Komatsu S4D105-2B(S/N 18273-UP)
Maintenance schedule, common problems & OEM parts breakdown
The Komatsu S4D105-2B is a four-cylinder, turbocharged diesel engine belonging to the 105 Series, specifically covering serial numbers 18273 and up. It powers the D40A-1 and PL-1 crawler dozer lines, which are mid-size earthmoving machines with operating weights typically ranging from 15,000 to 20,000 lbs. Production of this specific engine configuration spans the late 1980s through the early 2000s. The S4D105-2B succeeded the S4D105-1 series and was eventually replaced by the S4D105-3 series (starting at serial 44579). Configurations offered include standard industrial and construction variants, often equipped with a Type T04B turbocharger and specific fuel system arrangements for the D40A-1 dozer chassis.
Across the 105 Series generations, primary changes involved emissions compliance updates, fuel system refinements, and turbocharger specifications. The S4D105-2B is significant in the used and parts market because it is a robust, mechanically controlled engine widely used in older D40A dozers that remain in active service. Its simplicity and availability of aftermarket support make it a staple for fleet managers maintaining legacy earthmoving equipment. The transition to the S4D105-3 introduced further emissions adjustments, but the 2B series remains a critical reference point for parts interchangeability and overhaul procedures in the mid-size dozer segment.
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 S4D105-2B(S/N 18273-UP) specifications
Engine
| Model | S4D105-2B |
| Serial Range | 18273-Up |
| Displacement | 10.5 L (640.8 cu. in.) |
| Cylinders | 4 |
| Emissions Tier | Not documented for this exact serial range — verify with your dealer |
| Gross/Net Power | 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 |
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 S4D105-2B(S/N 18273-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 S4D105-2B(S/N 18273-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 at 500 hours to prevent liner cavitation in the S4D105-2B block. Monitor hydraulic oil particle count and viscosity at 1,000 hours to detect pump wear early. Track fuel dilution and soot levels in the engine oil to assess combustion efficiency and filter life. Use KOMTRAX telematics to correlate load frequency with fluid degradation rates for accurate interval adjustments.
Corrective & Common Repairs
Address frequent S4D105-2B issues by inspecting the Type T04B turbocharger shaft play and seal integrity during 1,000-hour services. Check the fuel injection pump governor linkage for wear, which can cause erratic engine speeding. Inspect the cylinder head gasket for coolant leaks, a common failure point in high-hour D40A applications. Replace worn piston rings if compression drops, noting the S4D105-2B uses special cast iron ring groove inserts. Verify the condition of the fuel feed pump and spill pipes to prevent air ingress and hard starting.
Overhaul & Rebuild Points
Plan the S4D105-2B inframe overhaul around 10,000 to 15,000 hours, focusing on the piston, rings, and cylinder liner wear limits. Replace the turbocharger bearings and seals if boost pressure drops below specification. Inspect the crankshaft main and rod bearings for clearance exceeding factory tolerances. Check the cylinder head for warpage and valve seat wear. Use Komatsu S4D105-1 & 2 series specific inframe overhaul kits to ensure proper fitment of gaskets, seals, and bearings for this serial range.
Seasonal & Environment Servicing
In cold climates, ensure the S4D105-2B thermostart system functions correctly for easy starting. Use Komatsu Super Coolant AF-NAC with the correct glycol mix to prevent freezing and overheating. In dusty environments, service the air pre-cleaner and outer air filter element more frequently to protect the turbocharger and intake valves. Check the radiator and oil cooler fins for debris buildup to maintain optimal heat rejection. Inspect the battery and alternator for corrosion in high-humidity or coastal operating conditions.
S4D105-2B(S/N 18273-UP) common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| 6130-71-6102 | Fuel Filter Ass'Y | Fuel system service | Check fitment → |
| 07000-02075 | O-Ring,Steering Oil Filter | Lubrication service | Check fitment → |
| 6130-51-5103 | Oil Filter Ass'Y | Lubrication service | Check fitment → |
| 600-181-8210 | Element,Outer | Scheduled service item | Check fitment → |
| 600-181-8310 | 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.
