keeping these units running.

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 6D125-1EE(S/N 21811-UP) specifications

Engine

Engine familyKomatsu 6D125-1 diesel block, EE running-change variant (engine S/N 21811-and-up)
ConfigurationIn-line 6-cylinder, water-cooled, naturally aspirated, mechanically governed diesel (pre-electronic fuel injection era)
Displacement / bore11.0 L (673.8 cu in / 11,042 cc), 125 mm bore
Gross powerNot independently confirmed for this exact engine suffix and serial range (21811-UP). The wider 6D125-1 family spans roughly 116-165 kW (155-180 hp) across different suffix codes and host machines of the same era; check the engine data plate or your dealer for the exact factory rating on this unit
Net powerNot published for this configuration
Emissions tierPre-emissions-regulation era (1980s mechanical governor; no EPA/Tier certification applies)

Weights

Operating weight (confirmed host: Komatsu D58P-1 / D58P-1B crawler dozer)Roughly 12.6-15.7 t (27,800-34,600 lb); published figures vary by source and by blade/undercarriage configuration
Shipping weightNot published for this configuration
Ground pressureNot published for this configuration — verify with your dealer

Dimensions

Transport dimensionsNot independently published for this exact engine serial range on its confirmed host chassis — refer to the factory shop manual for this serial range or your dealer

Performance

Travel speedNot documented for this exact engine serial range and host configuration — check the factory shop manual for this range or verify with your dealer
Gradeability / drawbar pullNot published for this configuration

Service capacities (summary)

Fuel tank, hydraulic system, engine oil, cooling systemNot published for this exact engine serial range and host configuration — refer to the factory shop manual for this range or your dealer for refill capacities

Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.

6D125-1EE(S/N 21811-UP) fluids & capacities

SystemCapacityRecommended fluid
Engine crankcase (with oil filter)Not independently published for this exact engine code and serial range. Komatsu dozers built on the same-era mechanical 6D125-1 block show a wide spread across chassis configurations, so no single figure applies without the machine's own plate data — check the dipstick or dealer record for this unit.Komatsu Genuine diesel engine oil (EO series), formulated to Komatsu's own engine-oil spec. Grade by ambient temperature: SAE 10W-30 for cold and variable climates, SAE 15W-40 for moderate-to-hot climates, SAE 30 monograde for sustained hot-climate duty.
Cooling system55-63 L (14.5-16.6 US gal); varies by configuration/series. No dedicated figure is published for this exact engine code — the range reflects contemporaneous same-block Komatsu dozer applications and should be confirmed against the specific host chassis.Komatsu Super Coolant (AF-NAC), a pre-mixed, nitrite-free ethylene-glycol long-life coolant with built-in corrosion inhibitors. Supplied pre-diluted for all-season use; do not weaken the mix ratio in cold climates.
Grease (spec only)No fixed refill quantity — apply at each grease fitting until fresh grease purges from the joint.Komatsu Genuine Grease G2-LI, a lithium EP2 multipurpose grease rated for roughly -20 C to +120 C service, used as the standard one-grease-for-most-points recommendation across Komatsu machines.

Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.

