Komatsuengine(no series)

Komatsu 4D95L-1AA-7(S/N 49965-UP)

Maintenance schedule, common problems & OEM parts breakdown

Search live 4D95L-1AA-7(S/N 49965-UP) parts

The 4D95L-1AA-7 (S/N 49965-UP) is a bare Komatsu industrial diesel engine, not a complete machine: a naturally aspirated, water-cooled, inline 4-cylinder diesel displacing 3.26 L on a 95 mm bore and 115 mm stroke, rated in the roughly 40 kW (about 54 hp) class. It runs a mechanical, all-speed governed injection pump and mechanical glow-plug preheat, with no ECM and no electronic fault codes. Komatsu's engine-to-equipment documentation ties this specific -7 running-change variant, effective at engine S/N 49965 and up, to the PC70-6 / PC70-6S mini excavator (equipment S/N 34101-Up), placing it in the roughly 5-6 tonne mini excavator class. The same 49965-UP serial break also covers the related 1AA, 1BB and 1CC engine codes fitted to the PC60-6, PC60L-6 and PC90-1 excavators, though those pair with the base engine rather than this -7 suffix. No confirmed direct predecessor or successor exists specifically for this -1AA-7 running change; it sits within Komatsu's long-running 95-series engine family that later continued into electronically governed generations.

The step from the base 1AA/1BB engine to this -7 suffix marks a running production change within the same 49965-UP serial break, consistent with the kind of injection or governor calibration refinement Komatsu made mid-cycle on its 1990s compact excavator line, though the exact nature of the change is not spelled out in available documentation. What keeps this engine relevant in the used and parts market today is its simplicity: no ECM, no aftertreatment, and a mechanical fuel system that shops can diagnose with gauges, compression tests, and injector-line checks rather than a diagnostic laptop. Rebuild kits and parts for the wider 1AA/1AA-7/1BB/1CC engine family remain available, which keeps older PC60-6 and PC70-6-class excavators economical to keep running or to part out. Buyers shopping this engine code should confirm the exact suffix and serial break on the nameplate before assuming parts interchange with the base 1AA/1BB or the 1CC engine, since injection and governor calibration can differ across these running changes even though the block family is shared.

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 4D95L-1AA-7(S/N 49965-UP) specifications

Engine

Base engine modelKomatsu 4D95L-1 series, naturally aspirated in-line 4-cylinder diesel. This job covers the 4D95L-1AA-7 running-change build, effective at engine serial no. 49965 and up, part of the same serial-break group as the 1AA, 1BB and 1CC variants.
Cylinders / configuration4 cylinders in-line, water-cooled, direct injection diesel
Displacement3.26 L (95 mm bore x 115 mm stroke)
Net powerApprox. 40 kW (about 54 hp) class rating documented for the 4D95L-1 base engine as fitted to its host excavator range. An exact certified figure specific to the -1AA-7 running change is not separately published — confirm against the engine nameplate or with your dealer.
AspirationNaturally aspirated, non-turbo, non-aftercooled. Turbocharged / much higher output figures (over 100 kW) turn up in some general aggregator listings, but those belong to unrelated engines in the wider 95-series family (6-cylinder S/SA-prefixed variants) and do not apply to this 4-cylinder bare engine.
Emissions tierPre-dates EPA/EU nonroad emissions tier regulation; this is a 1990s-era mechanically governed diesel with no certification tier.

Weights

Bare engine assembly weightRoughly 320 kg dry, as generally documented for the 4D95 engine family. Not independently confirmed for this specific -1AA-7 serial break — verify the exact figure with your dealer.
Shipping weightNot published for this configuration in available literature.
Ground pressureNot applicable — this is a bare engine, not a complete machine.

Dimensions

Overall length / width / heightNot published for this exact engine configuration in the sources checked. Consult the Komatsu 4D95L-1 series shop manual or your dealer for certified installation dimensions.
Other class-relevant dimensionsNot applicable in the usual sense — as a bare engine assembly, transport length/width/height, wheelbase and ground clearance are properties of the host machine, not this engine.

