The Complete, Extended Guide to Mitsubishi Excavator Engines

Range, Specs, Applications, Maintenance, and Buying Tips

When you look under the hood of many Japanese excavators — and quite a few Korean and European machines — there’s a good chance you’ll find a Mitsubishi engine quietly doing its job. Mitsubishi’s industrial diesel range has earned a reputation for reliability, simplicity, torque-rich performance, and long service life. Whether you’re running a 1.5-ton mini excavator or a 20-ton earth-mover, Mitsubishi has produced an engine for that class.

This extended guide dives into the full spectrum of Mitsubishi excavator engines, including the well-known S-Series, D-Series, and 6-cylinder heavy-duty units. We’ll walk through typical specs, machine applications, key differences between models, maintenance realities, failure signs, and what to look for when buying used or replacement engines.

By the time you finish this guide, you’ll understand the Mitsubishi engine landscape well enough to make informed repair, replacement, or upgrade decisions.

1) Mitsubishi Excavator Engine Families: Extended Overview

Mitsubishi has built industrial engines for decades, but only a portion of their catalogue is commonly found in excavators. The engine families most frequently installed in construction equipment fall into three broad ranges:

A) Compact Models (Mini Excavators — 1–3 Tons)

These engines are typically 2–3 cylinder units, mechanically injected, compact, and extremely service-friendly. Many older mini excavators from manufacturers like Mitsubishi, Sumitomo, early Kobelco units, and some Chinese brands use these engines.

Typical benefits:

• Lightweight design

• Low fuel consumption

• Simple mechanical injection

• Easy cold starts

• Minimal electronics, ideal for harsh job sites

The smaller engines from the L-series and S3 variants dominate this range.

B) Mid-Range Models (3–10 Tons)

This is the heart of Mitsubishi’s excavator presence. The S-Series (especially the S4S and S4SD) and the 4D-Series (4D31, 4D32, 4D34, 4D36) power a huge number of mid-sized excavators across global brands.

These mid-range engines are famous for:

• Strong low-RPM torque

• Great fuel efficiency

• Long engine life (often 8,000–15,000 hours when maintained)

• Excellent parts support

• Low smoke emission compared to many older diesels

• Affordable rebuild costs

Machines in the 5–10 ton class are almost always paired with 4-cylinder diesels, which makes this range arguably the most important for contractors and independent operators.

C) Heavy-Duty Models (10+ Tons)

When machines get bigger, the hydraulic demands get higher — and that’s where Mitsubishi’s six-cylinder workhorses step in. The 6D-Series (like the 6D34) and the S6 series are built for continuous duty, thermal stability, and delivering torque you can trust all day.

These engines appear in:

• Large excavators

• Material handlers

• Pipe layers

• Track loaders

• Logging machinery

• Articulated equipment

If you’re running big iron, six cylinders and long service intervals matter — and Mitsubishi engines deliver both.

2) Deep Dive Into Key Mitsubishi Excavator Engines

Below is a deeper, more detailed look at individual Mitsubishi engines you’ll encounter most often.

S-Series (S3, S4S, S6S)

These are among Mitsubishi’s most widespread industrial engines.

S4S — The Legendary Mid-Size Performer

• Cylinders: 4

• Displacement: ~3.3 L

• Bore x Stroke: 94 × 120 mm

• Power Output: ~47–62 kW depending on configuration

• Injection: Mechanical

• Aspiration: NA or Turbo

Why excavator manufacturers love it:

• Strong low-end torque makes hydraulic operation smoother

• Easy to rebuild

• An enormous global parts supply

• Proven to run 10,000+ hours with basic care

Suitable for 3–8 ton excavators.

S6S — Smooth, Strong, and Reliable

• Cylinders: 6

• Power Output: ~65–90 kW

• Displacement: ~4.9–5.0 L

Known for long life, smooth operation and excellent thermal stability. A favourite for larger machines and continuous-duty environments.

D-Series (4D31, 4D32, 4D34, 4D36, 6D34)

The D-Series covers a huge range of 4-cylinder and 6-cylinder engines that power medium to large excavators.

4D34 — The Mid-Size Workhorse

• Cylinders: 4

• Displacement: ~3.9 L

• Power: 70–90 kW depending on tune

• Torque: Strong mid-range torque, excellent for heavy digging

• Applications: 8–12 ton excavators

The 4D34 is known for great parts support, brilliant torque delivery, and incredible reliability in dusty or extreme climates.

4D36 — Big Brother to the 4D34

A slightly larger and more powerful version, often used in 10+ ton equipment.