Komatsu 6D125-1EE(S/N 21811-UP) maintenance schedule

Service intervalTasks
Every 10 h
  • Check engine oil level before starting; top up to the full mark if low.
  • Check coolant level in the radiator or reserve tank when cold; top up with the correct antifreeze/water mix.
  • Drain water and sediment from the fuel water-separator/pre-filter bowl.
  • Walk around the engine and check for fuel, oil, and coolant leaks at the block, oil pan, and fuel lines.
  • Check the air cleaner restriction indicator; service the element if it shows red.
  • Weekly: grease accessible engine-mount and linkage points and check fan belt tension and condition.
Every 250 h
  • Change engine oil and replace the full-flow oil filter cartridge.
  • Replace the primary and secondary fuel filter cartridges.
  • Check and adjust fan belt tension.
  • Clean or replace the air cleaner outer element and check the dust discharge valve.
  • Check battery electrolyte level and clean/tighten terminal connections.
  • Clean radiator fins and cooling package of packed debris.
Every 500 h
  • Replace fuel filter cartridges again if operating in dusty or poor-fuel-quality conditions.
  • Inspect the exhaust manifold and muffler mounting for cracks or leaks.
  • Check governor and injection pump external linkage for free movement and wear.
  • Clean the crankcase breather/blow-by tube.
  • Check engine mounting bolts for looseness.
  • Check coolant corrosion-inhibitor concentration and top up as needed.
Every 1,000 h
  • Replace the fuel main filter cartridge.
  • Check injection nozzle spray pattern and opening pressure; recondition any nozzle that fails.
  • Replace the air cleaner outer element as scheduled service regardless of indicator reading.
  • Inspect radiator hoses for softening, swelling, or cracking and replace as needed.
  • Check alternator and starter mounting and wiring connections.
  • Check the crankshaft pulley and vibration damper for looseness or cracking.
Every 2,000 h
  • Check and adjust engine valve clearance.
  • Check fuel injection pump timing and reset to the factory mark if it has drifted.
  • Drain, flush, and refill the cooling system with fresh coolant and corrosion inhibitor.
  • Retorque cylinder head bolts to factory specification.
  • Inspect the vibration damper for oil leakage or rubber deterioration.
  • Bench-test injection pump output and calibration if power loss or rough running is reported.
Every 4,000 h
  • Send the injection pump out for bench overhaul or exchange at an authorized diesel shop.
  • Pull and bench-test injection nozzles as a matched set.
  • Run a compression or leak-down check on all cylinders to gauge liner and ring wear before scheduling a top-end rebuild.
  • Inspect the water pump for shaft play or seal weeping and rebuild or replace as needed.
Every 8,000 h
  • Plan a full in-frame or out-of-frame engine overhaul covering pistons, liners, rings, and main/rod bearings as a set.
  • Recondition the cylinder head: guides, seats, and valves as a set.
  • Rebuild or exchange the injection pump and governor assembly as a unit.
  • Inspect crankshaft journals for wear and regrind or replace if out of factory tolerance.

Servicing the 6D125-1EE(S/N 21811-UP) beyond the schedule

Predictive Maintenance & Fluid Analysis

Run scheduled oil sampling on this mechanically-governed 6D125-1EE block rather than relying on hours alone: track iron and copper trend lines from cylinder liners, wrist pins, and the gear-driven oil pump, since wear here shows up in oil chemistry before smoke or power loss appears. Watch coolant corrosion-inhibitor level between changes; low additive accelerates wet-liner cavitation on this block. Log fuel filter differential-pressure trend at every service to catch a failing lift pump or clogged primary filter before it starves the injection pump.

Corrective & Common Repairs

Typical corrective work on this mechanical fuel-system engine involves sticking or worn governor linkage causing hunting idle, worn injection pump plunger-and-barrel sets cutting power, and cracked high-pressure lines from vibration on the low-ground-pressure dozer chassis this variant most often served. Water pump seal weeping and glazed fan belts are common wear items on a block this age. With no factory electronic diagnostics on this pre-ECM engine, diagnosis relies on compression checks, injection timing marks, and manual governor adjustment rather than fault codes.

Overhaul & Rebuild Points

Top-end (in-frame) rebuild candidates on this block are cylinder liner and ring wear, valve seat recession, and injection nozzle spray-pattern degradation, best judged by compression test and nozzle bench test rather than a fixed hour count. A full out-of-frame overhaul at major hours should bundle crankshaft main and rod bearing replacement, injection pump bench calibration or exchange, and cylinder head reconditioning into one job. Because this is a mechanical, non-electronic engine, rebuild success depends on correctly resetting injection timing and governor settings on reassembly, not module reflashing.

