Komatsu 1D84-1A(S/N 00101-UP)
Maintenance schedule, common problems & OEM parts breakdown
The 1D84-1A is Komatsu's own single-cylinder, direct-injection diesel of roughly 0.39 liter displacement, rated around 5.5 kW (7.4 hp) at 2800 rpm. It was the factory engine in the Komatsu PC03-1 micro crawler excavator, a sub-one-ton machine (about 0.75 t / 1,650 lb operating weight) built from 1991 into the mid-1990s for tight-access trenching and landscaping work. The 1A designation covers the earliest PC03-1 production run from engine S/N 00101-up; Komatsu carried the same block forward through in-line running changes badged 1D84-1B and then 1D84-1C on later machines in the same model. A smaller-bore sibling, the 1D75-1A, powered the companion PC02-1/PC02-1A micro excavator sold alongside it. No wheeled, generator, or dozer configuration is documented for this engine; the PC03-1 was track-only.
The step from -1A to -1C was a series of incremental production revisions, not a displacement or rated-output change; every listing for this engine family shows the same 5.5 kW (7.4 hp) at 2800 rpm regardless of dash suffix. Komatsu kept the 1D84 engine in service into the redesigned PC03-2 (1997-98, roughly 0.82-0.87 t) before dropping it for a two-cylinder 2D68E-3A on the PC03-2F generation (1999-2002), which closed out the single-cylinder line in this micro-excavator family. Very few PC03-1 units remain active today, and factory documentation for this exact serial range is thin, so most parts demand now comes from owners keeping older micro excavators running rather than fleet replacement — gaskets, injection components, and piston or liner kits for rebuild are the common ask.
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 1D84-1A(S/N 00101-UP) specifications
Engine
| Type | Single-cylinder, vertical, 4-stroke diesel |
| Cylinders | 1 |
| Displacement | approx. 0.39 L (23.7 cu in) — single-source figure, not independently cross-verified |
| Gross power | approx. 5.5 kW (7.4 hp) at 2,800 rpm — figure consistent across two independent listings for this engine family, though one ties it to the 1A/plain designation and the other to the 1C sibling; treat as representative of the 1D84 family rather than confirmed exclusive to the 1A (S/N 00101-UP) build |
| Emissions tier | Pre-emissions-regulation era design (machine platform built early 1990s); no emissions tier published |
Weights
| Host machine operating weight | approx. 0.75 t (1,653 lb) — this is the excavator's operating weight, not the bare engine's dry weight; engine-only weight not published |
| Shipping weight | Not documented for this engine — verify with your dealer |
| Ground pressure | Not published for this specific serial range |
Dimensions
| Host-machine transport width | approx. 0.81 m (2.66 ft) |
| Host-machine track gauge | approx. 180 mm (7.1 in) |
| Transport length / height | Not documented for this specific serial range — verify with your dealer |
| Ground clearance | Not documented for this specific serial range |
Performance
| Rated speed | 2,800 rpm (see Engine group for power at this speed) |
| Host-machine travel speed, swing speed, digging force | Not documented for the confirmed 1D84-1A / S/N 00101-UP pairing. Figures exist for a later, distinct micro-excavator platform that used a similarly-numbered engine, but they are not carried over here to avoid mixing unrelated model generations — verify with your dealer |
Service capacities (summary)
| Fuel tank | Not documented for this engine/serial range — verify with your dealer |
| Hydraulic system | Not applicable to the bare engine; host-machine hydraulic capacity not documented for this serial range |
| Engine oil | Not documented for this engine/serial range |
| Cooling system | Not documented for this engine/serial range; cooling method (air vs. water) not confirmed by any source checked |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
1D84-1A(S/N 00101-UP) fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Engine crankcase (with filter) | Not documented in public sources for this exact serial range — verify with your dealer or the PC03-1 operation & maintenance manual | Komatsu genuine engine oil (EO), grade per ambient temperature at time of service |
| Cooling system | Not documented in public sources for this exact serial range — verify with your dealer or the PC03-1 operation & maintenance manual | Komatsu genuine antifreeze/coolant (AF-NAC or equivalent long-life coolant), mixed per climate |
| Fuel tank | Not documented in public sources for this exact serial range — verify with your dealer or the PC03-1 operation & maintenance manual | Diesel fuel |
| Hydraulic system and tank | Not documented in public sources for this exact serial range — verify with your dealer or the PC03-1 operation & maintenance manual | Komatsu genuine hydraulic oil (HO), grade per ambient temperature |
| Final drives / travel reduction gear (each) | Not documented in public sources for this exact serial range — verify with your dealer or the PC03-1 operation & maintenance manual | Komatsu genuine gear oil (TO), grade per ambient temperature |
| Grease points | Spec only, no fill volume applies | Komatsu genuine multipurpose grease (G2-LI grade), per lubrication chart intervals |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Komatsu 1D84-1A(S/N 00101-UP) maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 50 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
| Every 4,000 h |
|
Servicing the 1D84-1A(S/N 00101-UP) beyond the schedule
Predictive Maintenance & Fluid Analysis
On an engine this small, oil sampling is less about long-term trending and more about catching contamination early. Pull a sample at every oil change and watch for fuel dilution, a sign the injection pump or the single injector is starting to leak, and for coolant intrusion. Track cold-start compression and exhaust smoke color at each service interval; on a one-cylinder engine, a drop in compression shows up in performance long before it would on a multi-cylinder block.
