Category: Blog – Ask the Diesel Engine Experts

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Top 5 Common Yanmar Engine Problems (and How to Prevent Them)

Yanmar engines have earned a reputation for reliability in marine, agricultural, construction, and industrial applications. Many Yanmar engines provide thousands of hours of dependable service when maintained properly.

However, no diesel engine is immune to wear, contamination, heat, or neglected maintenance.

The good news is that many of the most common Yanmar engine failures are preventable. Understanding the warning signs early can help reduce downtime, avoid expensive repairs, and extend engine life.

Let’s look at five of the most common problems seen in Yanmar diesel engines.

Quick Takeaway: Most common Yanmar engine failures involve fuel delivery, cooling system performance, exhaust restrictions, injector wear, or compression loss. Many of these problems can be prevented through routine maintenance and early diagnosis.
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Diesel Fuel Grades Explained: #1 vs #2 vs #4 (What You Should Actually Be Running)

Not all diesel fuel is the same.

Most people think diesel is just diesel – but in reality, there are different fuel grades, and each one behaves differently inside your engine.

The three main types you’ll hear about are:

  • #1 Diesel
  • #2 Diesel
  • #4 Diesel

Understanding the difference matters: because the wrong fuel choice can lead to poor performance, fuel system issues, or even downtime in extreme conditions.

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Why Most Heavy-Duty Diesel Trucks Use Inline-6 Diesel Engines

If you look at almost any modern long-haul truck in the United States, you’ll find one thing in common:

👉 An inline-6 diesel engine under the hood.

That’s not a coincidence.

It comes down to balance, torque delivery, efficiency, and long-term durability – all critical factors for moving heavy loads over long distances.

Continue reading Why Most Heavy-Duty Diesel Trucks Use Inline-6 Diesel Engines
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Choosing the Right Diesel Engine Common Rail Fuel Injectors

The common rail fuel injector system is a relatively new development in diesel engines, but it brings with it quite a few advantages. With a quality common rail system, you’ll see quieter performance, improved fuel economy, higher torque, and lower emissions. 

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Highway & Heavy Parts Answers Your Diesel Engine Questions: Fuel Systems

Recently, at Highway & Heavy Parts, we’ve expanded our product offering to our customers. We now offer more fuel system components for all major OEMs.

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Why Clean Oil Matters More Than You Think (And How It Protects Your Diesel Engine)

If you’ve already invested in diesel engine parts, you already understand how critical performance and reliability are.

But there’s one system that impacts everything else, and it’s often overlooked:

Your lubrication system.

Clean oil is not just about maintenance. It directly affects how long your components last and how efficiently your engine operates.

Continue reading Why Clean Oil Matters More Than You Think (And How It Protects Your Diesel Engine)
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Diesel Engine Common Rail Injection Explained

We’ve talked a lot about issues you might experience with your diesel engine common rail injectors. But it’s not all about the problems! You also get  a lot of benefits for having this kind of fuel injection system in your diesel engine.

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What to Know Before Buying Connecting Rod Bearings

Connecting rod bearings are one of the smallest components inside a diesel engine, but they play a massive role in long-term engine reliability.

Improper bearing selection, incorrect oil clearance, installation mistakes, or inaccurate measurements can quickly lead to oil pressure loss, crankshaft damage, metal contamination, bearing failure, and catastrophic engine damage.

That is why connecting rod bearing selection should never involve guesswork.

Proper bearing fitment depends heavily on crankshaft journal measurements, housing bore condition, oil clearance verification, engine application, and the condition of the surrounding rotating assembly components.

Quick Takeaway:
Connecting rod bearings must match the exact crankshaft journal size, oil clearance requirements, and engine application. Assuming “standard” always fits can lead to serious engine damage.
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Black Series Lab Episode 1: Why Your Cylinder Liners Are Never Actually Round

Most diesel technicians assume a brand-new cylinder liner comes out of the box perfectly round and ready to install.

However, advanced dimensional analysis shows that even new production liners contain small amounts of geometric variation throughout the liner surface.

While these variations are often microscopic, they can still influence:

  • ring sealing,
  • oil control,
  • blow-by behavior,
  • and long-term rebuild reliability under operating conditions.

That is exactly what Highway and Heavy Parts explores in Black Series Lab– Episode 1. In this episode, we examine:

  • cylinder liner roundness,
  • dimensional stability,
  • storage conditions,
  • advanced measurement technology,
  • and why standard inspection methods may not always reveal the full picture during a diesel engine rebuild.
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Black Series Lab Episode 3: Crosshatch — The Surface You’ve Never Actually Seen

Most engine rebuild conversations focus on the parts everyone can see.

Pistons. Rings. Bearings. Cylinder heads. Gaskets. Liners.

But one of the most important surfaces in the entire engine is almost invisible once the rebuild is complete.

The cylinder liner crosshatch.

That microscopic pattern machined into the cylinder wall plays a major role in oil retention, piston ring seating, compression control, blow-by prevention, and long-term engine durability.

In Black Series Lab Episode 3, we look closer at that surface and explain why the liner wall is not just a smooth bore. It is an engineered sealing surface.

Quick Takeaway: Crosshatch is not just a machining mark. It is a controlled surface pattern designed to retain oil, support ring seating, and help the engine maintain compression and oil control after a rebuild.
Continue reading Black Series Lab Episode 3: Crosshatch — The Surface You’ve Never Actually Seen