Komatsuhydraulic excavatormedium (pc100 - pc270)

Komatsu S4D105-5B(S/N 100028-UP)

Maintenance schedule, common problems & OEM parts breakdown

Search live S4D105-5B(S/N 100028-UP) parts

The Komatsu S4D105-5B is a mid-size crawler hydraulic excavator powered by the S4D105-5 turbocharged diesel engine. It belongs to the PC120 class with an operating weight of approximately 25,350 lb (11,500 kg). Production years for this series span the late 1990s through the early 2000s. The machine succeeded the PC120-1 and was followed by the PC120-2 and PC120-3 generations. Configurations offered include standard and long boom/stick options, varying track shoe widths, and regional emissions packages.

Across the S4D105-5B generation, Komatsu refined hydraulic flow and engine efficiency to meet evolving productivity demands. The S4D105-5 engine provides 90 hp gross power with a displacement of 264.3 cu in (4.3 L). This machine remains significant in the used and parts market due to its widespread deployment in utility and light construction work. The S4D105-5 engine is a common platform across multiple Komatsu models, ensuring high parts availability and a robust aftermarket support network for rebuild kits and undercarriage components.

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 S4D105-5B(S/N 100028-UP) specifications

Engine

Model	S4D105-5
Gross Power	90 hp
Aspiration	Turbocharged
Displacement	264.3 cu in (4.33 L)

Weights

Operating Weight	25,350 lb (11,499 kg)
Ground Pressure	5.97 psi (41.2 kPa)

Dimensions

Transport Length	24.51 ft (7.47 m)
Transport Width	7.98 ft (2.43 m)
Transport Height	8.78 ft (2.68 m)
Tail Swing Radius	7.3 ft (2.23 m)
Track Shoe Width	18.9 in (480 mm)
Ground Clearance	1.32 ft (0.40 m)
Undercarriage Length (Track on Ground)	8.44 ft (2.57 m)
Track Gauge	6.4 ft (1.95 m)

Performance

Max Digging Depth	16.41 ft (5.00 m)
Max Reach at Ground	24.74 ft (7.54 m)
Max Dump Height	17.13 ft (5.22 m)
Max Cutting Height	24.78 ft (7.55 m)
Swing Speed	12 rpm
Max Travel Speed	2.24 mph (3.60 km/h)

Forces

Bucket Digging Force	Not documented for this exact serial range — verify with your dealer
Stick/Arm Digging Force	Not documented for this exact serial range — verify with your dealer

Service Capacities (Summary)

Fuel Tank Capacity	60.8 gal (230 L)
Hydraulic System Fluid Capacity	38.4 gal (145 L)
Hydraulic System Relief Valve Pressure	2,500 psi (17.2 MPa)
Hydraulic Pump Flow Capacity	85.4 gal/min (323 L/min)
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

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

S4D105-5B(S/N 100028-UP) fluids & capacities

System	Capacity	Recommended fluid
Engine crankcase (with filter)	13 L (3.4 US gal)	Komatsu Diesel Engine Oil (SAE 10W or 15W-40, API CD or later); varies by climate/temperature per factory spec sheet
Cooling system	22 L (5.8 US gal)	Komatsu Super-coolant AF-NAC (JIS K 2234-1987 / ASTM 3306 compliant); varies by machine series per factory spec sheet
Fuel tank	230 L (60.8 US gal)	ASTM D975 No.1 and No.2 diesel fuel per factory spec sheet
Hydraulic system total	145 L (38.4 US gal)	Komatsu Hydraulic Oil HO (ISO VG46, DIN 51524 Part 2, class HLP); varies by climate/temperature per factory spec sheet
Hydraulic tank	Not documented for this exact serial range — verify with your dealer	Not documented for this exact serial range — verify with your dealer
Final drive (each)	Not documented for this exact serial range — verify with your dealer	Not documented for this exact serial range — verify with your dealer
Swing drive	Not documented for this exact serial range — verify with your dealer	Not documented for this exact serial range — verify with your dealer
Pilot/other circuits	Not documented for this exact serial range — verify with your dealer	Not documented for this exact serial range — verify with your dealer
Grease	Not applicable	Not applicable