Performance

Peak torque engine speedApproximately 2100 rpm, per the host excavator's engine data.
Rated / governed speedNot separately published for this serial break. Class-typical governed speed for this engine family runs in the 2200 rpm range — confirm against the engine nameplate.
Typical host applicationKomatsu's engine-to-equipment documentation ties this specific -7 running-change variant, at engine S/N 49965 and up, to the PC70-6 / PC70-6S mini excavator (equipment S/N 34101-Up), a roughly 5-6 tonne class machine. The same serial break also covers the related 4D95L-1AA, 1BB, and 1CC engine codes fitted to the PC60-6, PC60L-6, and PC90-1 excavators, but those pair with the base engine rather than this -7 suffix.

Service capacities (summary)

Engine oil (lube system) capacityNot published for this exact engine/serial configuration in the sources checked — refer to the host machine's general specifications table or your dealer.
Cooling system capacityNot published for this exact engine/serial configuration in the sources checked — refer to the host machine's general specifications table or your dealer.
Fuel tank capacityNot applicable to the bare engine — fuel tank capacity is a function of the host machine, not this engine assembly.

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

4D95L-1AA-7(S/N 49965-UP) fluids & capacities

SystemCapacityRecommended fluid
Engine crankcase (with filter)Not confirmed for this exact serial range (49965-UP). Sibling 95-series industrial engines of this era run roughly 7 to 9 liters (1.8 to 2.4 US gal) with filter; treat as directional only, verify against the OMM or dealer for this suffix before use.Komatsu genuine engine oil (EO), API CD/CE service class. Viscosity by ambient temperature per Komatsu's standard chart for this engine class: SAE 10W-30 in temperate ranges, SAE 15W-40 for warmer climates, SAE 10W or 5W-30 in cold climates below freezing. Confirm exact grade split against the OMM chart for this serial range.
Cooling system (radiator + engine block)Not confirmed for this exact serial range. Comparable 95-series 4-cylinder diesels in this displacement class typically fall in the 4 to 10 liter (1 to 2.6 US gal) range depending on radiator size and host installation; this engine is sold bare into more than one host so system volume is host-dependent, not a fixed engine spec.Komatsu genuine coolant (AF-NAC type, permanent antifreeze/anti-corrosion, ethylene-glycol base), pre-mixed to the ratio specified for the operating climate. Do not substitute a non-Komatsu coolant without checking corrosion-inhibitor compatibility.
Fuel tankNot applicable at the engine level. This is a bare engine model; fuel tank capacity belongs to whichever host machine or genset it is installed in and is not documented for the engine itself.Komatsu-specified diesel fuel per the OMM sulfur-content and cetane guidance for the region of operation.
Transmission / powertrainNot applicable. No transmission is integral to this engine model; drivetrain fluids belong to the host machine, not documented under the bare-engine OMM.Not applicable at engine level.
Final drivesNot applicable. No final drive is integral to this engine model.Not applicable at engine level.
Hydraulic system and tankNot applicable. No hydraulic system is integral to this engine model.Not applicable at engine level.
Axles/differentialsNot applicable. No axle assembly is integral to this engine model.Not applicable at engine level.
Grease points (fittings, linkages, accessory drive)Spec only, no fill quantity documented.Komatsu genuine multi-purpose grease (lithium-based, NLGI No. 2), or equivalent EP grease for the ambient temperature range.