6D34 — The Big Machine Engine

• Cylinders: 6

• Displacement: ~7.5 L

• Power: 120+ kW depending on the configuration

• Applications: 12–20+ ton excavators, heavy equipment

This engine delivers:

• Strong sustained torque

• Better cooling capacity

• Service intervals suitable for high-duty cycles

3) Turbocharged vs Naturally Aspirated Mitsubishi Engines

Nearly every Mitsubishi excavator engine comes in both NA (natural) and turbocharged variants.

Naturally Aspirated engines deliver:

• Simpler design

• Fewer failure points

• Better fuel economy

• Lower cost to maintain

Turbocharged engines offer:

• More torque at lower RPM

• Better throttle response under hydraulic load

• Improved performance on heavy digging cycles

For mid-size to heavy excavators, turbo variants are almost always preferred.

4) Emission Standards and Control Systems

Older Mitsubishi engines are famously simple — mechanical pumps, low electronics, easy diagnostics.But newer versions (especially late-model 4D engines) may include:

• ECU-controlled fuel timing

• Electronic injection

• Newer emissions packages (depending on region)

If swapping engines, pay special attention to emission requirements in your country or province.

5) Maintenance: What Fails, What Lasts, and What to Watch For

Mitsubishi engines are consistent and predictable — when something goes wrong, it’s almost always one of a short list of culprits.

Common Wear Points

1. Injectors & fuel pump — dirty diesel = rough running

2. Turbocharger — oil seal leaks or blade wear

3. Cooling system — clogged radiators in dusty sites

4. Head gasket — usually linked to overheating

5. Valves & valve stem seals — especially on high-hour units

6. Engine mounts — oil-soaked or cracked cushions

Tell-tale Symptoms of Trouble

• Black smoke: overfueling or poor air intake

• Blue smoke: oil burning (rings/valves/turbo)

• White smoke: coolant in combustion

• Power loss: timing, injection, or turbo issues

• Overheating: cooling system blockage

6) Mitsubishi Engine Longevity (What Affects Engine Life)

With proper care, Mitsubishi engines consistently hit:

• 5,000 hours with minimal issues

• 8,000–12,000 hours with good maintenance

• 15,000+ hours if rebuilt mid-life

Key factors affecting lifespan:

• Fuel quality

• Cooling system health

• Oil type and change intervals

• Dust control

• Regular valve adjustments

7) Buying a Used or Rebuilt Mitsubishi Engine — Extended Checklist

If you’re shopping for a replacement engine, here are the extended checks to perform:

A) Visual & Physical Checks

• Match engine model and serial number

• Confirm pump drive compatibility

• Check engine mounts

• Inspect for cracks, welds, or patch repairs

• Check oil and coolant condition

B) Performance Checks

• Perform a compression test

• Listen for piston slap

• Cold start behavior

• Look for excessive smoke

• Check blow-by levels

C) Compatibility Checks

• Flywheel housing match

• ECU requirements (if applicable)

• Turbo layout & plumbing

• Radiator compatibility

• Alternator and starter orientation

A cheap engine becomes expensive very quickly if even one component doesn’t fit your excavator.

8) Engine Swaps: What You Must Consider

Mitsubishi engines are often swapped between different excavator brands, but success depends on careful planning.

Critical Swap Requirements:

• Correct bellhousing pattern

• Hydraulic pump mount compatibility

• Engine RPM and torque curve match

• Exhaust and intake alignment

• Wiring harness compatibility

• Cooling system size

• Fuel pump calibration

Never assume “if it bolts in, it will work.” Hydraulics depend on precise engine characteristics.

9) Parts Availability and Support

One of the biggest strengths of Mitsubishi engines is the global availability of parts.You can find:

• Rebuild kits

• Injectors and pumps

• Head gaskets

• Pistons and liners

• Bearings

• Water pumps & thermostats

• Turbochargers

• Complete refurbished engines

This makes Mitsubishi an excellent long-term ownership choice — parts remain accessible even for older engines.

10) Which Mitsubishi Engine is Right for Your Excavator?

Here’s the final breakdown:

Mini Excavators (1–3 tons)

→ Mitsubishi S3 / small L-SeriesChoose for: simplicity, lightweight design, low fuel consumption

Mid-Size Excavators (3–10 tons)

→ Mitsubishi S4S / S4SD / 4D34Choose for: torque, reliability, affordable parts

Large Excavators (10+ tons)

→ Mitsubishi S6S / 6D34Choose for: continuous power, cooling stability, durability

Conclusion

Mitsubishi engines have earned their place in excavators worldwide thanks to their reliability, simple design, strong torque delivery, and excellent long-term support. Whether you're maintaining a fleet or replacing a single engine, understanding the Mitsubishi engine range helps you make better, more cost-effective decisions.

If you need a version tailored specifically for Vikfin, emphasising used parts sourcing, rebuilds, and South African conditions, I can create that version too.

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