Komatsu S3D84-2J(S/N 05091-UP)
Maintenance schedule, common problems & OEM parts breakdown
The Komatsu S3D84-2J (S/N 05091-UP) is a compact crawler excavator in the mini-excavator class, designed for utility work and confined space operations. It is powered by the Komatsu 3D84 engine, a vertical, water-cooled, 4-stroke, 3-cylinder diesel unit with a displacement of 1,496 cc, producing 38 hp at 2,700 rpm. Operating weight ranges from 9,182 to 12,688 lb depending on configuration. Production years span approximately 2017 to 2025. This model succeeds earlier 3D84-powered variants and precedes newer Tier 4 Final/Stage V compliant generations. Configurations offered include standard and low-ground-pressure undercarriage options, various stick lengths, and attachment packages for hydraulic breakers or augers.
Across the S3D84 series, the primary change was the transition from earlier emissions tiers to Tier 4 Final/Stage V compliance, requiring updates to the fuel injection system and exhaust aftertreatment (KDPF/SCR). The S3D84-2J matters in the used and parts market because the 3D84 engine is mechanically simple and widely shared with Yanmar counterparts, making it a cost-effective powerplant for fleet managers. Its compact size and reliability in tight spaces ensure high demand for replacement undercarriage components, hydraulic pumps, and engine overhaul kits. The serial break at 05091-UP indicates specific catalog and parts variations that must be verified against the machine plate to ensure correct fluid capacities and filter specifications.
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 S3D84-2J(S/N 05091-UP) specifications
Engine
| Model | S3D84-2J |
| Series/Generation | S3D84 series |
| Type | Vertical, water-cooled, 4-stroke diesel |
| Cylinders | 3 |
| Displacement | 1.496 L (91.3 cu in) |
| Bore | 84 mm (3.31 in) |
| Power | 38 hp (28.3 kW) at 2,700 rpm |
| Emissions Tier | Not documented for this exact serial range — verify with your dealer |
Weights
| Operating Weight | Not documented for this exact serial range — verify with your dealer |
| Shipping Weight | Not documented for this exact serial range — verify with your dealer |
| Ground Pressure | Not documented for this exact serial range — verify with your dealer |
Dimensions
| Transport Length | Not documented for this exact serial range — verify with your dealer |
| Transport Width | Not documented for this exact serial range — verify with your dealer |
| Transport Height | Not documented for this exact serial range — verify with your dealer |
| Track Gauge | Not documented for this exact serial range — verify with your dealer |
| Ground Clearance | Not documented for this exact serial range — verify with your dealer |
Performance
| Travel Speed | Not documented for this exact serial range — verify with your dealer |
| Gradeability | Not documented for this exact serial range — verify with your dealer |
| Dig Depth | Not documented for this exact serial range — verify with your dealer |
| Bucket Capacity | Not documented for this exact serial range — verify with your dealer |
Service capacities (summary)
| Fuel Tank | Not documented for this exact serial range — verify with your dealer |
| Hydraulic System | Not documented for this exact serial range — verify with your dealer |
| Engine Oil | Not documented for this exact serial range — verify with your dealer |
| Cooling System | Not documented for this exact serial range — verify with your dealer |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
Komatsu S3D84-2J(S/N 05091-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 S3D84-2J(S/N 05091-UP) beyond the schedule
Predictive Maintenance & Fluid Analysis
Utilize KOWA fluid analysis at every 500-hour interval to monitor engine wear metals (iron, copper, lead, aluminum) and hydraulic contamination. Check coolant pH, SCA concentration, and glycol content to prevent corrosion in the 3D84 engine block. Monitor hydraulic oil particle count and viscosity to detect pump wear early. Use KOMTRAX telematics to track load frequency and fault codes, allowing proactive scheduling of filter replacements before clogging occurs. Verify DEF levels daily to ensure SCR system efficiency and prevent engine derating.
Corrective & Common Repairs
Address common 3D84 engine issues by inspecting the turbocharger YM the OEM part reference-18010 for shaft play and oil leaks. Replace fuel injectors (YM729503-53100) if rough idling or black smoke occurs. Check the oil pump for Yanmar 3TNB84 compatibility if leakage is detected. Inspect hydraulic hoses for cracks near high-vibration points on the boom and stick. Replace worn track rollers, idlers, and sprockets if undercarriage wear measurements exceed limits. Ensure the swing bearing is greased regularly to prevent noise and play.