Corrective & Common Repairs
Most hard-start or rough-idle complaints on the 1D84-1A trace to the fuel side, since there is one injector, one injection pump, and one set of low-pressure lines to check. Verify the governor linkage and throttle cable are free and correctly adjusted before condemning the pump itself. Because the engine is naturally aspirated, a clogged air cleaner element restricts intake fast and robs power out of proportion to the engine's size — check it before chasing a fuel-system fault.
Overhaul & Rebuild Points
At overhaul, prioritize the cylinder liner, piston, and ring set, since the small bore sees a high relative duty cycle in a mini excavator's start-stop work. Check crankshaft end-play and main and rod bearing clearance while the engine is apart. Recondition or replace the injection pump and nozzle together rather than separately — on a single-cylinder engine, an out-of-spec injector affects every combustion event, not a fraction of them.
Seasonal & Environment Servicing
PC03-1 units doing this era's typical light landscaping and utility trenching work put plenty of dust through the intake, so clean or replace the air cleaner element more often in dry, dusty conditions. Drain condensation from the fuel tank before winter storage. On preserved or restored units, run the engine periodically under light load instead of letting it sit idle for long stretches — ring and injector seals dry out quickly on a single-cylinder diesel left unused.
1D84-1A(S/N 00101-UP) common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| YM114654-55600 | Fuel Filter Ass'Y | Fuel system service | Check fitment → |
| YM102103-55520 | O-Ring,(For Fuel Filter) | Fuel system service | Check fitment → |
| YM171051-92760 | Wrench,Fuel Filter? Water Separator | Fuel system service | Check fitment → |
| YM114250-35060 | Filter,Oil | Lubrication service | Check fitment → |
| YM114650-12590 | Element Ass'Y | Scheduled service item | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
1D84-1A(S/N 00101-UP) fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| Oil pressure warning lamp (red) | Engine oil pressure has dropped below the switch threshold | Low oil level, worn oil pump, clogged strainer, or wrong-viscosity oil | Stop engine immediately, check oil level and quality before restarting |
| Charge/alternator warning lamp (red) | Charging circuit not producing output at running speed | Loose or broken drive belt, faulty regulator, or wiring fault | Check belt tension and battery terminals, test charging output |
| Overheat lamp (if fitted, liquid-cooled variant only) | Cylinder head or coolant temperature above safe limit | Low coolant, blocked fins/radiator, fan belt failure | Idle down, shut off, let cool, inspect cooling airflow/coolant before restart |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
1D84-1A(S/N 00101-UP) attachments & work tools
Host machine and work-tool context
This engine (S/N 00101-UP) is the factory-fitted power unit on the Komatsu PC03-1, a micro/mini crawler excavator in the roughly 0.75 t class (built early-to-mid 1990s). Work-tool compatibility below is for that excavator chassis, not a standalone genset, pump, or industrial power-unit package. A later technical sheet for the same PC03-1 chassis lists the 1D84-1C engine, so this engine suffix appears to correspond to an earlier production run within the same model; do not carry 1D84-1B or 1D84-1C specific data onto the 1A.
Digging buckets
Direct pin-on digging buckets sized for this class, roughly 150 to 600 mm (6 to 24 in) wide, matched to the machine's standard bucket capacity of about 0.02 cubic meters. A wider grading or ditching bucket around 750 mm (30 in) is also listed for this model.
Bucket mounting / coupler system
Buckets mount on a simple two-pin direct connection; wear pins, bushings and seals are sold as a separate kit. No hydraulic quick-coupler is offered at this micro-excavator size, consistent with the class and era of this machine.
Hydraulic breaker fitment
Light-duty hydraulic breakers sized for sub-1-tonne excavators appear in general aftermarket lines for this machine class, but the base hydraulic pump output (roughly 20 L/min at about 155 to 160 bar, per class-level data) is on the low end for breaker duty. Breaker use is not documented as a standard factory arrangement for this model; confirm with a dealer before fitting.
