Buying a Mitsubishi S3L & S4L Diesel Engine: The Complete Purchasing Guide

Buying a Mitsubishi S3L & S4L Diesel Engine: The Complete Purchasing Guide

Want to buy a Mitsubishi S3L or S4L diesel engine, or are you unsure whether an S3L2 or S4L2 would suit your machine better? Then this purchasing guide will help you out. These four-stroke swirl chamber engines are compact, reliable, and can be found in hundreds of mini tractors, forklifts, excavators and boats — but there are real differences between the four types in cylinder count, displacement and power that determine what you can do with them.

Suitable for the entire series: Mitsubishi S3L, S3L2, S4L and S4L2 — found in, among others, Vetus, Solé Diesel, Caterpillar, Pel-Job, Weidemann, Terex, Atlas, Deutz, Bobcat, Mahindra, Solis, TYM and Farmtrac.

Mitsubishi S3L & S4L: which engine do you have?

The type designation is logically structured. The S stands for Sagamihara (the factory), the number indicates the number of cylinders (3 or 4), the L refers to the cylinder family with a 78 mm bore, and an optional 2 indicates the second version with a longer stroke. That's where the key difference lies:

• S3L and S4L have a short stroke of 78.5 mm.
• S3L2 and S4L2 have a longer stroke of 92 mm — meaning more displacement and torque from the same block.
• S3L/S3L2 are 3-cylinders, S4L/S4L2 are 4-cylinders with the same bore.

Because the stroke differs between the "1" and "2" versions, the pistons and most gaskets are not simply interchangeable between, for example, an S4L and an S4L2. So always order parts based on the exact type, not just "S4L".

Specifications per model (from the workshop manual)

*Power output is not listed in the workshop manual, as it depends on the application and the permitted engine speed. The hp figures above are indicative and intended to help position the models relative to each other; the manufacturer of your machine determines the exact power output. All other technical data comes directly from the Mitsubishi workshop manual.

Mitsubishi S3L & S4L: what is this engine used in?

The strength of this series lies in its enormous range of applications. In practice, you'll find it as an industrial engine in Caterpillarmini excavators and wheel loaders, in Pel-Job, Weidemann, Terex and Atlas, as a marine engine under the brand names Vetus and Solé Diesel, and as a tractor engine in, among others, Mahindra, Solis, TYM and Farmtrac. That same block may therefore have been sold under dozens of brand names — good to know, since parts for "your" machine are often simply Mitsubishi parts.

Buying a Mitsubishi S3L & S4L: what to check before purchase

If you're buying a complete engine or a machine with this engine in it, go through these points:

• Cold starting. A healthy swirl chamber engine with good glow plugs starts easily from cold, without endless cranking. Long cranking times, lots of white smoke, and the engine only catching after half a minute point to wear, faulty injectors or weak glow plugs.
• Smoke color. Blue smoke = oil consumption (piston rings, valve guides). Persistent white smoke = injection issues or a leaking head gasket. Black smoke under load = fuel/injection issues or the air filter.
• Compression and head gasket. At 22.0 : 1, good compression is crucial. Check for oil in the coolant and water/exhaust gases in the oil — classic signs of a damaged head gasket or a crack between the swirl chambers.
• Oil and coolant. Mayonnaise-like residue under the filler cap, an overfilled oil level, or a diesel smell in the oil are warning signs. Ask about the maintenance history and the type of oil used (CD grade or better).
• Injection pump and injectors. The injection pump and governor are covered in a separate manual and are a specialist (and pricey) component. An engine running poorly due to worn injectors or a maladjusted pump can turn into an expensive surprise.
• Getting the type and year of manufacture right. Due to all the rebadging, confusion between S3L/S3L2 and S4L/S4L2 (and with the older "1" versions) is not uncommon with grey imports. Check the type plate and, if possible, the engine number before ordering parts.

Strengths and weaknesses — honestly assessed

Strong points: a simple, cast-iron block that can rack up plenty of running hours, wide parts availability, easy to overhaul, and relatively quiet for a diesel in this class. The swirl chamber technology is forgiving and runs smoothly.

Weak points: as an indirect-injection engine, it needs good glow plugs to start easily from cold, and oil consumption increases once the piston rings or valve guides wear out. The injection components are expensive to overhaul. Also note: power and torque are modest, so choose deliberately between a 3- and 4-cylinder based on what you'll actually be using it for.

Frequently asked questions about the Mitsubishi S3L & S4L

What is the difference between an S4L and an S4L2?

Both are 4-cylinders with a 78 mm bore, but the S4L2 has a longer stroke (92 mm instead of 78.5 mm) and therefore more displacement — 1.758 liters versus 1.500 liters. The S4L2 therefore delivers more torque. Pistons and various gaskets differ, so always order based on the exact type.

How much horsepower does a Mitsubishi S3L or S4L have?

That depends on the application and the engine speed the machine manufacturer has set it to. As an indication, an S3L is around 16–20 hp, an S3L2 around 21–28 hp, an S4L around 24–30 hp, and an S4L2 around 30–38 hp. The workshop manual does not list a fixed horsepower figure.

Are parts for the S3L and S4L still readily available?

Yes. Because the engine is used in so many brands and machines, cylinder heads, gasket sets, overhaul kits, pistons, bearings, injectors, filters and V-belts are all readily available. Do order based on the correct type and, if in doubt, the engine number.

Is the S3L/S4L a direct or indirect injection engine?

It is an indirect-injection engine with a swirl chamber. As a result, it runs smoothly and relatively quietly, but it needs good glow plugs to start easily from cold.