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

Komatsu 4D95L-1AA-7(S/N 49965-UP) maintenance schedule

Service intervalTasks
Every 10 h
  • Check engine oil level before starting; top up to the dipstick mark with the correct seasonal viscosity.
  • Check coolant level in the radiator or reserve tank; top up with Komatsu AF-NAC coolant mix.
  • Drain water and sediment from the fuel filter/water separator bowl.
  • Inspect the engine block and hose connections for fuel, oil, and coolant leaks.
  • Every 50 hours, check fan and alternator belt tension and adjust as needed.
  • Every 50 hours, check battery electrolyte level and clean terminal connections.
Every 250 h
  • Change engine oil and replace the oil filter cartridge.
  • Clean or replace the fuel filter element.
  • Check the air cleaner restriction indicator; service the outer element if flagged.
  • Test the glow plug preheat circuit for even cylinder warm-up.
  • Inspect the crankcase breather for blockage.
Every 500 h
  • Replace the fuel filter cartridge.
  • Replace or clean the air cleaner element.
  • Check alternator and starter motor mounting bolts and wiring connections.
  • Inspect drive belt condition and replace if cracked or glazed.
  • Check engine mounting bolt torque.
Every 1,000 h
  • Check and adjust valve (rocker arm) clearance.
  • Inspect fuel injection nozzles for spray pattern and opening pressure; recondition as needed.
  • Check compression across all four cylinders to track wear trend.
  • Check coolant corrosion-inhibitor concentration and top up as specified.
  • Inspect the water pump for bearing play and shaft seal leakage.
Every 2,000 h
  • Check and reset fuel injection pump timing.
  • Retorque cylinder head bolts and recheck valve clearance.
  • Replace coolant and flush the cooling system.
  • Inspect the vibration damper and engine mounts for wear or cracking.
  • Check crankcase blow-by/breather pressure as an early wear indicator.
Every 4,000 h
  • Perform an in-frame overhaul: inspect cylinder liners, rings, and main/rod bearing clearances against shop manual limits.
  • Remove and rebuild or reindex the fuel injection pump.
  • Replace injector nozzles as a matched set.
  • Resurface or replace the cylinder head if warped beyond shop manual limits; recut valve seats as needed.

Servicing the 4D95L-1AA-7(S/N 49965-UP) beyond the schedule

Predictive Maintenance & Fluid Analysis

On this naturally aspirated 4D95L-1 block, oil analysis is the earliest warning for ring and bore wear: rising fuel dilution or falling TBN flags the gradual blow-by increase owners report as normal aging, but a sharp jump means checking compression before it becomes a smoke problem. Test glow plug resistance across all four cylinders; a plug reading well outside the others predicts the rough, uneven cold-start firing this engine is known for. Track coolant AF-NAC concentration to catch corrosion before it reaches the wet cylinder liners.

Corrective & Common Repairs

Rough running or black smoke under load traces almost always to the mechanical rotary injection pump losing timing or delivering unevenly between cylinders; crack each injector line with the engine running to isolate the offending cylinder before committing to a pump rebuild. A no-crank condition with a good battery often comes down to a failed alternator diode holding the starting safety relay open; unplugging the alternator's small connector is the standard field check. On the PC70-6 host, swing motor and final drive seal leaks are the other frequent complaint.

Overhaul & Rebuild Points

At high hours, plan an in-frame overhaul around this engine's four-cylinder wet-liner architecture: measure liner bore, ring end-gap, and main/rod bearing clearance against shop manual limits before choosing between an inframe kit and a full block rebuild. Pull the injection pump for a bench rebuild or reindex rather than field-adjusting timing, since rotary pump wear on this generation shows up as delivery imbalance an injector-line test alone cannot fully correct. Replace injector nozzles as a matched set; resurface or replace the cylinder head if flatness is out of spec.

Seasonal & Environment Servicing

This engine's glow-plug preheat cycle matters more in cold weather than extended cranking; run the full 20-30 second cycle and repeat once before starting, since a weak plug leaves one cylinder cold and causes rough, smoky starts. Switch oil viscosity with the season per Komatsu's chart for this class: SAE 10W-30 in temperate weather, 15W-40 in hot climates, 10W or 5W-30 below freezing. Check coolant AF-NAC concentration before winter. Being naturally aspirated with no charge-air margin, service the air cleaner more often in hot, dusty environments.

4D95L-1AA-7(S/N 49965-UP) common service parts

Part numberPart
07281-00197Clamp,(With Pre-Fuel Filter)Check fitment →
600-311-1190Plate? Caution,Fuel FilterCheck fitment →
600-311-7440Cartridge,Fuel FilterCheck fitment →
6204-73-6200Fuel Filter Ass'YCheck fitment →
09637-30161Plate? Instruction,Air Cleaner (Single Element)Check fitment →

Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.