Seasonal & Environment Servicing

Cold-climate starts on this mechanical, non-electronic block depend on a working cold-start aid, correct-viscosity engine oil, and sound battery condition, since there is no electronic cold-start compensation to fall back on. In hot, dusty, or wet low-ground-pressure worksite conditions, air cleaner restriction and radiator fin packing build up faster, so shorten air-filter and coolant-fin cleaning intervals from the standard chart. Drain the fuel water separator more often in humid or wet-season storage conditions typical of the swamp-dozer duty this engine variant most often sees.

6D125-1EE(S/N 21811-UP) common service parts

Part numberPart
07281-00197Clamp,(With Pre-Fuel Filter)Check fitment →
600-311-8291Cartridge,Fuel FilterCheck fitment →
6114-71-6200Fuel Filter Ass'YCheck fitment →
6114-71-6210Head, Fuel FilterCheck fitment →
ND092220-0040Filter,FuelCheck fitment →

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6D125-1EE(S/N 21811-UP) attachments & work tools

Blade Cutting Edges & Wear Parts

Bolt-on, through-hardened cutting edges and replaceable end bits protect the leading edge and corners of the machine's blade. These are wear items rather than optional work tools and are common across Komatsu machines built on the 6D125-1 engine block.

Rear Ripper / Scarifier

A rear-mounted ripper or scarifier with adjustable shank spacing is a common factory or dealer-fit option on machines of this class and era, used for breaking up hard or frozen ground ahead of dozing work. It typically draws off the machine's own rear hydraulic lift circuit rather than needing a separate pump kit.

Operator Guarding

Machines in this class and era were offered from the factory with either an open ROPS canopy or a fully enclosed ROPS/FOPS cab, depending on region and dealer package.

Host Chassis & Attachment Fitment

This engine was fitted to more than one Komatsu chassis type during its production run. Confirm your exact host machine from its own data plate before ordering attachments or work tools, since fitment and mounting hardware differ by chassis.

