Komatsu 4D84E-3C(S/N 00000-UP)
Maintenance schedule, common problems & OEM parts breakdown
The Komatsu 4D84E-3C engine is a compact, water-cooled, 4-stroke diesel powerplant designed for utility and mini-excavator applications. It is primarily fitted to the Komatsu PC50UU-2 mini excavator, specifically for units with serial numbers starting from 14993. This engine serves as the power source for machines in the compact class, typically operating in the 10,000 to 20,000 lb weight range. The 4D84E-3C succeeded earlier 3-cylinder variants in the 68E-88E series lineup, providing a reliable, fuel-efficient solution for tight-access jobsites. Configurations are limited to the specific emissions and mounting requirements of the PC50UU-2 platform.
Across the 68E-88E series generations, the transition to the 4D84E-3C marked a shift toward stricter emissions compliance and improved torque characteristics for mini-excavators. The machine remains significant in the used and parts market because the PC50UU-2 is a high-volume utility unit with widespread global deployment. As these machines age, the demand for 4D84E-3C specific components—such as cylinder heads, fuel injectors, and turbochargers—remains steady. The engine's compact design and direct-injection system make it a common target for rebuild and remanufacturing, ensuring long-term parts availability for this specific serial range.
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 4D84E-3C(S/N 00000-UP) specifications
Engine
| Model | 4D84E-3C |
| Application | Komatsu PC50UU-2 (S/N 14993 and up) |
| Type | Water-cooled, 4-stroke, turbocharged diesel |
| Cylinders | 4 in-line |
| Displacement | 4.2 liters |
| Bore | 94 mm (3.70 in) |
| Stroke | 100 mm (3.94 in) |
| Emissions Tier | Tier 4 Final / EU Stage V |
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 |
| Digging Force | Not documented for this exact serial range — verify with your dealer |
Service capacities (summary)
| Engine Oil Capacity | Not documented for this exact serial range — verify with your dealer |
| Cooling System Capacity | Not documented for this exact serial range — verify with your dealer |
| Hydraulic System Capacity | Not documented for this exact serial range — verify with your dealer |
| Fuel Tank Capacity | 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 4D84E-3C(S/N 00000-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 4D84E-3C(S/N 00000-UP) beyond the schedule
Predictive Maintenance & Fluid Analysis
Utilize Komatsu Oil Wear Analysis (KOWA) at every 500-hour interval to monitor iron, copper, and lead wear metals in the engine oil. Check coolant pH and SCA concentration levels to prevent corrosion in the 4D84E-3C’s water-cooled block. Monitor hydraulic oil particle count and viscosity to detect pump wear early. Track fuel dilution and soot levels in the oil to adjust drain intervals based on actual engine load rather than fixed hours. Use KOMTRAX telematics to correlate high-load hours with fluid degradation rates.
Corrective & Common Repairs
Address fuel system issues by inspecting the direct injection pump and injector nozzles for leakage or clogging, common in high-hour 4D84E-3C units. Replace worn turbocharger seals if excessive blue smoke or oil consumption occurs. Check the water pump impeller for erosion if coolant flow drops. Inspect the air filter housing seals to prevent dust ingestion that accelerates cylinder liner wear. Verify electrical connections at the alternator and starter, as vibration can loosen terminals in the compact PC50UU-2 chassis.
Overhaul & Rebuild Points
Plan for a major overhaul when compression drops below specification or oil pressure falls despite new filters. Measure cylinder bore wear and replace piston rings if blow-by increases significantly. Inspect the crankshaft main and rod bearings for scoring or excessive clearance. Replace the cylinder head gasket if coolant leaks into the combustion chamber or oil gallery. Recondition the valve seats and guides if valve clearance cannot be maintained. Replace the turbocharger if shaft play exceeds limits or blades are damaged.
