The diesel engine may be one of the most, if not the most, complex system on a truck. In order to function as it was designed to, its many components must work in conjunction.
Although some engine components are more complicated than others, each has a vital role in proper engine performance.
Some of the major parts of a diesel engine include the crankshaft, cylinder block, rods, pistons and liners. “These components make up the short block,” said Zack Ellison, director of customer technical support, Cummins Inc. “The cylinder head, which normally is a large casting, bolts to the top of this block and seals in the top of the cylinder.”
Look inside the engine and you’ll find components such as the camshafts and roller followers, which open and close the valves.
On the outside of the engine there are a couple key components including the fuel pump, the fuel injectors and the turbocharger, which is more important today than ever before in order to achieve proper engine performance and power, Ellison explained.
Thomas Miles, marketing manager, North American Aftermarket, BorgWarner Turbo Systems, said that turbochargers have been an important component of the internal combustion engine for many years, starting with their use on diesel engines on WWII bombers.
“The turbocharger’s primary function was for normalization of the engine at high altitudes, and currently, the turbocharger is an integral part of the emissions reduction and fuel conservation objectives set before engine manufacturers,” he said.
“These new emissions and fuel reduction requirements have created new demands on the modern turbocharger manufacturer. The challenges are for smaller, more durable boosting devices that can provide a sufficient mass of air to the engine at all operating points,” Miles explained.
“A direct result of the requirement is regulated two-stage turbos with variable turbine geometry, that contain temperature-resistant alloys and sophisticated boost control devices,” he added.
Although the aforementioned parts are the major components of a diesel engine, smaller parts, like water pumps, oil pans, oil pumps, rod bearings, main bearings, oil filters and oil coolers, also are parts of the engine.
“My company has design standards for each one of those components, as do most other companies, that regulate how strong these parts need to be and how long they should last,” Ellison said.
“In most cases, major parts like the crankshaft, connecting rods, cylinder block and cylinder head should live way beyond the first overhaul, meaning thousands of hours. I’ve talked to some customers who have more than a million miles on their trucks and haven’t had to do anything to their engines,” he said.
“I’ve talked to equipment operators who have as many as 25,000 to 30,000 hours of operation on their equipment, and in those time periods, you would not expect one of the major engine components to break,” Ellison said.
“The engine components are designed for what I would classify as infinite life. It doesn’t mean that they won’t wear out; you will have to replace cylinder heads, for example, but that will be at the time of an engine overhaul,” he explained.
Although eventually parts do wear, they can last longer by working together to help the engine function to the best of its ability.
“A diesel engine’s performance depends on the effectiveness of the integration of all these different systems,” Ellison said. “A total system integration is important-the parts together don’t do very much unless they fit the job that needs to be done while meeting the emissions requirements.”
For example, the amount of fuel that is delivered during each power stroke must match the amount of air that is available for that power stroke. “The fuel system and the turbocharger system must be balanced so that you get the right amounts of fuel for the rpm and the power requirements that the engine is being asked to do,” he said.
“It is important that everything matches up precisely, otherwise you get into situations where the engine doesn’t perform well.”
Although diesel engines are built to last, they do experience problems and have some components that require periodic maintenance. Ellison said that a component like a fuel injector may need to be replaced after 700,000 or 800,000 miles.
“Its life depends very heavily on the quality of the fuel used and how often the fuel filter is changed. A component like the water pump normally has to be replaced before an overhaul, and if the turbocharger needs to be replaced, it is because the air system has not been maintained as well as it should have been,” Ellison explained.
You should pay close attention to the air system and air cleaner maintenance to avoid premature failure. If an air cleaner is installed incorrectly, dust, dirt and debris can travel into the engine, which could cause the rings and liners to wear prematurely, or may result in turbocharger failure.
“You also should make sure that the cooling system is treated with corrosion inhibitors or long-life coolant. Cooling system problems can lead to corrosion, liner cavitation and freezing in cold weather. Pay attention to the oil change interval, the oil filtration and the quality of oil and oil filters-they will go a long way,” Ellison said.
Your customer should be educated on the type of oil he uses in his vehicle. In order for the engine to do its job efficiently, the proper oil is key. Without adequate lubrication, your customer’s engine may wear prematurely.
Colleen Flanagan, category manager, Commercial Transportation Lubricants, Petro-Canada Lubricants, discussed the importance of lubrication as it pertains to each component within a diesel engine.
“A modern engine oil has been carefully developed by engineers and chemists to perform several important functions. The efficient operation of an engine depends on the oil doing the following things,” she said.
