Key Takeaways
- The Mitsubishi S4S is a 4-cylinder, 3.3-liter industrial diesel engine used in forklifts, generators, and construction machinery from the 1990s through today.
- Core specs include a bore of 94mm, stroke of 120mm, naturally aspirated design, and power output ranging from 37.5–49.7 kW (50–67 hp) depending on configuration.
- The S4S delivers strong torque at low RPM, low fuel consumption, and quiet operation—ideal for indoor and urban industrial applications.
- Quality spare parts and overhaul kits from Fab Heavy Parts help extend engine life and reduce total cost of ownership.
- This guide covers technical specifications, common applications, maintenance tips, and how to buy the right S4S engine components.
Introduction to the Mitsubishi S4S Motor
The Mitsubishi S4S motor is a workhorse diesel engine built by Mitsubishi Heavy Industries for demanding industrial applications. Since the 1990s, this reliable 4-cylinder powerplant has become a popular choice in forklifts, wheel loaders, and mid-size generators worldwide.
This guide is intended for equipment owners, mechanics, and buyers who need reliable information on the Mitsubishi S4S engine for maintenance, repair, or purchasing decisions. Understanding the S4S engine is crucial for making informed choices about equipment upkeep, troubleshooting, and parts sourcing.
Fab Heavy Parts specializes in heavy equipment components, including Mitsubishi S4S engine parts and rebuild kits. Read on to learn the specs, common trouble spots, and how to source quality components to keep your S4S-powered machines running strong.
Mitsubishi S4S Engine Overview
The S4S belongs to Mitsubishi’s S-series of industrial engines, designed for compact packaging and extended service life. It’s a 4-stroke, inline 4-cylinder diesel—naturally aspirated in most versions—built for continuous-duty work across multiple industries.
The Mitsubishi S4S is a 4-cycle, water-cooled, inline 4-cylinder industrial diesel engine in the 3.3-liter to 3.4-liter class.
What makes it “industrial”? The engine runs many hours per day at steady RPM, prioritizing durability over peak horsepower. Compared to smaller Mitsubishi engines like the SL or SQ series, the S4S delivers more torque and displacement for heavier machines.
Mitsubishi S4S Technical Specifications
Core Engine Specs
Here are the core factory specs equipment owners and mechanics ask about most:
- Configuration: 4-cylinder, inline, 4-stroke diesel, OHV
- Displacement: 3.331 liters (203 cubic inches)
- Bore and Stroke: 94mm bore × 120mm stroke (3.7” × 4.7”)
- Aspiration: Naturally aspirated (turbocharged versions exist for specific OEMs; the S4S engine supports both naturally aspirated and turbocharged variants.)
- Combustion System: Indirect injection with swirl chamber for cleaner, quieter operation
- Cooling System: Water-cooled with belt-driven fan
- Power Output: 37.5–49.7 kW (50–67 hp) at 1,500–2,500 RPM, depending on calibration
- Max Torque: Approximately 182 Nm at peak
- Compression Ratio: 17:1
- Fuel Type: No. 2 diesel
- Dry Weight: 245–250 kg (540–551 lbs)
Additional Notes
Specs vary by OEM application. Contact Fab Heavy Parts with your serial number to confirm exact part matches.
Performance, Fuel Economy & Noise Characteristics
The S4S balances strong torque, efficient fuel burn, and smooth operation for heavy-duty work. This engine excels at low-RPM tasks: lifting, pushing, and driving hydraulic pumps.
Fuel Efficiency and Noise
Fuel efficiency is a standout feature. At full load, specific fuel consumption runs around 255 g/kWh—competitive for this class. The indirect injection and swirl chamber design help the engine burn fuel more completely, reducing visible smoke.
Noise matters in warehouses and urban sites. The S4S uses optimized combustion timing and a stiff cast-iron block to keep vibration and sound levels manageable indoors.
Common Applications of the Mitsubishi S4S Motor
The S4S powers equipment from multiple OEMs across material handling and construction. Here’s where you’ll find it:
- Forklifts: Mitsubishi, Caterpillar, and Komatsu lift trucks in the 2–3.5 ton range
- Construction Machines: Small wheel loaders, skid steers, and compact rollers
- Generators: Mid-size industrial gensets in the 20–40 kW class for sites and rental fleets
- Pumps and Compressors: Dewatering pumps and hydraulic power packs needing continuous-duty diesel power
Because OEMs adapt the same S4S block differently, accessories like oil pans, manifolds, and mounts can vary. Have your engine model and serial number ready when you order Mitsubishi S4S engine parts.
Reliability, Durability & Total Cost of Owndership
The S4S has earned its reputation as a reliable engine. With proper maintenance, many units exceed 10,000 working hours in forklifts and generators.