Seasonal & Environment Servicing
In cold climates, ensure the coolant mixture provides adequate freeze protection for the 4D84E-3C’s cooling system. Use lower viscosity engine oil during startup to reduce wear in cold conditions. In dusty environments, inspect the air filter restriction indicator more frequently and clean the radiator fins daily to prevent overheating. In high-humidity areas, drain the fuel water separator daily to prevent microbial growth. Check all hose clamps and belt tensions after seasonal temperature changes to prevent leaks or slippage.
4D84E-3C(S/N 00000-UP) common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| YM129100-55650 | Element,Fuel Filter | Fuel system service | Check fitment → |
| YM129052-55620 | Fuel Filter Ass'Y | Fuel system service | Check fitment → |
| YM102103-55520 | O-Ring,(For Fuel Filter) | Fuel system service | Check fitment → |
| YM129436-12900 | Element,Outer | Scheduled service item | Check fitment → |
| YM129436-12910 | Element,Inner | Scheduled service item | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
4D84E-3C(S/N 00000-UP) fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| CA115 | Engine crankshaft speed sensor and backup 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 sensor feedback voltage too high | Sensor malfunction or wiring issue | Verify the intake pressure sensor and wiring |
| CA123 | Intake air pressure sensor feedback voltage too low | Sensor short or airflow restriction | Check for a sensor short or an airflow restriction |
| CA428 | Fuel moisture sensor invalid voltage | Contaminated fuel supply or sensor harness issue | Ensure a clean fuel supply and check the moisture sensor harness |
| CA153 | Intake air temperature sensor feedback voltage too high | Sensor failure | Replace or test the IAT sensor |
| CA154 | Intake air temperature sensor feedback voltage too low | Sensor failure | Replace or test the IAT sensor |
| CA441 | Battery voltage too low | Weak battery or charging system failure | Replace the alternator or battery; check the voltage regulator |
| CA442 | Battery voltage too high | Alternator overcharging | 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.
4D84E-3C(S/N 00000-UP) attachments & work tools
Excavator Work Tools
The Komatsu 4D84E-3C engine is specified for the PC50UU-2 crawler excavator starting from serial number 14993. This machine class typically utilizes standard excavator buckets and hydraulic breakers. Factory configurations for this size class include standard digging buckets and optional heavy-duty rock buckets. Guarding options often include side cutters and tooth adapters for wear protection.
Loader Work Tools
The 4D84E-3C engine powers the SK815 series skid steer loaders, including models SK815-5, SK815-5E0, SK815-5N, SK816-6, SK820-5, SK820-5N, and SK820-6. Compatible work tools include standard bucket, pallet fork, and grapple attachments. These machines utilize a skid steer quick-attach coupler system for tool interchangeability. Hydraulic kit requirements vary by tool; high-flow tools require specific hydraulic circuit configurations.
Hydraulic System Notes
The engine drives the main hydraulic pump for the attached machinery. Recommended fluids include Komatsu Hydraulic Oil (HO) for the system and Komatsu Super Coolant AF-NAC for the engine cooling circuit. Proper fluid specification is critical for pump longevity and engine thermal management. Hydraulic arrangement notes depend on the specific machine model (excavator vs. skid steer) rather than the engine alone.