- Permitting easy starting,
- Lubricating engine parts and preventing wear,
- Reducing friction,
- Protecting against both rust and corrosion,
- Keeping engine parts clean,
- Reducing combustion chamber deposits,
- Fighting soot,
- Cooling engine parts,
- Sealing in the combustion pressures, and
- Be non-foaming
Flanagan explained that the ease of starting an engine depends not only on the condition of the battery, ignition and fuel quality, but also on the flow properties of the motor oil.
“If the oil is too viscous or heavy at starting temperatures, it will impose enough drag on the moving parts that the engine cannot be cranked fast enough to start promptly and keep running,” she said.
Since cold temperatures thicken all oils, an oil for winter use must be thin enough to permit adequate cranking speeds at the lowest anticipated temperature, and it also must be fluid enough to flow to the bearings quickly to prevent wear, she explained. “In addition, the oil must be thick enough to provide adequate protection when the engine reaches normal operating temperatures.”
Flanagan went on to explain that the characteristic of an oil which determines ease of cranking is its viscosity at the cranking temperature. Viscosity is a measure of the oil’s resistance to flow, and “this resistance, or fluid friction, keeps the oil from being squeezed out from between engine surfaces when they are moving under load or pressure,” she said.
“Resistance to motion or flow is a function of the molecular structure of the oil, and since this resistance is responsible for most of the drag put on the starter during cranking, it is important to use an oil with viscosity characteristics that ensure satisfactory cranking, proper oil circulation and high temperature protection,” Flanagan explained.
Once your customer starts the engine, the oil must circulate promptly and lubricate all moving surfaces to prevent the metal-to-metal contact that would result in wear, scoring or seizure of engine parts.
Oil films on bearings and cylinder walls are sensitive to movement, pressure and oil supply, so they must be replenished continually by adequate flow and proper oil distribution, she explained.
Once the oil reaches the moving parts, its function is to lubricate and prevent the possibility of wear of the moving surfaces. Lubrication engineers call this full-film, or hydrodynamic lubrication, which occurs when the moving surfaces are separated continuously by a film of oil, Flanagan said.
“The determining factor in keeping these parts separated is the viscosity of the oil at its operating temperature, which must remain high enough to prevent metal-to-metal contact. Since the metals do not make contact in full-film lubrication, wear is negligible unless the separated parts are scratched by particles thicker than the oil film itself,” she said.
Crankshaft bearings, on the other hand, as well as connecting rods, camshaft and piston pins, normally operate with full-film lubrication.
Under some conditions, it is impossible to maintain a continuous oil film between moving parts and there is intermittent metal-to-metal contact between the high spots on sliding surfaces, which is known as boundary lubrication, Flanagan said.
“Under these circumstances, the load is supported only partially by the oil film, and the oil film is ruptured, resulting in significant metal-to-metal contact.
“When this occurs, the friction generated between the surfaces can produce enough heat to cause one or both of the metals in contact to melt and weld together. Unless counteracted by proper additive treatment, the result is either immediate seizure or the tearing apart and roughening of the surfaces,” she explained.
In addition to having adequate lubrication for optimal engine operation, Ellison added how important it is that the engine is matched up with the application and performance that is required for that particular piece of equipment. “For example, you wouldn’t use an off-highway construction engine in an on-highway tractor-trailer,” he said.
“In most cases, diesel engines today have turbochargers that eliminate the majority of smoke. They supply enough air for all of the fuel to burn with the Tier 1, Tier 2 and Tier 3 emissions requirements for the off-highway engines and to adhere to the EPA-emissions requirements for ’02 engines and now the ’07 engines,” he explained.
The smoke almost has been eliminated in the older engines and it has been eliminated completely with the ’07 on-highway engines.
“Oil companies have done a very good job developing new additive packages that have kept up with emissions changes,” Ellison said. “Oil today is far superior to any oil we had 10 or 12 years ago.”
He added that it’s also important to operate the engine within the power band and the rpm range in which it was designed to operate. “If your customer has an engine that has a maximum speed rating of 2100 rpms, he shouldn’t travel down a hill and push it up to 2400 rpms or 2500 rpms.”
Ellison explained that electronics have had an impact on engines. They have helped to clean up the emissions, given variable timing and fueling of the engine and have given much more freedom of design with the combustion process than a mechanical fuel system or mechanical engine would have given, he said.
Electronics help your customer run his engine more efficiently and allow the truck to gear fast and run slow. They have provided better troubleshooting capability so when there is a problem with the engine, the engine control module will register a fault code that points the technician to the component that needs to be replaced.
“This technology makes service on the product easier and improves emissions and fuel economy,” Ellison said. “Without electronics, we would not have the engines that provide the fuel economy and the clean emissions that we have today.”