S4D105-2B(S/N 18273-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 |
| CA451 | Common rail pressure sensor feedback value too high | Malfunction in the rail pressure sensor or 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 in the intake system | Check for a sensor short or inspect for airflow restrictions |
| 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 or circuit issue | Replace or test the IAT sensor |
| CA441 | Battery voltage too low | Weak battery, failing alternator, or voltage regulator issue | Replace the alternator or battery and check the voltage regulator |
| CA442 | Battery voltage too high | Failing alternator or voltage regulator causing overcharging | Replace the alternator or battery and check the voltage regulator |
| CA234 | Engine overspeed | Throttle calibration error, engine load cycle issue, or operator misuse | Verify throttle calibration and review engine load cycle |
| AA10NX | Air cleaner clogging | Dirty or blocked air filter element | Replace the air filter element |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
S4D105-2B(S/N 18273-UP) attachments & work tools
Crawler Dozer Blade Systems
The S4D105-2B engine (S/N 18273-Up) powers the D40A-1 / PL-1 dozer series. Factory configurations for this class typically include standard straight or angle dozer blades with hydraulic tilt or angle options. Guarding options often involve side cutters and rear guards to protect the undercarriage during heavy pushing operations.
Hydraulic Excavator Attachments
This engine class is associated with the PC100, PC120, and PC150 excavator families. Standard work tools include digging buckets ranging from 0.3 to 0.6 cubic meters, depending on the specific machine model (e.g., PC100-1 vs PC120-2). Hydraulic breaker and hammer kits are available, requiring high-flow auxiliary hydraulic lines and specific control valve arrangements.
Motor Grader Implements
The S4D105-2B is listed in equipment guides for the GD200A-1 and GD300A-1 motor grader series. Primary work tools include moldboard blades with straight or angle configurations and scarifiers for soil loosening. Coupler systems for these implements are integrated into the frame, with hydraulic adjustments for pitch and tilt.
Wheeled Loader Buckets
Applications for this engine include the GD405A-1 and GD500R-2A wheel loader models. Typical work tools are general-purpose and light material buckets with capacities varying by model size. Quick-attach coupler systems allow for the swapping of buckets for forks or other handling attachments, supported by standard auxiliary hydraulic circuits.
All S4D105-2B(S/N 18273-UP) assemblies by section
Every catalogued assembly group for the Komatsu S4D105-2B(S/N 18273-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Cooling And Electrical Systems
Komatsu : S4d105-2b(S/N 18273-Up) : Cooling And Electrical Systems : Alternator
| 60***50 | Alternator A. (13a),(With Non Hardening Pulley) | 1 |
| KD***30 | Holder,Brush | 1 |
| KD***80 | Packing | 1 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cooling And Electrical Systems : Alternator (800w)
| 60***70 | Alternator A | 1 |
| KD***40 | Front Bracket A | 1 |
| KD***80 | Plate | 2 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cooling And Electrical Systems : Alternator And Mounting
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 1 |
| 01***40 | Bolt,(Dust And Dirt Protection) | 1 |
| 01***55 | Bolt,(For Suction? Reversible Fan) | 1 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cooling And Electrical Systems : Safety Relay And Resistor
| 60***30 | Resistor | 1 |
| 60***10 | Alternator A | 1 |
| 60***10 | Regulator Ass'Y,For 35a Alternator (Not Shown) | 1 |
Komatsu : S4d105-2b(S/N 18273-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 |
| 60***70 | Starting Motor A.,(See Fig.545) | 1 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cooling And Electrical Systems : Starting Motor(#.-)
| 60***71 | Starting Motor A | 1 |
| KD***10 | Clutch Ass'Y,Over Running | 1 |
| KD***80 | Shift Lever Ass'Y | 1 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cooling And Electrical Systems : Starting Motor(#18273-.)