All 4D95L-1AA-7(S/N 49965-UP) assemblies by section

Every catalogued assembly group for the Komatsu 4D95L-1AA-7(S/N 49965-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Cooling System
Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cooling System : Water Pump And Cooling Fan
01***16Screw5
01***20Screw2
01***45Bolt6
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Cylinder Block
Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Block : Camshaft And Tappet
01***20Screw2
04***16Fitting Wedge1
62***31Thrust Washer1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Block : Crankshaft
61***20Bolt1
62***00Main Metal Ass'Y5
62***00Thrust Metal Ass'Y1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Block : Cylinder Block
01***14Bolt2
01***20Bolt,(For Japan Pc200)1
04***20Pin,Dowel (Welded)2
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Block : Flywheel And Flywheel Housing
01***30Bolt6
01***30Bolt - Lower Oil Cooler Outlet Tubemounting11
07***15Plug,(Used When Without Heater)1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Block : Front Cover And Gear
01***70Bolt,(For 75a Alternator)1
01***16Bolt2
01***16Screw2
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Block : Oil Pan
01***14Bolt,(W/Joy Stick Str.)(W/O Heater)24
07***16Gasket,(For Pc750-6) (See Fig.A2110)1
62***11Pan,Oil1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Block : Piston And Connecting Rod
04***12Ring, Snap8
62***01Piston Ring Ass'Y,Per Cylinder4
62***02Piston Ring Ass'Y,Per Cylinder4
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Cylinder Head
Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Head : Air Cleaner (Double Element Type)(#59833-)
04***10Ring,See Fig. K4010-65a01
09***61Plate? Instruction,(Japanese-English) (Not Shown)1
09***61Plate? Instruction,Air Cleaner (Single Element)1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Head : Air Cleaner (Single Element Type)
04***10Ring,See Fig. K4010-65a01
09***61Plate? Instruction,(Japanese-English)1
60***40Element Ass'Y,(Double Element)(Not Shown)1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Head : Air Intake Manifold And Connection
01***25Stud1
01***12Bolt,(With Speedometer)4
01***25Bolt,(With Corrosion Resistor)3
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Head : Cylinder Head
01***20Bolt, Hose Clamps (Inlet And Return Line Hoses)2
01***25Bolt, Mount Engine Oil Drain To Fuel Tank2
01***32Washer, (Without Emergency Steering)17
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Head : Cylinder Head Cover
61***10Cap, Oil Filler1
61***20Screw3
61***30Washer,(B)3
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Head : Exhaust Manifold And Muffler
01***25Grub Screw4
01***25Bolt, Mount Engine Oil Drain To Fuel Tank2
01***45Bolt, Bracket Mounting7
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Head : Exhaust Manifold And Muffler (With 35a Alternator)(#69608-)
01***25Grub Screw5
01***25Bolt, Mount Engine Oil Drain To Fuel Tank2
01***45Bolt, Bracket Mounting7
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Cylinder Head : Rocker Arm
01***65Bolt,(For Alternator Bracket Mount)5
61***30Circlip2
62***00Shaft Ass'Y1
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Electrical System
Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Electrical System : Alternator (15a)(#102171-)
60***50Alternator A. (15a)1
KD***70Cover1
KD***30Retainer1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Electrical System : Alternator (15a)(#49965-102170)
60***70Alternator A. (15a),(See Fig.0641)1
KD***70Cover1
KD***30Retainer1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Electrical System : Alternator (25a)(#55966-)
60***20Alternator A. (25a),(With Non Hardening Pulley)1
KD***57Bearing,Ball? Front1
KD***11Rear Bracket Ass'Y1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Electrical System : Alternator (35a)(#69608-)
60***20Alternator A. (35a),(With Non Hardening Pulley)1
KD***57Bearing,Ball? Front1
KD***80Collar1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Electrical System : Alternator And Mounting (15a)
01***25Bolt,(With Corrosion Resistor)4
01***65Bolt,(For 35a? 25a Alternator)1
01***95Bolt1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Electrical System : Alternator And Mounting (25a) (With Safety Cover)(#62826-)
01***40Bolt,(Cold Weather Spec.)1
01***25Bolt,(With Corrosion Resistor)3
01***60Screw1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Electrical System : Alternator And Mounting (25a)(#59236-)
01***35Bolt,(Cold Weather Spec.)1
01***25Bolt,(With Corrosion Resistor)3
01***60Screw1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Electrical System : Alternator And Mounting (35a)(#69608-)
01***30Bolt,(For Trimming Dozer)1
01***25Bolt,(With Corrosion Resistor)3
01***70Bolt,(For 50a Alternator)1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Electrical System : Starting Motor (2.8kw)
60***10Starting Motor Ass'Y,(2.8kw)1
KD***60Bracket,Center1
KD***50Stopper,Piston1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Electrical System : Starting Motor And Mounting (2.8kw)
01***14Bolt,(With Corrosion Resistor)1
01***30Bolt2
07***95O-Ring,Transmission Strainer1
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Engine Kit
Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Engine Kit : Gasket Kit
01***12Washer,Lock (Noise Suppression Spec.) (K2)1
07***65O-Ring,Injection Pump Case1
07***95O-Ring,Transmission Strainer1
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Fuel System
Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Fuel System : Fuel Filter And Piping
01***20Bolt2
07***12Gasket,(Without Air Compressor Type) (K1)6
07***14Bolt,Joint2
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Fuel System : Fuel Injection Pump (Feed Pump)
DK***20Bolt, Joint1
DK***00Valve,Check2
DK***20Pump,Priming1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Fuel System : Fuel Injection Pump (Governor) (1/2)
DK***00Shim? 2.00mm,(High Altitude Spec.)0
DK***00Adapter1
DK***00Nut,Lock1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Fuel System : Fuel Injection Pump (Governor) (2/2)
DK***40Gasket,Air Compressor2
DK***00Nut,Cap1
DK***20Cover1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Fuel System : Fuel Injection Pump (Pump) (1/2)
62***10Injection Pump A1
DK***30Bearing0
DK***20Shim, 1.40mm; Was Dk029311-7220, Shim? 1.4mm0
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Fuel System : Fuel Injection Pump (Pump) (2/2)
DK***40Shim? 0.50mm, Shim, 0.50mm; Was Dk029311-00400
DK***90Shim? 0.25mm, Shim, 0.25mm; Was Dk029311-05900
DK***00Sleeve,Control4
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Fuel System : Fuel Injection Pump And Piping
01***35Stud4
01***12Bolt2
01***25Screw2
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Fuel System : Fuel Nozzle And Spill Pipe
01***35Bolt, Mount Bracket To Floor4
01***10Bolt1
07***10Tube,(See Fig.0421-14)3
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Lubricating Oil System
Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Lubricating Oil System : Lubricating Oil Cooler(#57338-)
01***25Bolt,(With Corrosion Resistor)4
01***30Bolt,(Water Separator Spec.)7
01***50Bolt,(With Corrosion Resistor)1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Lubricating Oil System : Lubricating Oil Filter
60***41Cartridge,Engine Oil Filter (D31s)1
60***20Plate? Caution,(Italian-English)1
60***50Plate? Caution,(Russian-English)1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Lubricating Oil System : Lubricating Oil Filter (With Oil Cooler)(#49969-)
60***41Cartridge,Engine Oil Filter (D31s)1
60***20Plate? Caution,(Italian-English)1
60***50Plate? Caution,(Russian-English)1
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Komatsu : 4d95l-1aa-7(S/N 49965-Up) : Lubricating Oil System : Lubricating Oil Pump And Suction Pipe
01***12Bolt,(See Fig.0501)1
01***16Screw6
01***25Bolt,(With Corrosion Resistor)1
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4D95L-1AA-7(S/N 49965-UP) serial number reference