Overhaul & Rebuild Points
Plan engine overhaul when compression drops or oil consumption exceeds limits. Use a major overhaul kit compatible with the 3D84-2/3D84N-2FA/S3D84-2J engines, including cylinder liners, pistons, and bearings. Inspect the crankshaft for wear and replace if necessary. Rebuild the hydraulic pump if flow or pressure tests fail. Check the final drive gears and seals for leakage; replace oil seals and bearings if metal particles are found in the oil. Ensure the turbocharger is replaced if shaft clearance is excessive or blades are damaged.
Seasonal & Environment Servicing
In cold weather, use Komatsu Super Coolant AF-NAC at the correct concentration to prevent freezing. Check battery charge and insulation. In hot weather, clean debris from the radiator and oil cooler fins to prevent overheating. Inspect the air filter element more frequently in dusty environments. Use Komatsu Genuine Lubricants with the correct viscosity for ambient temperatures. Check the cooling system for leaks and ensure the fan belt is tensioned properly. Drain water from the fuel separator daily in humid conditions to prevent microbial growth.
S3D84-2J(S/N 05091-UP) common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| YM129100-55650 | Element,Fuel Filter | Fuel system service | Check fitment → |
| YM129100-55621 | Fuel Filter Ass'Y | Fuel system service | Check fitment → |
| YM102103-55520 | O-Ring,(For Fuel Filter) | Fuel system service | Check fitment → |
| YM129103-35101 | Adapter,Oil Filter | Lubrication service | Check fitment → |
| YM171301-92750 | Wrench,Engine Oil Filter | Lubrication service | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
S3D84-2J(S/N 05091-UP) fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| CA115 | Engine crankshaft speed sensor and backup speed sensor failure | Faulty speed sensor, broken wiring harness, or corroded connector at the pin connector | Replace the speed sensor and verify voltage at the pin connector |
| CA111 | Internal engine controller fault | Electronic Control Module (ECM) internal failure | Replace or reprogram the ECM |
| CA451 | Common rail pressure sensor feedback value too high | Malfunction in the rail pressure sensor or actual overpressure condition | Diagnose the fuel rail pressure sensor or check pump lines |
| CA452 | Common rail pressure sensor feedback value too low | Fuel rail pressure sensor error or low pressure condition | Diagnose the fuel rail pressure sensor or check pump lines |
| CA122 | Intake air pressure sensor feedback voltage too high | Intake pressure sensor malfunction or wiring issue | Verify the intake pressure sensor and wiring |
| CA123 | Intake air pressure sensor feedback voltage too low | Sensor short circuit or airflow restriction | Check for a sensor short or an airflow restriction |
| CA153 | Intake air temperature sensor feedback voltage too high | Intake air temperature (IAT) sensor error | Replace or test the IAT sensor |
| CA154 | Intake air temperature sensor feedback voltage too low | Intake air temperature (IAT) sensor error | Replace or test the IAT sensor |
| CA441 | Battery voltage too low | Weak battery, faulty alternator, or voltage regulator issue | Replace the alternator or battery; check the voltage regulator |
| CA442 | Battery voltage too high | Faulty alternator or voltage regulator | Replace the alternator or battery; check the voltage regulator |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
S3D84-2J(S/N 05091-UP) attachments & work tools
Buckets
Standard and heavy-duty digging buckets are available for the S3D84-2J class. Typical capacities vary by configuration/series for this compact excavator size. Factory guarding options include side cutters and teeth systems to extend wear life.
Hydraulic Breakers
Hydraulic hammers are supported via auxiliary hydraulic lines. A specific breaker kit is required to route high-pressure flow to the tool. Mounting brackets and hose assemblies are model-specific to the S3D84-2J chassis.
Grapples
Material handling grapples are offered for debris and scrap applications. These tools require a dedicated hydraulic kit for rotation and closing functions. Coupler compatibility is determined by the machine's specific attachment interface.
Augers
Earth augers are available for drilling applications. They connect via the machine's quick coupler system. Hydraulic flow requirements must be verified against the S3D84-2J engine and pump output specifications.
Couplers
Mechanical and hydraulic quick couplers are standard or optional equipment. The coupler must match the specific pin spacing and hydraulic port configuration of the S3D84-2J(S/N 05091-UP). Factory configurations may include pre-wired hydraulic lines for tool engagement.