All 6D125-1EE(S/N 21811-UP) assemblies by section

Every catalogued assembly group for the Komatsu 6D125-1EE(S/N 21811-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Cooling System
Komatsu : 6d125-1ee(S/N 21811-Up) : Cooling System : Cooling Fan And Mounting
01***25Bolt,(For Canvas Canopy?Head Guard)6
01***30Bolt,(For Quick Shift) (Mitsubishi)10
01***40Bolt, Mount Master Brake Cylinder8
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cooling System : Corrosion Resistor And Piping
01***20Bolt,(For Quick Shift) (Mitsubishi)1
01***30Bolt,(For Quick Shift) (Mitsubishi)4
01***08Nut,(For Canvas Canopy?Head Guard)1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cooling System : Water Pump And Mounting
01***30Bolt,(For France Noise Suppression)2
01***16Bolt (With Air Heater & Conditioner)6
01***30Bolt,(For Quick Shift) (Mitsubishi)6
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Cylinder Block
Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Block : Camshaft
01***22Bolt2
04***25Key, Plain Woodruff1
04***12Ring,Snap (For Ripper)12
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Block : Crankshaft
01***50Bolt,(For Strengthened Cover)6
01***15Bolt1
01***20Bolt5
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Block : Cylinder Block
01***12Bolt,(Without Air Compressor Type)2
01***45Washer,(For Travel Motor) (Not Show)14
04***14Pin, Dowel2
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Block : Cylinder Block Cover
01***20Bolt,(For Quick Shift) (Mitsubishi)1
01***25Bolt,(For Canvas Canopy?Head Guard)1
01***08Nut,(For Canvas Canopy?Head Guard)1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Block : Flywheel And Flywheel Housing(#21811-32669)
01***40Bolt,(Dust And Dirt Protection)2
01***50Bolt, Radiator To Frame6
01***65Bolt - Battery Box2
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Block : Flywheel And Flywheel Housing(#32670-)
01***40Bolt,(Dust And Dirt Protection)2
01***50Bolt, Radiator To Frame6
01***65Bolt - Battery Box2
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Block : Front Cover And Front Support(#21811-34801)
01***25Bolt,(Without Auto Priming System)6
01***60Screw1
01***25Bolt,(For Canvas Canopy?Head Guard)1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Block : Front Cover And Front Support(#34802-)
01***25Bolt,(Without Auto Priming System)6
01***30Bolt,(For France Noise Suppression)6
01***60Screw1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Block : Oil Pan
01***25Bolt,(For Canvas Canopy?Head Guard)29
01***30Bolt,(For Quick Shift) (Mitsubishi)7
01***16Washer,Radio Controlled Slag Handling36
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Block : Piston And Connecting Rod
02***13Pin, Dowel2
04***18Ring, Snap12
61***32Piston Ring Ass'Y6
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Cylinder Head
Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Head : Air Cleaner And Mounting
01***25Bolt,(For Canvas Canopy?Head Guard)2
01***40Bolt, Mount Master Brake Cylinder1
01***08Nut,(For Straight Tilt Dozer) (D65p)6
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Head : Air Intake Manifold And Connection
01***16Bolt, Mount Washer Tank To Bracket, Bolt2
01***30Bolt,(For Quick Shift) (Mitsubishi)15
01***55Bolt, Mount Tube To Switch Pump5
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Head : Cylinder Head(#21811-26697)
04***20Pin,Dowel (Welded)2
61***30Sleeve,Holder1
61***20Cotter, Valve48
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Head : Cylinder Head(#26698-)
04***20Pin,Dowel (Welded)2
61***30Sleeve,Holder1
61***20Cotter, Valve48
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Head : Exhaust Manifold
01***80Bolt, Mount Strainer Flange18
07***08Plug,(Without Auto Priming System)1
61***20Spacer,(For Shipping)18
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Head : Muffler And Mounting
01***25Bolt,(Sandy? Dusty Terrain Spec.)4
01***40Bolt,(Dust And Dirt Protection)4
01***30Bolt, Mount Pump2
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Head : Rocker Arm And Housing
01***08Nut,R.H. Thread12
01***16Washer,Radio Controlled Slag Handling40
01***32Washer,(With Auto Emergency Steering)40
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Head : Rocker Arm Housing Cover
01***25Bolt,(For Canvas Canopy?Head Guard)1
01***00Bolt, Mount Back-Up Alarm2
01***08Nut,(For Canvas Canopy?Head Guard)1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Cylinder Head : Water Manifold And Thermostat
02***43O-Ring,Water Manifold6
07***12Washer, Gasket,(Without Thermo Sensor) (K1)1
07***08Plug,(Without Auto Priming System)1
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Electrical System
Komatsu : 6d125-1ee(S/N 21811-Up) : Electrical System : Alternator (13a)
60***50Alternator A. (13a),(With Non Hardening Pulley)1
KD***31Bushing,Insulator2
KD***72Slip Ring Ass'Y1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Electrical System : Alternator (35a)
60***60Alternator A. (35a),(With Non Hardening Pulley)1
KD***57Bearing,Ball? Front1
KD***80Collar1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Electrical System : Alternator And Mounting (13a)
01***55Bolt, Mount Tube To Switch Pump1
01***25Bolt1
01***11Nut (Welded)1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Electrical System : Alternator And Mounting (35a)
01***30Bolt,(For Quick Shift) (Mitsubishi)1
01***30Bolt1
01***23Washer,(A)(W/After Cooler)(S6d155-4b)2