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

Komatsu S4D105-5B(S/N 100028-UP) maintenance schedule

Service interval	Tasks
Every 10 h	Check engine oil level and condition. Check hydraulic fluid level at the sight glass. Check coolant level and ensure the cap is secure. Check fuel level and drain water from the separator. Check DEF level on Tier 4 machines. Check air filter restriction indicator. Inspect track tension and shoe/pad condition. Inspect hydraulic hoses for cracks or leaks. Inspect pins, bushings, and attachment points. Clear debris from radiator and oil cooler fins. Check for fluid leaks under the machine. Verify ROPS/FOPS integrity and seat belt function. Test horn, backup alarm, and lights. Verify emergency shutoff accessibility. Start engine and check gauges and KOMTRAX display. Test all controls for smooth response. Test service and parking brakes.
Every 250 h	Change engine oil and filter. Grease all points on the boom, stick, bucket, and swing bearing. Check fluid levels. Check the air filter outer element. Inspect belts, hoses, and clamps. Perform a visual walk-around inspection.
Every 500 h	Replace the fuel filter. Replace the hydraulic return filter. Perform battery service and load test. Test the coolant SCA. Collect a KOWA oil sample. Perform a detailed undercarriage inspection. Check the final drive oil level. Check the swing machinery oil level.
Every 1,000 h	Collect a hydraulic oil sample. Change the final drive oil on both sides. Inspect the turbocharger. Take wear measurements. Check the valve adjustment. Perform a structural inspection of the boom and stick. Clean or replace the air filter outer element. Inspect and replace worn belts and hoses. Load test the battery and alternator.
Every 2,000 h	Change the hydraulic system oil. Flush and replace the coolant. Perform a comprehensive component evaluation. Change the swing machinery oil. Perform a comprehensive structural inspection. Check and torque ROPS bolts. Check and torque cutting edge and end bit bolts. Inspect and replace worn undercarriage components.

Servicing the S4D105-5B(S/N 100028-UP) beyond the schedule

Predictive Maintenance & Fluid Analysis

Utilize the KOWA Komatsu Oil Wear Analysis program at every 500-hour interval to monitor engine oil, hydraulic fluid, and coolant health. Check hydraulic fluid for particle count, ISO cleanliness, and water content. Monitor engine oil for wear metals like iron, copper, and lead, as well as contaminants such as silicon and sodium. Test coolant pH, SCA concentration, and glycol content. Review KOMTRAX telematics data for load frequency and fault codes to anticipate component failures before they occur.

Corrective & Common Repairs

Address intermittent starting or random shutdowns by inspecting the Electronic Control Module (ECM) wiring and power supply. Replace worn fuel delivery components if power loss or increased fuel usage occurs. Fix hydraulic slow movements by checking the LS-EPC solenoid valve and main pump pressure. Inspect the turbocharger for boost leaks or bearing play. Replace cracked hydraulic hoses and worn pins and bushings on the boom, stick, and bucket to maintain structural integrity and hydraulic efficiency.

Overhaul & Rebuild Points

Plan the S4D105-5 engine inframe overhaul between 10,000 and 15,000 hours. The overhaul kit includes cylinder liners, pistons, piston pins, rod bushings, main and connecting rod bearings, thrust bearings, intake and exhaust valves, valve seats, and valve guides. Inspect the hydraulic pump and swing motor for wear. Replace final drive oil and inspect gears for pitting. Evaluate the undercarriage for track stretch, roller wear, and sprocket tooth profile loss.

Seasonal & Environment Servicing

In cold climates, use Komatsu Super Coolant AF-NAC and ensure the battery is fully charged to prevent starting issues. Drain water from the fuel separator daily to prevent ice formation. In dusty environments, check the air filter restriction indicator frequently and clean or replace the outer element as needed. Clear debris from the radiator and oil cooler fins to prevent overheating. Inspect hydraulic hoses for brittleness caused by UV exposure and extreme temperatures. Grease all pivot points more frequently in wet or muddy conditions.