Design choices support this longevity: robust cast-iron construction, conservative RPM limits, and simple mechanical fuel systems on many versions. These features translate to fewer major failures, good parts availability, and affordable rebuild options.
Quality components from stock at Fab Heavy Parts help you avoid repeat failures. Cheap pistons or gaskets can shorten engine life dramatically, and understanding piston replacement costs and procedures as well as piston slap causes and remedies can prevent avoidable damage.
Maintenance Tips & Common Problem Areas
Routine Maintenance
Routine service separates an S4S that fails early from one that runs for years. Follow these guidelines:
- Oil and Filters: Change oil every 250 hours in heavy use. Oil capacity is 10 liters.
- Fuel System: Replace fuel filters regularly. Drain water separators to protect injectors.
- Cooling System: Check coolant level, hose condition, and radiator cleanliness.
- Air Filter: Inspect frequently in dusty environments to prevent cylinder wear.
Common Problem Areas
Common trouble spots include:
- Hard starting or rough idle from worn injectors
- Overheating from clogged radiators or stuck thermostats
- Oil leaks around main seals and rocker cover gaskets
- Loss of power from poor compression or dirty intake
Catch issues early. Strange noises or increased oil consumption should trigger inspection before failure.
Mitsubishi S4S Engine Parts, Rebuild Kits & Long Blocks
Fab Heavy Parts supplies quality components matched to S4S applications and other Mitsubishi diesel platforms such as:
- 4D33 engine parts
- 4D34 engine parts
- 4D55 engine components
- 4D56 engine parts
- 4M40 engine components
- 6D15 engine parts
- K4N engine parts
- L3E engine components
- S3L engine parts
- S4E engine parts
- S4L engine components
- S4Q engine parts
- Complete Overhaul Kits: Pistons, rings, liners, bearings, gaskets, and seals
- Cylinder Head Components: Valves, guides, springs, and hardware
- Wear Items: Oil pumps, water pumps, belts, and gasket sets
- Fuel System Parts: Injectors and injection pump seals
- Ancillary Parts: Starters, alternators, and engine mounts
For larger repairs, remanufactured S4S long blocks reduce downtime compared to in-frame rebuilds. Using a complete overhaul kit ensures matched components and fewer ordering errors.
Contact the team via phone or through fabheavyparts.com with your serial number for perfect parts matching.
Why Choose Fab Heavy Parts for Your Mitsubishi S4S Motor Needs
Fab Heavy Parts focuses on heavy-duty industrial applications. Our team knows forklift and construction applications of the S4S inside and out.
We help you identify the correct S4S version using photos, serial tags, and OEM references, and we also stock Isuzu 4LE2 engine parts and other major diesel platforms. Fast delivery across North America keeps your equipment running. Learn more about Fab Heavy Parts and our service standards or visit fabheavyparts.com to get a quote on overhaul kits, individual parts, or long block options.
FAQ
Q1: How do I identify which Mitsubishi S4S version I have?
A1: Look for the engine data plate on the side of the block or valve cover area. It shows model, serial number, and output rating. Different OEMs use slightly different S4S variants, so note your equipment model too. Send photos of the data plate to Fab Heavy Parts to verify correct parts.
Q2: What type of engine oil should I use in a Mitsubishi S4S?
A2: Use high-quality diesel engine oil meeting OEM specifications—typically 15W-40 for most climates. Verify against your machine’s manual. Oil choice may change for extreme cold or hot environments. Pair proper oil with filter changes at recommended hour intervals.
Q3: How many hours can a Mitsubishi S4S motor last before overhaul?
A3: Expect 8,000–12,000 hours under good maintenance, with some engines exceeding that in light-duty applications. Operating conditions like dust, load, and service history affect actual life. Low compression, high oil consumption, and hard starting signal it’s time for an overhaul kit or long block.
Q4: Can the Mitsubishi S4S meet modern emissions requirements?
A4: Many S4S engines predate current emissions tiers and are used where older standards apply. Later versions meet EU Stage IIIA without complex aftertreatment like DPF or SCR. Check local regulations before deploying S4S-powered equipment in strict emissions zones.
Q5: Should I rebuild my S4S or replace it with a remanufactured long block?
A5: In-frame rebuilds work well if the block and crank are sound and your shop has experience. Remanufactured long blocks save labor time and reduce downtime for busy fleets. Fab Heavy Parts can help you weigh both options based on engine condition and budget.
FAB Heavy Parts: Your Trusted Engine Parts Supplier
Welcome to Fab Heavy Parts' online catalog, your trusted source for quality auto parts and tools. Explore our extensive selection of Replacement Parts for Mitsubishi S4S and more. Avoid delays by securing the parts you need from a reliable supplier who keeps inventory moving. Our expert team is here to provide personalized support, ensuring you get the right parts. Reach out today to stay ahead and keep your operations seamless!