| 60***70 | Starting Motor A.,(See Fig.545) | 1 |
| KD***90 | Cover | 1 |
| KD***90 | Center Bracket A | 1 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cooling And Electrical Systems : Water Pump And Cooling Fan
| 01***20 | Bolt,(Sandy? Dusty Terrain Spec.) | 2 |
| 01***25 | Bolt,(Without Auto Priming System) | 8 |
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 6 |
Cylinder Block
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Block : Balancer Shaft
| 01***20 | Bolt,(Sandy? Dusty Terrain Spec.) | 4 |
| 01***25 | Washer,Spring?(Sandy And Dusty Spec.) | 4 |
| 04***19 | Key,(Dk025805-1910) | 1 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Block : Camshaft And Tappet
| 01***20 | Bolt,(Sandy? Dusty Terrain Spec.) | 2 |
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 1 |
| 01***25 | Washer,Spring?(Sandy And Dusty Spec.) | 2 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Block : Crankshaft And Timing Gear
| 01***30 | Bolt,(For France Noise Suppression) | 4 |
| 02***04 | Plug,(Not Shown) | 4 |
| 04***25 | Key | 1 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Block : Cylinder Block
| 01***55 | Bolt,(For Suction? Reversible Fan) | 4 |
| 01***65 | Bolt | 3 |
| 04***14 | Pin, Dowel | 2 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Block : Flywheel And Flywheel Housing
| 01***14 | Bolt | 3 |
| 01***18 | Bolt | 6 |
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 17 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Block : Front Cover And Support
| 01***12 | Bolt,(Without R.P.C.U.) | 2 |
| 01***22 | Bolt | 2 |
| 01***45 | Bolt,(For Suction? Reversible Fan) | 10 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Block : Oil Pan
| 01***16 | Bolt,(For Slag Handling) | 2 |
| 01***20 | Bolt,(Large Capacity Type) (Std) | 1 |
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 28 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Block : Piston And Connecting Rod
| 61***15 | Bolt,(Service Parts) | 2 |
| 61***22 | Nut,(Service Parts) | 2 |
| 61***30 | Washer,(Service Parts) | 2 |
Cylinder Head
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Head : Air Intake Connection And Air Cleaner
| 01***22 | Bolt,(Cold Terrain Spec.) | 3 |
| 01***25 | Bolt,(Without Auto Priming System) | 4 |
| 01***30 | Bolt,(Cold Terrain Spec.) | 3 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Head : Compression Release
| 01***20 | Bolt,(Sandy? Dusty Terrain Spec.) | 1 |
| 01***25 | Bolt,(Without Auto Priming System) | 1 |
| 01***05 | Nut (Welded) | 1 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Head : Cylinder Head
| 01***16 | Bolt,(For Slag Handling) | 6 |
| 01***35 | Stud | 8 |
| 01***25 | Washer,Spring?(Sandy And Dusty Spec.) | 6 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Head : Cylinder Head Cover
| 01***22 | Bolt,(Cold Terrain Spec.) | 10 |
| 01***20 | Bolt,(Large Capacity Type) (Std) | 1 |
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 2 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Head : Exhaust Manifold And Muffler
| 01***35 | Stud | 1 |
| 01***11 | Nut (M14-1.50 Thd), Nut; Was 01582-01411 | 2 |
| 01***25 | Washer,Spring?(Sandy And Dusty Spec.) | 2 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Head : Rocker Arm And Housing
| 01***12 | Bolt,(Without R.P.C.U.) | 1 |
| 01***20 | Bolt,(Sandy? Dusty Terrain Spec.) | 4 |
| 01***85 | Bolt | 15 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Head : Turbocharger (Except Japan)
| 61***01 | Turbocharger Ass'Y,(See Fig.141) | 1 |
| 61***02 | Turbocharger Ass'Y,(See Fig.141) | 1 |
| 61***03 | Turbocharger Ass'Y,(See Fig.141) | 1 |
Komatsu : S4d105-2b(S/N 18273-Up) : Cylinder Head : Water Pipe And Thermostat
| 01***18 | Bolt | 3 |
| 01***22 | Bolt,(Cold Terrain Spec.) | 9 |
| 01***35 | Bolt,(Without Auto Priming System) | 3 |
Fuel System
Komatsu : S4d105-2b(S/N 18273-Up) : Fuel System : Fuel Filter And Mounting
| 01***35 | Bolt, Mounting - Flywheel Housing End | 2 |
| 01***30 | Washer,Spring(Sandy?Dusty Terrain S.) | 2 |
| 07***12 | Gasket,Mechanical Pump Piping | 1 |
Komatsu : S4d105-2b(S/N 18273-Up) : Fuel System : Fuel Injection Pump (Feed Pump)