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Komatsu : 6d125-1ee(S/N 21811-Up) : Electrical System : Starting Motor (11kw)(#38123-)
60***12Starting Motor Ass'Y,(11kw)1
SD***X9Switch Ass'Y,Engage1
SD***X0Bearing,Ball1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Electrical System : Starting Motor (7.5kw)
60***30Starting Motor Ass'Y,(7.5kw)1
KD***60Shift Lever Assembly1
KD***40Spring,Spring4
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Komatsu : 6d125-1ee(S/N 21811-Up) : Electrical System : Starting Motor And Mounting (11kw)(#38123-)
01***40Bolt,(With Center Guard)3
66***10Gasket,Starting Motor1
(6***2)Starting Motor Ass'Y,(11kw)(See Fig.0662a)1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Electrical System : Starting Motor And Mounting (7.5kw)
01***40Bolt,(With Center Guard)3
66***10Gasket,Starting Motor1
(6***0)Starting Motor Ass'Y,(7.5kw) (See Fig.0661a)1
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Engine Kit
Komatsu : 6d125-1ee(S/N 21811-Up) : Engine Kit : Gasket Kit
02***43O-Ring,Water Manifold6
07***15O-Ring,(For Low Speed) (D40pf)1
07***25O-Ring,Injection Pump Mounting1
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Fuel System
Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Filter And Piping
01***25Bolt,(For Canvas Canopy?Head Guard)2
01***30Bolt,(For Quick Shift) (Mitsubishi)4
01***35Bolt,(For Quick Shift) (Mitsubishi)2
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Injection Pump (Coupling)(#21965-)
ND***30Block,Coupling2
ND***10Flange,Coupling1
ND***50Bolt1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Injection Pump (Feed Pump)(#21965-)
ND***40Washer? 1mm,Plate1
ND***70Washer,Union4
ND***10Spring, Check Valve2
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Injection Pump (Governor) (1/2)(#21965-29456)
ND***40Plate,Thrust1
ND***40Plug,Screw1
ND***50Washer? 0.3mm0
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Injection Pump (Governor) (1/2)(#29457-)
ND***40Plate,Thrust1
ND***80Pin,Stop1
ND***40Plug,Screw1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Injection Pump (Governor) (2/2)(#21965-29456)
ND***20Washer? 1.0mm,Cover Plate2
ND***10Seal,Oil1
ND***50Packing,Rubber Plate1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Injection Pump (Governor) (2/2)(#29457-)
ND***20Washer? 1.0mm,Cover Plate2
ND***90Seal,Oil1
ND***40O-Ring1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Injection Pump (Pump) (1/2)(#21965-29456)
61***60Injection Pump A1
ND***50Ring,Adjust1
ND***80O-Ring1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Injection Pump (Pump) (1/2)(#29457-)
61***20Injection Pump A1
61***21Injection Pump A1
ND***50Ring,Adjust1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Injection Pump (Pump) (2/2)(#21965-29456)
ND***70O-Ring6
ND***71Rack,Control1
ND***50Seat,Spring? Lower6
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Injection Pump (Pump) (2/2)(#29457-)
ND***30Sleeve,Control6
ND***20Shim? 0.3mm0
ND***70O-Ring6
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Injection Pump And Piping(#21965-29456)
01***75Bolt,(See Fig.0142)4
01***30Bolt1
01***25Bolt,(For Canvas Canopy?Head Guard)6
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Injection Pump And Piping(#29457-)
01***75Bolt,(See Fig.0142)4
01***30Bolt1
01***20Bolt,(For Quick Shift) (Mitsubishi)1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Nozzle And Spill Pipe(#21811-29456)
01***45Bolt, Divider Valve Mounting12
07***65O-Ring,Cylinder Block6
07***12Gasket,Mechanical Pump Piping2
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Fuel Nozzle And Spill Pipe(#29457-)
01***45Bolt, Divider Valve Mounting12
07***65O-Ring,Cylinder Block6
07***12Gasket,Mechanical Pump Piping2
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Water Separator (For 13a Alternator)
07***60O-Ring,(For Pc750?800?1800) (A2610)1
60***00Water Separator A.,(4d105-5h? 4d105-5t)1
60***60Plug,Drain (4d105-5h? 4d105-5t)1
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Komatsu : 6d125-1ee(S/N 21811-Up) : Fuel System : Water Separator And Mounting (For 35a Alternator)
01***25Bolt,Without Revolution Sensor2
01***20Bolt,(For Quick Shift) (Mitsubishi)2
01***16Washer,(For 35a Alternator)2
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Lubricating Oil System
Komatsu : 6d125-1ee(S/N 21811-Up) : Lubricating Oil System : Lubricating Oil Cooler
01***25Bolt,Without Revolution Sensor2
01***25Bolt,(For Canvas Canopy?Head Guard)13
01***65Bolt,(Except Japan)2
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Komatsu : 6d125-1ee(S/N 21811-Up) : Lubricating Oil System : Lubricating Oil Filter
01***25Bolt,(For Canvas Canopy?Head Guard)2
01***30Bolt,(For Quick Shift) (Mitsubishi)4
01***35Bolt,(For Quick Shift) (Mitsubishi)2
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Komatsu : 6d125-1ee(S/N 21811-Up) : Lubricating Oil System : Lubricating Oil Piping
01***16Bolt, Battery To Frame Ground Wire Attaching1
01***35Bolt,(For Quick Shift) (Mitsubishi)2
01***50Bolt,(With Service Valve R.H.)2
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Komatsu : 6d125-1ee(S/N 21811-Up) : Lubricating Oil System : Lubricating Oil Pump And Suction Pipe
01***25Bolt,(Without Auto Priming System)4
01***20Bolt,(Large Capacity Type) (Std)2
01***25Bolt,(Sandy? Dusty Terrain Spec.)5
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6D125-1EE(S/N 21811-UP) serial number reference