S4D105-5B(S/N 100028-UP) common service parts

Part number	Part	Notes
07281-00197	Clamp,(With Pre-Fuel Filter)	Fuel system service	Check fitment →
600-311-6220	Cartridge,Fuel Filter	Fuel system service	Check fitment →
6134-71-6100	Fuel Filter Ass'Y	Fuel system service	Check fitment →
6127-61-2971	O-Ring,Oil Cooler Element	Lubrication service	Check fitment →
6136-61-2190	O-Ring,Oil Cooler Element	Lubrication service	Check fitment →

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S4D105-5B(S/N 100028-UP) fault codes & troubleshooting

Code	Meaning	Likely cause	What to do
CA115	Engine crankshaft speed sensor failure	Faulty sensor, broken wiring, or corroded connector at the pin interface.	Replace the speed sensor and verify voltage at the pin connector.
CA111	Internal engine controller fault	Malfunction within the Electronic Control Module (ECM).	Replace or reprogram the ECM.
CA451	Common rail pressure sensor feedback value too high	Malfunction in the rail pressure sensor or an actual overpressure condition in the fuel system.	Diagnose the fuel rail pressure sensor and check pump lines.
CA122	Intake air pressure sensor feedback voltage too high	Faulty intake pressure sensor or wiring issue.	Verify the intake pressure sensor and wiring integrity.
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	Faulty Intake Air Temperature (IAT) sensor.	Replace or test the IAT sensor.
CA154	Intake air temperature sensor feedback voltage too low	Faulty Intake Air Temperature (IAT) sensor.	Replace or test the IAT sensor.
CA441	Battery voltage too low	Weak battery or failing alternator.	Replace the alternator or battery; check the voltage regulator.
CA442	Battery voltage too high	Failing alternator or voltage regulator.	Replace the alternator or battery; check the voltage regulator.
DGH2KB	Hydraulic oil temperature sensor short circuit	Shorted hydraulic oil temperature sensor.	Replace the temperature sensor.

Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.

S4D105-5B(S/N 100028-UP) attachments & work tools

Buckets

The machine belongs to the 10-ton class (PC100/PC120 series). Standard general duty bucket capacity ranges from 0.5 to 0.7 cubic meters (0.65 to 0.91 cubic yards). Heavy duty and rock buckets typically range from 0.4 to 0.6 cubic meters (0.52 to 0.78 cubic yards). Pin-on mounting is standard for this generation; quick coupler compatibility varies by configuration and series.

Hydraulic hammers

Komatsu manufactures its own line of hydraulic breakers, including the JMHB-H and JMHB-V series. The JMHB-H class operates between 804.7 and 7,189.3 lbs (365 and 3,261 kg), while the JMHB-V class ranges from 3,197 to 7,561.9 lbs (1,449 to 3,430 kg). These sizes match the 10-ton excavator class.

Quick couplers

Lehnhoff couplers are listed as compatible with the Komatsu range, covering excavators from PC09 to PC1250. Both mechanical and hydraulic quick coupler types are available for this size class.

Thumbs/grapples

Aftermarket suppliers such as Strickland MFG and Rhinox Group offer mechanical pin grab couplers and land clearance rakes for Komatsu excavators. Specific thumb kit dimensions or hydraulic flow requirements are not documented for this exact serial range in the provided sources.

Rippers

Ripper specifications are not documented for this exact serial range in the provided sources.

Hydraulic-kit notes

Komatsu specifies Komatsu Genuine Lubricants for hydraulic systems. Recommended fluids include HO56 hydraulic oil and TO10 or TO30 powertrain oil. The machine operates at a system pressure of 2500 psi (17.2 MPa) with a flow rate of 85.4 gal/min (323.5 L/min).

All S4D105-5B(S/N 100028-UP) assemblies by section

Every catalogued assembly group for the Komatsu S4D105-5B(S/N 100028-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Cooling And Electrical Systems

Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Alternator And Mounting

01***60	Bolt,(Without Alternator Bracket)	2
01***25	Bolt,(Sandy? Dusty Terrain Spec.)	1
01***30	Bolt,(For France Noise Suppression)	2
01***50	Bolt	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Alternator(#100028-153564)

60***51	Alternator A. (25a)	1
KD***52	Bolt,Through	3
KD***70	Rear Bracket Ass'Y	1
KD***70	Retainer	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Alternator(#153565-163823)

60***40	Alternator A. (25a),(See Fig.0641)	1
KD***52	Bolt,Through	3
KD***70	Rear Bracket Ass'Y	1
KD***70	Retainer	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Alternator(#163824-)

60***30	Alternator A. (25a),(With Non Hardening Pulley)	1
KD***57	Bearing,Ball? Front	1
KD***70	Bracket,Front	1
KD***90	Nut	2

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Corrosion Resistor (Except Japan)