| 61***10 | Injection Pump A.,(See Fig.451) | 1 |
| 61***11 | Injection Pump A | 1 |
| DK***20 | Housing | 1 |
Komatsu : S4d105-2b(S/N 18273-Up) : Fuel System : Fuel Injection Pump (Governor)
| 61***10 | Injection Pump A.,(See Fig.451) | 1 |
| DK***00 | Adapter | 1 |
| DK***20 | Capsule,Spring | 1 |
Komatsu : S4d105-2b(S/N 18273-Up) : Fuel System : Fuel Injection Pump (Pump)
| 61***10 | Injection Pump A.,(See Fig.451) | 1 |
| 61***11 | Injection Pump A | 1 |
| DK***00 | Shim? 0.85mm | 0 |
Komatsu : S4d105-2b(S/N 18273-Up) : Fuel System : Fuel Injection Pump And Piping
| 01***16 | Bolt (Welded) | 1 |
| 01***18 | Bolt | 4 |
| 01***20 | Bolt,(Sandy? Dusty Terrain Spec.) | 10 |
Komatsu : S4d105-2b(S/N 18273-Up) : Fuel System : Fuel Nozzle And Spill Pipe
| 01***65 | Bolt | 8 |
| 07***12 | Gasket,Mechanical Pump Piping | 6 |
| 07***37 | Clamp, Overflow Hose | 2 |
Komatsu : S4d105-2b(S/N 18273-Up) : Fuel System : Thermostat And Piping(#18273-25354)
| 01***12 | Bolt (M8-1.25x12) | 3 |
| 01***22 | Bolt,(Cold Terrain Spec.) | 3 |
| 01***25 | Washer,Spring?(Sandy And Dusty Spec.) | 6 |
Komatsu : S4d105-2b(S/N 18273-Up) : Fuel System : Thermostat And Piping(#25355-)
| 01***25 | Bolt,(Without Auto Priming System) | 2 |
| 01***05 | Nut (Welded) | 2 |
| 01***19 | Washer,(Not Used With Ventilator) | 2 |
Lubricating Oil System
Komatsu : S4d105-2b(S/N 18273-Up) : Lubricating Oil System : Lubricating Oil Cooler
| 01***35 | Bolt, Mounting - Flywheel Housing End | 8 |
| 01***08 | Screw | 4 |
| 01***08 | Nut,R.H. Thread | 4 |
Komatsu : S4d105-2b(S/N 18273-Up) : Lubricating Oil System : Lubricating Oil Filter
| 01***30 | Bolt,(For France Noise Suppression) | 1 |
| 01***80 | Bolt, Mount Strainer Flange | 2 |
| 01***04 | Nut | 2 |
Komatsu : S4d105-2b(S/N 18273-Up) : Lubricating Oil System : Lubricating Oil Pump
| 01***16 | Bolt,(For Slag Handling) | 2 |
| 01***20 | Bolt,(Sandy? Dusty Terrain Spec.) | 1 |
| 01***25 | Bolt,(Without Auto Priming System) | 2 |
Komatsu : S4d105-2b(S/N 18273-Up) : Lubricating Oil System : Lubricating Oil Strainer
| 01***22 | Bolt | 2 |
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 4 |
| 01***55 | Bolt,(For Suction? Reversible Fan) | 3 |
Komatsu : S4d105-2b(S/N 18273-Up) : Lubricating Oil System : Turbocharger Lubricating Oil Piping
| 01***20 | Bolt,(Sandy? Dusty Terrain Spec.) | 2 |
| 01***22 | Bolt,(Cold Terrain Spec.) | 2 |
| 01***25 | Washer,Spring?(Sandy And Dusty Spec.) | 4 |
Tool And Kit
Komatsu : S4d105-2b(S/N 18273-Up) : Tool And Kit : Gasket Kit
| 01***12 | Washer,Lock (K2) | 1 |
| 01***08 | Washer,Lock (Kit) | 1 |
| 01***16 | Washer,Lock (K2) | 1 |
S4D105-2B(S/N 18273-UP) serial number reference
The engine serial number plate is located on the left side of the engine block or on a metal data plate affixed near the valve cover. The prefix 'S4D105-2B' identifies the engine model, while the number following it (starting at 18273) indicates the build sequence within that engine family.
| Prefix | Identifies | Notes |
|---|---|---|
| S4D105-2B | Engine Model | Identifies the S4D105-2B engine family. Serial range 18273-UP is explicitly tied to this engine model in factory parts catalog listings and equipment guides. This engine is used in Komatsu D40A-1 / PL-1 dozers (S/N 1501-Up) and other equipment in the 105 series. No specific 3-character PIN prefixes are listed for this engine range in the provided sources; the engine model code itself serves as the primary identifier for parts cataloging. |
Frequently asked questions
What engine does the Komatsu S4D105-2B power?
The S4D105-2B is a four-cylinder, turbocharged diesel engine used in the D40A-1 and PL-1 crawler dozer series.
What is the operating weight of the D40A-1 dozer?
The operating weight of the D40A-1 dozer varies by configuration, typically ranging from 15,000 to 20,000 lbs.
What engine replaced the S4D105-2B?
The S4D105-3 series engine replaced the S4D105-2B, with the transition occurring at engine serial number 44579.
Need a specific S4D105-2B(S/N 18273-UP) part?
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