The engine identification plate is riveted to the block, usually on the rocker-cover side or the flywheel housing, and states the full engine model code (4D95L-1AA-7) plus the engine serial number; the S/N 49965-UP break marks where this running-change variant started in production. The engine serial break does not by itself name the host machine — Komatsu ties a given engine variant to one or more equipment models with their own separate equipment serial ranges, so confirm the actual chassis by reading the machine's own PIN/serial plate (on the frame near the operator's step or under the cab) and cross-checking both serial numbers against a parts lookup.

PrefixIdentifies
PC70-6 / PC70-6SMini excavator host (confirmed primary application)

Frequently asked questions

What engine powers this model?

This page covers the engine itself: a Komatsu 4D95L-1AA-7, effective at engine serial no. 49965 and up. It is a naturally aspirated, water-cooled, inline 4-cylinder diesel displacing 3.26 L on a 95 mm bore and 115 mm stroke, rated in the roughly 40 kW (about 54 hp) class, with a mechanical fuel-injection pump and no electronic engine controls.

What is the operating weight?

Operating weight is not documented at the bare-engine level for this exact serial range; weight is a property of the host machine, not the engine assembly. Where confirmed installed, this engine powers the Komatsu PC70-6 / PC70-6S mini excavator, which falls in the roughly 5-6 tonne mini excavator class. Confirm the exact figure against the machine's own spec plate or your dealer.