01***25	Bolt,(Sandy? Dusty Terrain Spec.)	4
01***29	Washer,Spring (Cold Weather Spec.)	4
01***30	Washer,Spring(Sandy?Dusty Terrain S.)	4
02***32	Bolt,(With Joy Stick Steering)	4

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Heater Signal And Relay Switch

60***70	Switch,Air Intake Heater	1
60***60	Switch,Heater Relay	1
60***71	Signal,Signal	1
61***10	Cap	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Starting Motor (1/2) (7.5kw) (Except Japan)

60***81	Starting Motor Ass'Y,7.5kw	1
KD***01	O-Ring	1
KD***70	Center Bracket A	1
KD***90	Field Coil Ass'Y	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Starting Motor (1/2)(#102089-163823)

60***43	Starting Motor A.,(5.5kw) (See Fig.0661)	1
KD***10	Clutch Ass'Y,Over Running	1
KD***01	O-Ring	1
KD***60	Metal,Center	2

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Starting Motor (1/2)(#163824-)

60***80	Starting Motor Ass'Y,(5.5kw)	1
KD***30	Bracket,Center	1
KD***50	O-Ring	1
KD***10	Screw	4

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Starting Motor (2/2) (7.5kw) (Except Japan)

KD***01	Washer,Seal	2
KD***30	Holder	1
KD***05	Terminal Ass'Y	1
KD***01	Washer,(Not Shown)	2

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Starting Motor (2/2)(#102089-163823)

KD***01	Washer,Seal	2
KD***80	Shift Lever Ass'Y	1
KD***30	Contactor,Moving	1
KD***30	Holder	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Starting Motor (2/2)(#163824-)

KD***50	O-Ring	1
KD***30	Cap, Gum	1
KD***10	Ring,Clip	2
KD***10	Magnetic Switch A	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Starting Motor And Mounting

01***35	Bolt - Torque Converter Totransmission Mounting	3
01***36	Washer,Radio Controlled Slag Handling	3
07***00	O-Ring,(F4350-65a1 -5 )	1
08***19	Cap, At Heater Relay Terminals	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Starting Motor(#100028-102088)

60***42	Starting Motor A.,(5.5kw) (See Fig.2546)	1
KD***10	Clutch Ass'Y,Over Running	1
KD***80	Shift Lever Ass'Y	1
KD***60	Metal,Center	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Water Pump And Cooling Fan(#100028-149999)

01***18	Bolt	2
01***20	Bolt,(Sandy? Dusty Terrain Spec.)	2
01***30	Bolt,(Cold Terrain Spec.)	3
01***22	Bolt	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cooling And Electrical Systems : Water Pump And Cooling Fan(#150007-)

01***30	Bolt,(Cold Terrain Spec.)	3
01***50	Bolt	6
01***55	Bolt,(For Suction? Reversible Fan)	2
01***60	Bolt (M10-1.50x60)	2

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Cylinder Block

Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Block : Camshaft And Tappet

01***25	Bolt,(Without Auto Priming System)	2
01***25	Washer,Spring?(Sandy And Dusty Spec.)	2
01***16	Washer,(For Shipping)	2
01***16	Washer,(For 35a Alternator)	2

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Block : Crankshaft

61***11	Bolt,Nylock (K2)	1
61***00	Metal Ass'Y	1
61***50	Thrust Metal Ass'Y	1
61***00	Metal Ass'Y	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Block : Cylinder Block

01***20	Bolt	2
01***20	Bolt,(Sandy? Dusty Terrain Spec.)	1
01***25	Bolt,(Sandy? Dusty Terrain Spec.)	4
01***30	Bolt,(For France Noise Suppression)	4

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Block : Cylinder Block(#100028-149999)

01***20	Bolt	2
01***20	Bolt,(Sandy? Dusty Terrain Spec.)	1
01***25	Bolt,(Sandy? Dusty Terrain Spec.)	4
01***30	Bolt,(For France Noise Suppression)	12

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Block : Engine Support

01***45	Bolt,(For Power Tilt Mech Angle)	8
01***55	Bolt, Mount Lh Bracket	8
20***20	Bracket,Rear	2
20***30	Bracket,Front? L.H	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Block : Flywheel And Flywheel Housing

01***40	Bolt,(Dust And Dirt Protection)	9
01***60	Bolt, Trunnion Cap	2
01***55	Bolt	6
01***36	Washer,Radio Controlled Slag Handling	11