Dozer/leveling blade
A front blade is commonly offered as factory-optional equipment on this micro-excavator class for backfilling and leveling. Exact blade width and lift/dig depth figures are not documented for this specific engine's serial range; treat as varies by configuration.
Auxiliary hydraulics for powered attachments
The base machine's single hydraulic circuit is dedicated to boom, arm and bucket functions; a separate auxiliary/aux-flow circuit is not documented as standard equipment. Any powered attachment (breaker, auger) would need an add-on plumbing kit rather than a factory-piped auxiliary line.
All 1D84-1A(S/N 00101-UP) assemblies by section
Every catalogued assembly group for the Komatsu 1D84-1A(S/N 00101-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Cooling System
Komatsu : 1d84-1a(S/N 00101-Up) : Cooling System : Flywheel And Cooling Fan Case
| YM***01 | Case,Fan | 1 |
| YM***00 | Cushion | 4 |
| YM***92 | Flywheel Ass'Y | 1 |
Cylinder Block
Komatsu : 1d84-1a(S/N 00101-Up) : Cylinder Block : Balancer Shaft(#00101-20100)
| YM***10 | Balancer Ass'Y | 1 |
| YM***34 | Bearing,Ball | 2 |
Komatsu : 1d84-1a(S/N 00101-Up) : Cylinder Block : Camshaft And Tappet(#00101-20100)
| YM***81 | Camshaft Ass'Y | 1 |
| YM***01 | Rod,Push | 2 |
| YM***60 | Tappet | 1 |
Komatsu : 1d84-1a(S/N 00101-Up) : Cylinder Block : Crankshaft(#00101-20100)
| YM***02 | Bolt Plated | 1 |
| YM***40 | Key | 1 |
| YM***00 | Crankshaft Ass'Y | 1 |
Komatsu : 1d84-1a(S/N 00101-Up) : Cylinder Block : Cylinder Block(#00101-20100)
| YM***40 | Cap Ass'Y,Oil Gauge | 1 |
| YM***20 | Seal | 1 |
| YM***08 | Seal,Oil | 1 |
Komatsu : 1d84-1a(S/N 00101-Up) : Cylinder Block : Front Cover
| YM***40 | Cap Ass'Y,Oil Gauge | 1 |
| YM***51 | Sensor,Oil Pressure | 1 |
| YM***08 | Seal,Oil | 1 |
Komatsu : 1d84-1a(S/N 00101-Up) : Cylinder Block : Piston And Connecting Rod
| YM***42 | Piston Ring Ass'Y | 1 |
| YM***23 | Piston Ass'Y | 1 |
| YM***02 | Piston Ring Ass'Y | 1 |
Cylinder Head
Komatsu : 1d84-1a(S/N 00101-Up) : Cylinder Head : Air Cleaner And Mounting
| YM***50 | Sponge | 1 |
| YM***50 | Nut | 1 |
| YM***60 | Washer,Seal | 1 |
Komatsu : 1d84-1a(S/N 00101-Up) : Cylinder Head : Air Intake Manifold And Connection
| YM***02 | Screw | 2 |
| YM***52 | Stud | 2 |
| YM***02 | Nut | 2 |
Komatsu : 1d84-1a(S/N 00101-Up) : Cylinder Head : Cylinder Head
| YM***40 | Bolt | 2 |
| YM***00 | Valve,Intake | 1 |
| YM***80 | Retainer, Spring | 2 |
Komatsu : 1d84-1a(S/N 00101-Up) : Cylinder Head : Cylinder Head Cover
| YM***40 | Spring | 1 |
| YM***02 | Screw | 2 |
| YM***01 | Shaft | 1 |
Komatsu : 1d84-1a(S/N 00101-Up) : Cylinder Head : Muffler And Mounting
| YM***00 | Gasket (Kit) | 1 |
| YM***00 | Muffler | 1 |
| YM***62 | Bolt,(For Shipping) | 6 |
Komatsu : 1d84-1a(S/N 00101-Up) : Cylinder Head : Rocker Arm
| YM***62 | Arm | 1 |
| YM***52 | Arm | 1 |
| YM***61 | Support,Rocker Arm | 1 |
Electrical System
Komatsu : 1d84-1a(S/N 00101-Up) : Electrical System : Dynamo And Mounting(#00101-20100)
| YM***10 | Bracket | 1 |
| YM***90 | Dynamo Ass'Y | 1 |
| YM***42 | Screw | 3 |
Komatsu : 1d84-1a(S/N 00101-Up) : Electrical System : Starting Motor
| YM***67 | Bolt | 2 |
| YM***10 | Starting Motor Ass'Y | 1 |
| YM***13 | Brush (-) | 1 |
Komatsu : 1d84-1a(S/N 00101-Up) : Electrical System : Starting Motor And Mounting
| YM***02 | Screw | 2 |