What replaced this engine?

No confirmed direct successor is documented specifically for this -1AA-7 running change. It belongs to Komatsu's 95-series diesel family, which continued in later PC60-6/PC70-6-class excavators through electronically governed 4D95LE and SAA6D95-generation engines, but no source ties a specific replacement model to this exact suffix and serial break.

What 4D95L-1AA-7(S/N 49965-UP) owners discuss

Does owner/mechanic discussion online call out this exact 4D95L-1AA-7 (S/N 49965-UP) engine specifically?
Not really. Community discussion treats this as part of the wider 4D95L-1 family (1AA, 1AA-7, 1BB, 1CC share the same inframe rebuild kit) rather than singling out the AA-7 suffix or this serial break. Most real-world reports reference the engine by the excavator it sits in - PC60-6, PC70-6, PC75UU-1/2, PC100-6, PC120-6, PC130-6 - rather than by engine suffix. Treat suffix-specific claims with caution and confirm anything critical against the shop manual for this exact configuration.
What do owners say about cold starting this engine?
Consistent theme: preheat matters more than cranking longer. Run the glow plug cycle a full 20-30 seconds before cranking, and repeat once if it doesn't catch. A weak or dead glow plug leaves one cylinder cold, giving rough, uneven firing, extended cranking, and white smoke until the block warms up. A quick bench check is comparing resistance across all glow plugs - a plug reading well above the others, or open/shorted, is the bad one. Cheap, common fix once located.
What's the usual cause when this engine runs rough or smokes black under load?
Owners and shops consistently point to the mechanical (rotary-type) injection pump: timing drift and uneven fuel delivery between cylinders show up as rough idle, hard starting, black smoke, and a flat loss of power under load. The standard diagnostic is to crack each injector line one at a time with the engine running - cylinders that don't change the idle when cracked are the suspect ones. Isolating it that way before paying for a full pump rebuild or reindex saves time. Because pump timing affects both performance and emissions compliance, have your dealer or an injection shop verify and reset timing rather than eyeballing the marks.
Is rising oil consumption and light exhaust smoke expected as this engine ages?
Yes, and mechanics treat it as a normal wear progression rather than a red flag by itself. As rings and bores wear on an engine of this displacement and era, blow-by increases gradually, oil consumption climbs, and a haze of exhaust smoke appears under load, often with a mild loss of power. The general advice is to track oil-add intervals and do a compression or blow-by check before assuming it's just an injection or turbo issue - on this naturally aspirated engine, ruling out ring/bore wear first avoids chasing the wrong problem.
What wear items come up most for the small excavators this engine powers?
On the PC60-6/PC70-6/PC75UU class machines this engine is commonly paired with, the recurring complaints are swing motor and gearbox seal leaks, plus a worn groove on the swing pinion shaft where the seal rides (often repaired with a speedy-sleeve rather than a full shaft replacement). Final drive/travel motor seals are the other frequent leak point. These are wear items tied to the excavator chassis, not the engine itself, but they're the most-discussed maintenance items on machines carrying this engine.
What electrical/charging issues show up on these machines?
The recurring one is a failed diode inside the alternator. On these charging circuits, a bad alternator diode can leave the starting safety relay open, so the starter won't engage even though the battery and solenoid check out fine. The standard field test is to unplug the alternator's small connector and see if the engine cranks and starts with it disconnected - if it does, the alternator is the suspect. Because this sits in the starting safety-interlock circuit, have your dealer verify the wiring and relay logic before permanently bypassing anything.
What should a buyer check before purchasing a used 4D95L-1AA-7 (S/N 49965-UP) engine or a machine carrying it?
Start with soot and leaks around the top of the engine and dark, thick oil in the fill - both point to deferred maintenance. Run it under load and watch for black smoke or a power sag that suggests injection pump timing drift, and listen for rough or uneven firing that could be a weak glow plug or an injector problem. Check oil consumption history if available, since some smoke and oil use is normal wear for an engine this age but a sharp increase is not. If buying the excavator it's mounted in, also check the swing motor and final drive for seal leaks, and the undercarriage for wear, since those carry a large share of this machine class's upkeep cost. Parts and rebuild kits for this engine generation are still available but not cheap, so confirm what documented service history exists.

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

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