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Block : Front Cover

01***20	Bolt,(Sandy? Dusty Terrain Spec.)	6
01***22	Bolt,(Cold Terrain Spec.)	4
01***25	Bolt,(Without Auto Priming System)	5
01***30	Bolt,(Cold Terrain Spec.)	7

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Block : Oil Pan

01***22	Bolt,(Cold Terrain Spec.)	20
01***25	Bolt,(Without Auto Priming System)	8
01***30	Bolt,(Cold Terrain Spec.)	2
01***25	Washer,Spring?(Sandy And Dusty Spec.)	30

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Block : Piston And Connecting Rod

04***18	Ring, Retaining	2
61***40	Crank Pin Metal A	4
61***00	Connecting Rod Ass'Y	4
61***30	Bushing	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Block : Power Take Off

01***30	Bolt,(For France Noise Suppression)	12
01***55	Bolt, Mount Tube To Switch Pump	12
01***30	Washer,Spring(Sandy?Dusty Terrain S.)	12
01***32	Washer,(With Auto Emergency Steering)	12

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Cylinder Head

Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Head : Air Cleaner

01***25	Bolt - Rear Guard Mounting	8
01***06	Nut, Regular Hexagon (M8-1.25)	6
01***25	Washer,Spring?(Sandy And Dusty Spec.)	6
01***36	Washer,Radio Controlled Slag Handling	8

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Head : Air Intake Manifold And Connection

01***65	Bolt,(For Alternator Bracket Mount)	6
01***75	Bolt,(See Fig.0142)	4
01***80	Bolt,(See Fig.0131)	1
01***20	Bolt,(Large Capacity Type) (Std)	2

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Head : Cylinder Head

01***25	Bolt,(Sandy? Dusty Terrain Spec.)	1
01***30	Bolt,(For France Noise Suppression)	1
01***30	Washer,Spring(Sandy?Dusty Terrain S.)	2
01***16	Washer,(With Shoe Slip Control)	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Head : Cylinder Head Cover

01***16	Bolt,(For Slag Handling)	1
01***25	Washer,Spring?(Sandy And Dusty Spec.)	1
07***23	Clamp - Hose	1
07***89	Clamp,(For Japan)	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Head : Exhaust Manifold And Turbocharger

01***60	Bolt (M10-1.50x60)	2
01***80	Bolt, Mount Strainer Flange	6
01***60	Screw	2
01***80	Bolt	6

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Head : Muffler

01***30	Bolt,(For France Noise Suppression)	4
01***70	Bolt, Spacer	3
01***32	Washer,(With Auto Emergency Steering)	3
07***32	Hose,(See Fig.0411-11)	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Head : Rocker Arm

01***80	Bolt,(Shim 5 Pieces Over)	1
01***06	Nut, Regular Hexagon (M8-1.25)	8
01***36	Washer,Radio Controlled Slag Handling	4
61***00	Rocker Arm Ass'Y	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Cylinder Head : Turbocharger (Except Japan)

61***00	Turbocharger Ass'Y,(See Fig.2141)	1
61***01	Turbocharger Ass'Y,(See Fig.2141)	1
61***02	Turbocharger Ass'Y	1
61***00	Turbocharger Ass'Y	1

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Fuel System

Komatsu : S4d105-5b(S/N 100028-Up) : Fuel System : Fuel Filter

01***16	Bolt (Welded)	2
01***20	Bolt	2
01***35	Bolt, Mounting - Flywheel Housing End	2
01***50	Bolt	2

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Komatsu : S4d105-5b(S/N 100028-Up) : Fuel System : Fuel Injection Pump (Feed Pump)

DK***20	Bolt, Joint	1
DK***20	Pump,Priming	1
DK***00	Spring,Piston	1
DK***00	Adapter	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Fuel System : Fuel Injection Pump (Governor) (1/2)

DK***40	Gasket,Air Compressor	2
DK***00	Collar	1
DK***00	Nut,Cap	1
DK***20	Cover	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Fuel System : Fuel Injection Pump (Governor) (2/2)

DK***00	Adapter	1
DK***00	Spring	1
DK***00	Nut,Lock	1
DK***10	Pin,Spring	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Fuel System : Fuel Injection Pump (Pump)