All S3D84-2J(S/N 05091-UP) assemblies by section
Every catalogued assembly group for the Komatsu S3D84-2J(S/N 05091-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Cooling System
Komatsu : S3d84-2j(S/N 05091-Up) : Cooling System : Water Pump And Cooling Fan
| YM***41 | Fan,Cooling? (Stamp Mark Jt) | 1 |
| YM***02 | Bolt Plated | 2 |
| YM***20 | Gasket,Water Pump | 1 |
Cylinder Block
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Block : Camshaft And Tappet
| YM***01 | Gear Ass'Y,Camshaft | 1 |
| YM***11 | Camshaft | 1 |
| YM***50 | Bearing, Thrust | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Block : Crankshaft
| YM***00 | Gear,Crank | 1 |
| YM***00 | Crankshaft Ass'Y | 1 |
| YM***50 | Pulley,(For Variable Pump) | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Block : Cylinder Block
| YM***60 | Cylinder Block A | 1 |
| YM***20 | Screw | 8 |
| YM***00 | Plug | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Block : Flywheel And Flywheel Housing
| YM***00 | Gear,Ring | 1 |
| YM***02 | Screw | 6 |
| YM***02 | Screw | 4 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Block : Front Cover
| YM***02 | Bolt Plated | 2 |
| YM***10 | Washer,Seal | 4 |
| YM***51 | Cap, Lub. Oil Supply | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Block : Oil Pan
| YM***40 | Oil Pan Ass'Y | 1 |
| YM***02 | Screw | 4 |
| YM***40 | O-Ring,Drain Plug | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Block : Piston And Connecting Rod
| YM***00 | Screw | 2 |
| YM***00 | Crank Pin Metal A. (Std) | 1 |
| YM***51 | Piston Ring Ass'Y,0.25mm (Os) | 1 |
Cylinder Head
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Head : Air Cleaner And Mounting
| YM***00 | Element,Outer | 1 |
| YM***80 | Seat,Rubber | 2 |
| YM***61 | Support | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Head : Air Intake Manifold And Connection
| YM***01 | Heater,Intake Air | 1 |
| YM***00 | Manifold,Air Intake | 1 |
| YM***52 | Screw | 4 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Head : Cylinder Head
| YM***30 | Valve,Exhaust | 3 |
| YM***80 | Retainer, Spring | 6 |
| YM***40 | Seal,Valve? Exhaust (Kit) | 3 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Head : Cylinder Head Cover
| YM***20 | Cover, Breather | 1 |
| YM***51 | Cap, Lub. Oil Supply | 1 |
| YM***00 | Clip,Breather Hose | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Head : Exhaust Manifold And Turbocharger
| YM***22 | Stud | 3 |
| YM***02 | Stud | 2 |
| YM***02 | Screw | 4 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Head : Muffler And Mounting
| YM***02 | Bolt Plated | 2 |
| YM***22 | Stud | 4 |
| YM***50 | Nut | 4 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Head : Rocker Arm
| YM***02 | Screw | 6 |
| YM***80 | Spring | 3 |
| YM***00 | Plug | 2 |
Komatsu : S3d84-2j(S/N 05091-Up) : Cylinder Head : Turbocharger
| YM***20 | Shield,Heat | 1 |
| YM***80 | Housing Ass'Y,Blower | 1 |
| YM***25 | Housing Ass'Y,Turbine | 1 |
Electrical System
Komatsu : S3d84-2j(S/N 05091-Up) : Electrical System : Alternator (40a)
| YM***50 | Brush Ass'Y | 1 |
| YM***00 | Retainer,Bearing | 1 |
| YM***70 | Diode Ass'Y | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Electrical System : Alternator And Mounting (40a)
| YM***02 | Nut | 1 |
| YM***50 | Bolt | 1 |
| YM***30 | Plate,Adjust | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Electrical System : Diode? Timer And Safety Relay
| YM***00 | Diode | 1 |
| YM***00 | Relay, Safety | 1 |
| YM***00 | Relay, Safety | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Electrical System : Starting Motor
| YM***50 | Pinion Ass'Y,Pinion | 1 |
| YM***20 | Housing,Center | 1 |
| YM***40 | Field Coil Ass'Y | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Electrical System : Starting Motor And Mounting
| YM***52 | Bolt Plated | 2 |
| (Y***0) | Starting Motor Ass'Y,(2kw)(See Fig.0661) | 1 |
Fuel System
Komatsu : S3d84-2j(S/N 05091-Up) : Fuel System : Engine Stop Motor And Mounting