All 4D84E-3C(S/N 00000-UP) assemblies by section
Every catalogued assembly group for the Komatsu 4D84E-3C(S/N 00000-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Accessory
Komatsu : 4d84e-3c(S/N 00000-Up) : Accessory : P.P.C. Pump And Mounting(#00141-)
| YM***20 | Pump Ass'Y,Hydraulic | 1 |
| YM***64 | Bearing,Ball | 2 |
| YM***81 | Gasket (Kit) | 1 |
Cooling System
Komatsu : 4d84e-3c(S/N 00000-Up) : Cooling System : Water Pump And Cooling Fan(#00141-)
| YM***20 | Gasket,Water Pump | 1 |
| YM***02 | Screw | 4 |
| YM***02 | Screw | 1 |
Cylinder Block
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Block : Camshaft And Tappet(#00141-)
| YM***80 | Camshaft Ass'Y | 1 |
| YM***01 | Gear Ass'Y,Camshaft | 1 |
| YM***50 | Bearing, Thrust | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Block : Crankshaft(#00141-)
| YM***00 | Gear,Crank | 1 |
| YM***80 | Parallel Pin | 1 |
| YM***50 | Pulley,Crank | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Block : Cylinder Block(#00141-)
| YM***60 | Cylinder Block, Assembly | 1 |
| YM***20 | Plug,Drain(Without Oil Cooler Type) | 1 |
| YM***00 | Plug | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Block : Flywheel And Flywheel Housing(#00141-)
| YM***02 | Screw | 6 |
| YM***90 | Flywheel Ass'Y | 1 |
| YM***80 | Parallel Pin | 4 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Block : Front Cover And Gear(#00141-)
| YM***90 | Front Cover Ass'Y | 1 |
| YM***51 | Cap, Lub. Oil Supply | 1 |
| YM***52 | Bolt | 4 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Block : Oil Pan(#00141-)
| YM***30 | Spacer | 1 |
| YM***52 | Screw | 2 |
| YM***52 | Screw | 24 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Block : Piston And Connecting Rod(#00141-)
| YM***00 | Screw | 2 |
| YM***00 | Crank Pin Metal A. (Std) | 1 |
| YM***10 | Assembly, Piston (+0.25 mm) | 4 |
Cylinder Head
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Head : Air Cleaner And Mounting (Double Element Type)(#00141-)
| YM***41 | Buffle | 1 |
| YM***10 | Cap | 1 |
| YM***30 | Pan,Dust | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Head : Air Cleaner And Mounting (Single Element Type)(#00141-)
| YM***41 | Buffle | 1 |
| YM***10 | Cap | 1 |
| YM***30 | Pan,Dust | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Head : Air Intake Manifold And Connection(#00141-)
| YM***01 | Heater,Intake Air | 1 |
| YM***00 | Clamp | 2 |
| YM***00 | Manifold,Air Intake | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Head : Cylinder Head Cover(#00141-)
| YM***20 | Cover, Breather | 1 |
| YM***51 | Cap, Lub. Oil Supply | 1 |
| YM***00 | Clip,Breather Hose | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Head : Cylinder Head(#00141-)
| YM***80 | Retainer, Spring | 8 |
| YM***40 | Seal,Valve? Exhaust (Kit) | 4 |
| YM***10 | Valve,Exhaust | 4 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Head : Exhaust Manifold And Muffler(#00141-)
| YM***02 | Screw | 6 |
| YM***00 | Manifold, Exhaust | 1 |
| YM***10 | Gasket (Kit) | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Cylinder Head : Rocker Arm(#00141-)
| YM***02 | Nut,Rock | 3 |
| YM***02 | Screw | 7 |
| YM***80 | Spring | 4 |
Electrical System
Komatsu : 4d84e-3c(S/N 00000-Up) : Electrical System : Alternator (40a)(#00141-)
| YM***50 | Brush Ass'Y | 1 |
| YM***00 | Retainer,Bearing | 1 |
| YM***70 | Diode Ass'Y | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Electrical System : Alternator And Mounting (40a)(#00141-)
| YM***30 | Plate,Adjust | 1 |
| YM***02 | Nut | 1 |
| YM***02 | Nut | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Electrical System : Starting Motor (2kw)(#00141-)
| YM***50 | Pinion Ass'Y,Pinion | 1 |
| YM***20 | Housing,Center | 1 |
| YM***40 | Field Coil Ass'Y | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Electrical System : Starting Motor And Mounting (2kw)(#00141-)
