Diesel Enthusiasm Often Tempered By Fear of the Unknown - Engine Builder Magazine
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Diesel Enthusiasm Often Tempered By Fear of the Unknown


Most automotive guys understand the principles of an internal combustion engine. Whether it is gasoline or diesel these are fuel, fire, and compression! Without one of these ingredients, the internal combustion engine will not function.

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So what is it about diesel engine rebuilding that makes automotive guys so nervous? This basically comes down to what all rebuilders and technicians face: the unknown.

What may make some automotive guys nervous is not understanding how these basic principles apply to a diesel engine. For the most part most automotive rebuilders and technicians know WHY the diesel works, they are just not familiar with HOW the diesel works.

Just as with the gasoline engine manufacturers, there are different diesel manufacturers that all tend to make the engine function using the same principles, just in a different way. This really shouldn’t make the automotive guys nervous. Everything is still done to a specification. I often use this as an opportunity to explore the unknown.


One thing diesels can be is intimidating. They are usually big, noisy, spin very low rpm, and everything is heavy. These engines produce major torque and demand high strength parts for longevity.

Diesel engines can often be very costly, as in “if something goes wrong it puts some major pinch on the profit margin.” On average, a diesel engine could cost as much as three times what it takes to build a comparable gasoline engine.

Part of this is due to the cleanup required: diesel engines can be very nasty on the internals. They tend to soot the oil due to blow-by, which takes a little more cleanup. This blow-by comes from different factors such as the compression ratio and the use of turbochargers.


The next time you’re at a stoplight or at a rest area and see an older rig idling, pay attention underneath the truck. You will probably see some smoke. This smoke is made of blow-by gases that are coming out of the “drip tube.” That was the only way the older engines could expel those crankcase vapors since they did not have PCV systems. They were generally rubber hoses that came down from the valve cover and ran down the side of the engine and stopped at the bottom of the oil pan. Understanding this can help explain the price of the rebuild.


Some in-frame rebuilds on fleet vehicles can take approximately 40 hrs. Generally, an in-frame consists of main and rod bearings, pistons, rings, liners, recondition the cylinder head and of course new gaskets. This recondition will cost in the neighborhood of $10,000-$12,000, which may seem a very costly rebuild, but remember: this should last from 800,000 to 1 million miles.

Most automotive shops can perform service on full size diesel pick-ups and minor repair on fleet size trucks with just the equipment they already have.

Heavy duty trucks require a variety of special tools just as an automotive shop requires them – the big difference is that the heavy duty shop will need a lot bigger tools. This comes from the parts being so heavy. These tools also generally come with a much greater price. These tools may include a hoist, brake tools, wrenches and sockets (generally sizes from 1 ½?  to 4?), drain pans, transmission jacks and lifts. All things you already own, you say? Sure, but let’s take a look at the drain pan. Most automotive drain pans will hold up to lets say 10 quarts of oil and cost around $10. A big equipment drain pan will hold approximately 10-12 gallons and cost approximately $100.


The other day I had to buy a new automobile transmission jack for the shop. I paid around $400. If I had to buy another transmission jack for the trucks, I could expect to pay around $2,000.

If you’re considering expanding beyond engine work, remember that with heavy duty trucks will come heavy-duty training. Take, for instance, the brakes on a fleet vehicle. They are controlled by pneumatics and can be very dangerous. Serious injury or death is possible when servicing the brake chambers, especially to an inexperienced technician.

There are also different aspects of the clutch systems which require periodic adjustments which are unlike a car that never needs adjusting. Cars and light trucks don’t really have grease fittings anymore, compared to a fleet vehicle which may have as many as 40-plus grease fittings. Electrical systems are different also. Some brands of heavy duty trucks use the same color wire throughout the vehicle, with each wire encoded with different numbers for tracing. This can be a problem when the numbers start to fade off.


Keep in mind, too, that there are a lot more fluids used in heavy duty diesels compared to automotive vehicles. Typically heavy duty diesels in on the road trucks use the following: 10 gallons of engine oil, 5 gallons of transmission fluid, 5 gallons in each differential, 10 gallons of antifreeze mix in the coolant system, and approximately 5 lbs. of refrigerant in the a/c system.

In today’s economy it may be your best bet to stick with what you know, even as you’re looking to expand into niche markets that interest you. Always learn new things, but concentrate at what you’re good at and enjoy. If you like working on Detroit Diesel then be the best Detroit man in town. You have to have a niche which sets you above the rest. Automotive shops are the same way.


There are still independent garages who can perform repair on a vast array of vehicles, but in today’s economy you see more specialized shops concentrating on certain vehicles. This tends to make them stronger; being on top of their game and doing what they enjoy.

Robert McDonald is owner of Atlantic Engines in Granite Falls, NC, and specializes in high performance diesel and gasoline engines and cylinder heads for street, marine, dirt or drag racing. Bob can be reached at [email protected].

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