| YM***80 | Ring,Snap | 1 |
| YM***00 | Pin,Cotter | 1 |
| YM***90 | Washer | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Fuel System : Fuel Filter And Piping
| YM***70 | Union | 1 |
| YM***00 | O-Ring (Kit) | 1 |
| YM***51 | Check Valve Ass'Y,Joint | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Fuel System : Fuel Injection Pump (Feed Pump)
| YM***50 | Gasket,(Square Type) | 1 |
| YM***00 | Feed Pump Ass'Y,(Ass'Y Supply Only) | 1 |
| YM***00 | Feed Pump Ass'Y | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Fuel System : Fuel Injection Pump (Governor)
| YM***01 | Weight Assembly., Governor | 1 |
| YM***02 | Lever Ass'Y,Stop | 1 |
| YM***10 | Pin,Stop Lever | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Fuel System : Fuel Injection Pump (Pump)
| YM***70 | Retainer, Spring | 3 |
| YM***50 | Kit, Shim | 1 |
| YM***10 | Plate? Caution | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Fuel System : Fuel Injection Pump And Piping
| YM***20 | Retainer, Pipe | 1 |
| YM***60 | O-Ring,Fuel Injection Pump | 1 |
| YM***30 | Bolt | 2 |
Komatsu : S3d84-2j(S/N 05091-Up) : Fuel System : Fuel Nozzle And Spill Hose
| YM***20 | Spring | 1 |
| YM***00 | Fuel Injection Nozzle, Assembly | 1 |
| YM***00 | Fuel Nozzle Ass'Y | 3 |
Komatsu : S3d84-2j(S/N 05091-Up) : Fuel System : Water Separator
| YM***00 | Gasket | 2 |
| YM***00 | O-Ring (Kit) | 1 |
| YM***50 | Plug,Air | 2 |
Lubricating Oil System
Komatsu : S3d84-2j(S/N 05091-Up) : Lubricating Oil System : Lubricating Oil Cooler
| YM***10 | Joint,Drain | 1 |
| YM***40 | Hose,Water | 1 |
| YM***00 | Clamp | 4 |
Komatsu : S3d84-2j(S/N 05091-Up) : Lubricating Oil System : Lubricating Oil Filter
| YM***50 | Cartridge,Engine | 1 |
| YM***51 | Cartridge | 1 |
| YM***00 | Plug | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Lubricating Oil System : Lubricating Oil Pump And Suction Pipe
| YM***50 | Oil Pressure Transmitter | 1 |
| YM***40 | Gasket,Inlet Pipe | 1 |
| YM***20 | Gasket,Lubricating Oil Pump | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Lubricating Oil System : Turbocharger Lubricating Oil Piping
| YM***01 | Pipe,Outlet | 1 |
| YM***10 | Washer,Seal | 2 |
| YM***60 | O-Ring (Kit) | 1 |
Tool And Kit
Komatsu : S3d84-2j(S/N 05091-Up) : Tool And Kit : Gasket Kit
| YM***60 | O-Ring,Fuel Injection Pump | 1 |
| YM***20 | Gasket,Water Pump | 1 |
| YM***82 | Gasket,(Not Shown) | 1 |
Komatsu : S3d84-2j(S/N 05091-Up) : Tool And Kit : Tool
| YM***50 | Wrench,Engine Oil Filter | 1 |
| YM***20 | Flex Horn (Option.) | 1 |
| YM***60 | Fuel, Wrench, Strainer | 1 |
Frequently asked questions
What engine does the Komatsu S3D84-2J use?
The Komatsu S3D84-2J uses the Komatsu 3D84 engine, a vertical, water-cooled, 4-stroke, 3-cylinder diesel engine with a displacement of 1,496 cc, producing 38 hp at 2,700 rpm.
What is the operating weight of the Komatsu S3D84-2J?
The operating weight of the Komatsu S3D84-2J varies by configuration, ranging from 9,182 lb to 12,688 lb.
What replaced the Komatsu S3D84-2J?
The Komatsu S3D84-2J was succeeded by newer generations of compact excavators compliant with Tier 4 Final/Stage V emissions standards, such as the PC series with updated engine technology and enhanced telematics.
What S3D84-2J(S/N 05091-UP) owners discuss
What engine powers the Komatsu S3D84-2J (S/N 05091-UP) and what are its core specifications?
What are the common hydraulic behaviors and failure patterns for this machine series?
What undercarriage and wear patterns are typical for this class of excavator?
What are the common electrical and sensor issues reported by owners?
What engine quirks or maintenance points are specific to the 3D84 series?
What fluids and capacities are specified for this machine?
What should you check when buying a used S3D84-2J (S/N 05091-UP)?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
Need a specific S3D84-2J(S/N 05091-UP) part?
Search live OEM part data, check fitment, and cross-reference alternatives with Heavy Parts AI.