On this engine the ID plate is riveted to the left side of the cylinder block (opposite the exhaust manifold); it lists the engine model, arrangement number, and serial number, and if it's missing or unreadable the serial is also stamped into the block near that same spot. Read the model line as '6D125-1' (family/displacement) plus a trailing two-letter arrangement suffix like 'EE' that marks the specific machine fitment, not a chassis PIN code; the number after it (21811-and-up here) is the engine's own running serial count, separate from the host dozer's chassis serial number.

PrefixIdentifies
EEKomatsu D58P-1 / D58P-1B crawler dozer (wide-gauge / LGP-style undercarriage)

Frequently asked questions

What engine powers this machine?

It runs the Komatsu 6D125-1EE, an 11.0-liter (125 x 150 mm bore/stroke), water-cooled, mechanically-governed in-line six-cylinder diesel from the 6D125-1 family, at engine serial 21811-and-up. A confirmed horsepower rating for this exact suffix and serial break is not independently published; check your engine data plate or your dealer for the exact factory rating on your unit.

What is the operating weight of the machine this engine powers?

Parts-fitment records point most consistently to the Komatsu D58P-1 / D58P-1B low-ground-pressure crawler dozer as the host for this engine serial break; published operating weight for that chassis ranges roughly 12.6-15.7 t (about 27,800-34,600 lb) depending on source and blade/undercarriage configuration. This engine family was also fitted to other Komatsu dozer and motor grader chassis of the same era with different weight classes, so confirm your exact machine's weight from its own chassis data plate rather than by engine model alone.

What replaced this engine?

Within the same D58P-1/D58P-1B dozer lineup, Komatsu parts records show the 6D125-1EE was followed by the 6D125E-2 series, a revised version of the same 11.0-liter block. The broader 6D125-1 mechanically-governed generation was eventually superseded across Komatsu's line by its electronically-controlled 6D125/SAA6D125E engine family used in later excavators, loaders, and graders, though that is a separate engine generation rather than a direct running change of this block.