61***00	Injection Pump Ass'Y	1
61***00	Injection Pump Ass'Y	1
DK***20	Plunger Ass'Y	4
DK***20	Cover	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Fuel System : Fuel Injection Pump And Piping

01***20	Bolt	3
01***30	Bolt	1
01***35	Bolt	1
01***30	Bolt,(Cold Weather Spec.)	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Fuel System : Fuel Injection Pump And Piping(#100028-103414)

01***30	Bolt,(Cold Weather Spec.)	1
01***55	Bolt	1
01***70	Bolt	3
01***35	Stud	3

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Komatsu : S4d105-5b(S/N 100028-Up) : Fuel System : Nozzle Holder

01***55	Bolt,(For Trimming Dozer)	8
01***25	Washer,Spring?(Sandy And Dusty Spec.)	8
07***12	Gasket,Mechanical Pump Piping	2
61***52	Bolt, Joint	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Fuel System : Water Separator

07***60	O-Ring,(For Pc750?800?1800) (A2610)	1
60***00	Water Separator A.,(4d105-5h? 4d105-5t)	1
60***60	Plug,Drain (4d105-5h? 4d105-5t)	1
60***00	Water Separator A.,(See Fig.2415)	1

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Lubricating Oil System

Komatsu : S4d105-5b(S/N 100028-Up) : Lubricating Oil System : Lubricating Oil Cooler

01***25	Bolt,(Without Auto Priming System)	5
01***30	Bolt,(Cold Terrain Spec.)	3
01***35	Bolt,(Without Auto Priming System)	9
01***40	Bolt,(For Position Fixing)	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Lubricating Oil System : Lubricating Oil Filter

01***90	Bolt	1
01***35	Bolt, Mounting - Flywheel Housing End	1
01***25	Bolt (M10x1.50x25)	1
01***25	Washer,Spring?(Sandy And Dusty Spec.)	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Lubricating Oil System : Lubricating Oil Pump And Suction Pipe(#100028-149999)

01***25	Bolt,(Without Auto Priming System)	1
01***30	Bolt,(Cold Terrain Spec.)	2
01***50	Bolt,(For Trimming Dozer)	4
01***25	Bolt,(Sandy? Dusty Terrain Spec.)	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Lubricating Oil System : Lubricating Oil Pump And Suction Pipe(#150007-)

01***25	Bolt,(Without Auto Priming System)	1
01***30	Bolt,(Cold Terrain Spec.)	3
01***40	Bolt,(For Position Fixing)	1
01***45	Bolt,(S6d155-4b)	1

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Komatsu : S4d105-5b(S/N 100028-Up) : Lubricating Oil System : Turbocharger Lubricating Oil Piping

01***22	Bolt,(Cold Terrain Spec.)	2
01***35	Bolt, Mounting - Flywheel Housing End	2
01***25	Washer,Spring?(Sandy And Dusty Spec.)	2
01***30	Washer,Spring(Sandy?Dusty Terrain S.)	2

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Tool And Kit

Komatsu : S4d105-5b(S/N 100028-Up) : Tool And Kit : Gasket Kit

01***16	Washer,Lock? Injection Gear	1
07***65	O-Ring,Injection Pump Case	1
07***00	O-Ring,(F4350-65a1 -5 )	1
07***22	O-Ring,(See Fig.Y1852-01a0)	1

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S4D105-5B(S/N 100028-UP) serial number reference

The engine serial number plate is located on the left side of the engine block or on a metal plate affixed near the valve cover. The prefix is the alphanumeric engine model code (e.g., S4D105-5B) stamped on this plate, distinct from the machine's chassis serial number.

Prefix	Identifies	Notes
S4D105-5B	Engine Model	Engine model S4D105-5B. Serial range 100028-149999. Fits Komatsu PC100-2 (S/N 13001-18000), PC120-2 (S/N 14001-Up), and PC100-3 (S/N 18001-Up). Note: PC100-2 units with serial numbers 150001 and above use engine S4D105-5B (S/N 150001-Up), distinct from the 100028-149999 range.

Frequently asked questions

What engine does the Komatsu S4D105-5B use?

The Komatsu S4D105-5B uses the S4D105-5 turbocharged diesel engine. It produces 90 hp gross power and has a displacement of 264.3 cu in (4.3 L).

What is the operating weight of the Komatsu S4D105-5B?