Proper operation is important to get long life out of the engine. “If you keep the proper fuel in it, use the oil that the engine manufacturer recommends, perform the appropriate maintenance and routinely check things like the oil filters and air cleaners, diesel engines will last an amazingly long time,” Ellison said.
“If there is any type of failure, I would qualify it as a soft failure, meaning an external part that could be changed readily and easily,” he added. “Engines just don’t break like they did 15 or 20 years ago-they are much more reliable.”
Service Secret
Heavy-duty vehicles operate in a number of different environments whether it be over the road, in a city or in a vocational application. The diesel engine will be affected by the environment in which the vehicle operates.
According to the Technology & Maintenance Council (TMC), frequent starts and stops, as experienced in city driving, demand top quality lubricant that helps the engine last.
Engine operation at low rpm with no load, particularly in vehicles traveling in cold weather, can be a major cause of oil dilution resulting from unburned fuel passing beyond the piston rings, according to TMC.
When a diesel engine operates under varying load factors through its duty cycle, it may put too much demand on the engine cooling and lubrication system, which eventually may result in excessive temperatures and possible oil deterioration, TMC explained.
Steady engine operation will result in normal operating temperatures which provide maximum oil life. High horsepower demand tends to raise the engine temperature above normal, and high operating temperatures will shorten oil life expectancy, according to TMC.
Tech Tip
Temperature can have an impact on the engine’s ability to do its job. It also can affect the oil’s viscosity, which is a measure of the oil’s resistance to flow. Colleen Flanagan, category manager, Commercial Transportation Lubricants, Petro-Canada Lubricants, said that the effect of temperature on viscosity varies widely with different types of oil.
“A standard has been developed for measuring the amount of viscosity change with temperature change. This standard is called the Viscosity Index (VI). An oil with a high VI is one that shows less change in viscosity over a wide range of temperatures,” she explained.
“Today, through the use of new refining methods and special chemical additives, there are many high VI engine oils that are light enough for easy cranking at low temperatures and still are heavy enough to perform satisfactorily at high temperatures. These oils with high VIs are known as multi-grade oils,” Flanagan said.
These multi-grade oils are able to perform well in both the winter and the summer, and are recommended by most vehicle and engine manufacturers.
The Right Facility
Zack Ellison, director of customer technical support, Cummins Inc., said that it’s important for a customer who is getting ready to buy a piece of equipment with diesel power to understand the capabilities of his selected repair location.
He should ask himself how closely the facility is located to where he operates his equipment, so that should there be any problem, he knows whether or not the repair location will dispatch a field truck and technician to repair that problem.
“After the unit is sold, it’s very important that any time your customer has a problem, he can get good, high quality service for his engine,” Ellison said. “We require our distributors, branches and dealers to go through rigorous training and also to stock the necessary diesel engine parts.”
The ideal facility starts with the right parts and training. It then is up to that facility to earn its customers’ loyalty by providing quality service. Your customers may feel that choosing a repair location may be just as important as choosing the right engine.
Who To Contact
For more information on diesel engines or engine parts, you may contact the following companies directly, or use the FREE Reader Service Card in this issue. Other companies offering information on engines can be found in the Truck Parts & Service Aftermarket Buyers’ Guide & Directory as well as in Buyers’ Guide section on our web site at www.truckpartsandservice.com.
Alliant Power
Sun Prairie, WI
866-283-1785
www.alliantpower.com
BorgWarner Turbo Systems
Arden, NC
828-684-4148
www.turbos.bwauto.com
Caterpillar Inc.
Mossville, IL
309-675-1000
www.cattruckengines.com
Clevite Engine Parts
Ann Arbor, MI
800-338-8786
www.engineparts.com
Cummins Inc.
Columbus, IN
800-343-7357
www.cummins.com
Detroit Diesel Corp.
Detroit, MI
313-592-5000
www.detroitdiesel.com
Esco Industries Inc.
Corona, CA
951-371-2177
www.escousa.com
Federal-Mogul Corp.
Southfield, MI
248-354-7700
www.federal-mogul.com
International Truck
And Engine Corp.
Warrenville, IL
630-753-5000
www.internationaldelivers.com
Interstate-McBee
Cleveland, OH
800-321-4234
www.interstate-mcbee.com
IPD Inc.
Torrance, CA
310-530-1900
www.ipdparts.com
Mack Trucks, Inc.
Allentown, PA
610-709-3011
www.macktrucks.com
Petro-Canada Lubricants
Chicago, IL
888-284-4572
www.petro-canadaamerica.com
Volvo Trucks
North America, Inc.
Greensboro, NC
336-393-4200
www.volvo.com