What 6D125-1EE(S/N 21811-UP) owners discuss

What's the most common complaint about oil consumption and smoke on this engine?
Owners and mechanics report engine oil consumption climbing over time, tied to worn piston rings and cylinder liners rather than one bad part. It shows up as light blue-grey smoke under load that doesn't clear at idle. Liner glazing from short duty cycles or stretched oil-change intervals is the root cause mechanics point to most often, not a design flaw in the block. An inframe rebuild with new rings and honed or replaced liners resolves it in the cases reported. Have your dealer verify liner and ring wear with a bore gauge before committing to a full inframe overhaul.
The engine idle speed keeps surging up and down. Is that normal for this engine?
This engine runs a mechanical, flyweight-type governor on its inline injection pump, not an electronic one, so idle hunting is a known quirk once the governor or pump wears or falls out of adjustment. Surging only at idle usually points to the low-idle stop needing adjustment. Surging under load points to weak governor spring tension or actual wear inside the pump. If surging continues after adjustment, the injection pump needs to come off for inspection. Have your dealer verify governor and pump settings before assuming a full pump rebuild is needed.
What usually causes this engine to run hot?
Techs work through the same short list every time: a radiator core clogged with dust and debris, a slipping or worn fan belt, a thermostat stuck closed, or a water pump losing circulation. In dusty sites a plugged radiator core gets called out most often as the cause, ahead of any internal engine problem. A water pump on its way out typically weeps coolant at the pump housing before it fails outright, so a fresh coolant seep near the front of the block is worth chasing early. Have your dealer verify the actual cause with a pressure test and coolant flow check rather than replacing parts on a guess.
Is hard cold-starting and extra white smoke on cold mornings normal for this engine?
Yes, within reason. This is a mechanically governed, pre-electronic diesel, so there is no ECM-driven cold-start strategy; starting aid is limited to glow plugs or an ether/starting-fluid system where fitted. Cold-weather starting depends heavily on battery condition, fuel quality in cold temperatures, and injection timing being correct. Harder starts and more white smoke on cold mornings than on later electronically controlled diesels is expected for this engine generation, not a fault by itself. Hard starting that persists once engine and ambient temps have warmed up points to injection timing drift or worn injectors, not the cold-start aid.
What electrical or sensor issues come up on this engine?
The electrical side is simple on a mechanical-injection engine like this one: starting and charging circuit, a coolant temperature switch and oil pressure switch feeding gauges or warning lights, and a glow-plug or intake-heater relay circuit where fitted. Reported issues are mostly basic, a sender or gauge reading wrong rather than any complex fault-code diagnosis. A false high-temperature or low-oil-pressure warning is usually traced to a bad switch or a corroded connector, not an actual engine problem. Treat any warning light as real until a manual gauge check proves otherwise.
What wear patterns should I expect on the machine this engine is fitted to?
The host chassis for this engine varies by application; it has been fitted to dozer chassis and motor-grader chassis, so the typical high-wear component depends on which machine you actually have. On dozer-size machines in this class, undercarriage is the main recurring wear item, with life swinging widely by ground conditions and maintenance rather than the engine, roughly 3,000 to 4,500 hours before a turn is typical, sometimes far less in abrasive ground. On a motor-grader chassis, blade-related wear, moldboard, circle, and drawbar, is the equivalent high-wear item instead. Confirm your exact chassis type with your dealer so the right wear intervals apply.
What should I check when buying a used machine with this engine?
Pull an oil sample and check for metal and coolant contamination. Watch for blue-grey exhaust smoke under load, a sign of ring and liner wear. Check coolant for an oil sheen and inspect around the water pump for weep-hole leakage. Listen for governor hunting or surging at idle and under light load. Check the exhaust manifold and turbocharger, where fitted, for shaft play and oil residue at the seals. Confirm cold starting doesn't depend heavily on ether. Ask for maintenance records and compare hours against visible wear, since oil-change interval is the single biggest factor reported for ring and liner life on this engine family. Have your dealer verify compression and injection pump condition before finalizing the purchase.

Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.

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