The operating weight of the Komatsu S4D105-5B is approximately 25,350 lb (11,500 kg). This varies by configuration, including boom/stick options and track shoe width.

What model replaced the Komatsu S4D105-5B?

The S4D105-5B engine was used in the PC120-2 and PC120-3 excavators. The PC120-3 is the direct successor in the PC120 series lineage for this engine platform.

What S4D105-5B(S/N 100028-UP) owners discuss

What engine powers the Komatsu S4D105-5B hydraulic excavator, and how does its configuration differ from the S4D102 series?

The S4D105-5B is a 4-cylinder, turbocharged diesel engine with a displacement of 264.3 cubic inches (4.33 liters). It is distinct from the S4D102 series, which is a different engine family. The S4D105-5B is typically paired with the PC100-2 and PC120-2 excavator models. The S4D102 variants are not applicable to this serial range and represent a separate powertrain configuration with different bore and stroke dimensions.

What are the known hydraulic behaviors and common failure patterns for this machine type?

Operators report that hydraulic performance degrades noticeably when the oil warms up due to internal leakage in the main pump or control valve. A common diagnostic pattern is weak performance in cold conditions that improves slightly as viscosity drops, or conversely, significant weakness only when hot. If all functions (boom, arm, bucket, swing, travel) become slow simultaneously, the issue is likely the main hydraulic pump, engine RPM, or hydraulic oil condition, not individual cylinders. If only one function is slow, check the specific cylinder seals, control valve spool, or load-holding valve.

What undercarriage and wear patterns are typical for the PC100/PC120 series equipped with this engine?

The PC100-2 and PC120-2 models utilize a Kato HD450VII swing motor and a Sumitomo SH100-2 travel motor. Undercarriage wear is accelerated by mud or debris packed into the track frames, which increases mechanical resistance. Track tension must be verified regularly, as repeated loosening is a common issue. Worn bushings and bearings in the track chain lead to noise, vibration, and premature track failure. The line is known for high resale value depreciation if major components like the pump or engine are allowed to fail, indicating that wear often correlates across major systems.

What are the engine quirks and maintenance requirements for the 4D105-5/S4D105-5 series?

The S4D105-5B engine (Serial Number 100028-the OEM part reference) requires specific attention to the fuel system. Air entering the fuel supply or clogged fuel filters can cause power loss under load. The engine relies on a feed pump driven by the injection pump cam. Coolant capacity is approximately 22 liters (varies by machine series) and engine oil capacity is approximately 13 liters (varies by machine series). Overheating during heavy excavation often indicates material packed between the radiator, hydraulic oil cooler, and charge-air cooler. The engine does not use replaceable cylinder liners in the same manner as older 95-series engines; sleeve removal requires specific rebuild kits.

What are the common electrical and sensor issues reported by owners?

Komatsu excavators rely heavily on electronic control systems. Common issues include intermittent starting, dashboard display failures, and random machine shutdowns. These are often triggered by a single faulty sensor or an unstable power supply. Multiple fault codes appearing simultaneously usually point to battery state of charge, poor engine/chassis grounds, or corroded connectors. A battery may show acceptable voltage at rest but collapse under the load of the starter, requiring a load test rather than a simple voltage check.

What specific items must be checked when buying a used Komatsu S4D105-5B (S/N 100028-UP)?

Verify the engine serial number falls within the 100028-the OEM part reference range for the S4D105-5B inframe overhaul kit applicability. Check the hydraulic oil condition and temperature behavior; weak performance when hot indicates internal pump or valve leakage. Inspect the undercarriage for packed debris and track tension. Verify the swing brake holds position and does not drift. Check for exhaust in the cooling system, which indicates failed cylinder sleeves or head gasket issues. Ensure the fuel tank vent is clear to prevent power loss. Confirm the exact serial prefix matches the PC100-2 or PC120-2 model specifications, as later models (PC100-3/PC120-3) may use different engines like the 6D95L-1A.

What safety-critical fixes require dealer verification?

Swing brake failure that allows the upper structure to drift or rotate uncontrollably. Engine overheating that leads to coolant expulsion or system pressurization. Hydraulic system leaks that create fire hazards or loss of control. Any repair involving the fuel injection pump timing or governor settings. Have your dealer verify these conditions using OEM service manuals and pressure testing equipment.

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

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