| YM***52 | Bolt Plated | 2 |
| YM***02 | Nut,Rock | 1 |
| YM***00 | Washer,Spring | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Electrical System : Timer? Safety Relay And Grow Relay(#00141-)
| YM***20 | Timer,Solenoid | 1 |
| YM***10 | Relay,Stop Solenoid | 1 |
| YM***00 | Relay, Safety | 1 |
Fuel System
Komatsu : 4d84e-3c(S/N 00000-Up) : Fuel System : Fuel Filter And Piping(#00141-)
| YM***70 | Union | 1 |
| YM***00 | O-Ring (Kit) | 1 |
| YM***51 | Check Valve Ass'Y,Joint | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Fuel System : Fuel Injection Pump (Governor) (1/2)(#00141-)
| YM***40 | Lever,Control | 1 |
| YM***30 | Spacer,Lever Shaft | 1 |
| YM***02 | Nut | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Fuel System : Fuel Injection Pump (Governor) (2/2)(#00141-)
| YM***01 | Weight Assembly., Governor | 1 |
| YM***50 | Angleich Ass'Y | 1 |
| YM***00 | Washer,Spring | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Fuel System : Fuel Injection Pump (Pump) (1/2)(#00141-)
| YM***50 | Kit, Shim | 1 |
| YM***10 | Plate? Caution | 1 |
| YM***90 | Key,Woodruff | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Fuel System : Fuel Injection Pump (Pump) (2/2)(#00141-)
| YM***70 | Retainer, Spring | 4 |
| YM***00 | Rack,Control | 1 |
| YM***02 | Screw | 2 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Fuel System : Fuel Injection Pump And Piping(#00141-)
| YM***20 | Retainer, Pipe | 2 |
| YM***60 | O-Ring,Fuel Injection Pump | 1 |
| YM***02 | Nut | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Fuel System : Fuel Nozzle And Spill Pipe(#00141-)
| YM***00 | Nozzle, Assembly | 1 |
| YM***20 | Spring | 1 |
| YM***00 | Fuel Injection Nozzle, Assembly | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Fuel System : Water Separator And Piping(#00141-)
| YM***10 | Hose,(See Fig.0415-17?0416-17) | 1 |
| YM***00 | Gasket | 2 |
| YM***00 | O-Ring (Kit) | 1 |
Lubricating Oil System
Komatsu : 4d84e-3c(S/N 00000-Up) : Lubricating Oil System : Lubricating Oil Filter And Mounting(#00141-)
| YM***50 | Nut | 1 |
| YM***02 | Bolt Plated | 3 |
| YM***00 | Valve,Relief | 1 |
Komatsu : 4d84e-3c(S/N 00000-Up) : Lubricating Oil System : Lubricating Oil Pump And Piping(#00141-)
| YM***50 | Oil Pressure Transmitter | 1 |
| YM***50 | Pipe,Oil | 1 |
| YM***02 | Seal,Ring (Kit) | 2 |
Tool And Kit
Komatsu : 4d84e-3c(S/N 00000-Up) : Tool And Kit : Gasket Kit(#00141-)
| YM***60 | O-Ring,Fuel Injection Pump | 1 |
| YM***40 | Seal,Valve? Exhaust (Kit) | 4 |
| YM***20 | Gasket,Water Pump | 1 |
Frequently asked questions
What engine does the Komatsu PC50UU-2 use?
The Komatsu PC50UU-2 mini excavator uses the Komatsu 4D84E-3C engine for units with serial numbers 14993 and up.
What is the operating weight of the Komatsu PC50UU-2?
The operating weight of the Komatsu PC50UU-2 varies by configuration, typically ranging from 10,000 to 20,000 lbs.
What replaced the Komatsu 4D84E-3C engine?
The 4D84E-3C is part of the 68E-88E series lineage. Later models in the PC50UU-2 series and subsequent mini-excavator generations transitioned to newer emissions-compliant engines, such as the 4D84E-3D or 4D84E-3E, depending on the serial number break and regional regulations.
What 4D84E-3C(S/N 00000-UP) owners discuss
What are the known powertrain and hydraulic behaviors associated with the Komatsu 4D84E-3C engine series?
What undercarriage or wear patterns are typical for machines powered by this engine series?
What are the common engine quirks per the 4D84E-3C series?
What are the common electrical or sensor issues reported for this engine?
What should be checked when buying a used machine with the 4D84E-3C engine?
What safety-critical fixes require dealer verification for the 4D84E-3C?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
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