| (Y***0) | Starting Motor Ass'Y,(See Fig.0661) | 1 |
Fuel System
Komatsu : 1d84-1a(S/N 00101-Up) : Fuel System : Fuel Feed Pump
| YM***00 | Feed Pump Ass'Y | 1 |
Komatsu : 1d84-1a(S/N 00101-Up) : Fuel System : Fuel Filter
| YM***00 | Gasket | 2 |
| YM***00 | O-Ring (Kit) | 1 |
| YM***50 | Plug,Air | 2 |
Komatsu : 1d84-1a(S/N 00101-Up) : Fuel System : Fuel Injection Pump
| YM***20 | Packing | 1 |
| YM***50 | Seat | 1 |
| YM***08 | Pin,Spring | 1 |
Komatsu : 1d84-1a(S/N 00101-Up) : Fuel System : Fuel Injection Pump And Piping
| YM***30 | Cover | 1 |
| YM***50 | Pipe | 1 |
| YM***02 | Nut | 3 |
Komatsu : 1d84-1a(S/N 00101-Up) : Fuel System : Fuel Nozzle And Spill Pipe
| YM***90 | Pipe | 1 |
| YM***00 | Holder Ass'Y | 1 |
| YM***20 | Spring | 1 |
Komatsu : 1d84-1a(S/N 00101-Up) : Fuel System : Governor Control(#00101-20100)
| YM***00 | Governor Lever Ass'Y | 1 |
| YM***52 | Spring,Return | 1 |
| YM***60 | Handle,Regulator | 1 |
Lubricating Oil System
Komatsu : 1d84-1a(S/N 00101-Up) : Lubricating Oil System : Lubricating Oil Filter
| YM***24 | O-Ring (Kit) | 1 |
| YM***22 | Screw | 2 |
| YM***60 | Filter,Oil | 1 |
Komatsu : 1d84-1a(S/N 00101-Up) : Lubricating Oil System : Lubricating Oil Pump
| YM***70 | Cover | 1 |
| YM***70 | O-Ring (Kit) | 1 |
| YM***42 | Bolt | 3 |
Tool And Kit
Komatsu : 1d84-1a(S/N 00101-Up) : Tool And Kit : Gasket Kit
| YM***00 | Gasket (Kit) | 1 |
| YM***40 | Seal,Valve Stem (Kit) | 2 |
| YM***80 | O-Ring (Kit) | 1 |
Komatsu : 1d84-1a(S/N 00101-Up) : Tool And Kit : Tool
| YM***60 | Wrench,Fuel Filter? Water Separator | 1 |
| YM***21 | Puller,Flywheel | 1 |
| YM***54 | Bolt | 3 |
Frequently asked questions
What engine powers the Komatsu 1D84-1A (S/N 00101-UP)?
It is Komatsu's own single-cylinder, direct-injection diesel of about 0.39 liter (23.7 cu in) displacement, rated at 5.5 kW (7.4 hp) at 2800 rpm. The same rated output is published for the later 1D84-1B and 1D84-1C running changes and for the 1D84 engine carried into the PC03-2 excavator.
What is the operating weight of the machine this engine powers?
The Komatsu PC03-1 micro excavator that used this engine weighed about 0.75 t (roughly 1,650 lb) as originally built. The successor PC03-2, which kept the same 1D84 engine family, weighed about 0.82 to 0.87 t (1,800 to 1,920 lb). Dry weight of the engine itself is not documented for this serial range.
What replaced the 1D84-1A engine?
Komatsu kept the 1D84 engine through the PC03-2 generation (1997-98) before switching to a two-cylinder 2D68E-3A engine on the PC03-2F (1999-2002), ending the single-cylinder engine line in this micro-excavator family.
What 1D84-1A(S/N 00101-UP) owners discuss
What's it like to start and run this engine day to day, according to owners of this micro-excavator platform?
What undercarriage wear pattern shows up on this size of Komatsu mini excavator?
Does the hydraulic system need special attention on this class of Komatsu excavator?
What do mechanics check first on a no-start or electrical complaint on this engine family?
Why do owners say aftermarket parts are hit-or-miss on this machine?
Do the 1D84-1A, -1B, and -1C suffixes mean different engines?
What should a buyer check before purchasing a used 1D84-1A(S/N 00101-UP)-powered excavator?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
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