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Truck cooling systems

Today’s cooling systems are more than up to the task of handling the much higher levels of heat generated by emissions compliant diesels.


A major design issue, and a challenge for some fleets with 2007 emissions compliant diesels, was the much higher levels of heat generated by those engines. By 2010, however, cooling systems on truck powerplants were evidently more than up to the task.

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In most cases, cooling systems on 2010 engines are unchanged from their 2007 predecessors. “From a design perspective there haven’t been any changes in cooling systems between Cummins’ 2007 and 2010 emissions compliant engines,” says Tracy Kiser, on-highway communications manager. Likewise, according to Kenworth Truck Co., no major changes were required to cooling system design for 2010 engines.

Part of the explanation for that nearly universal answer can be found in the emissions control solutions employed by manufacturers to meet 2010 requirements. “We did not need to change anything within the cooling circuit to meet the U.S. EPA 2010 regulations,” explains David McKenna, Mack Trucks director of cumminspowertrain sales and marketing. “The SCR system allows us to significantly reduce the recycled exhaust gas flow rate. Allowing more oxygen in-cylinder means a more efficient and complete combustion process and less rejected heat, which is also wasted energy.” 

“2010 engines are more efficient than 2007 models due to the new regeneration technology, which uses less exhaust gas regeneration (EGR),” says Ed Saxman, product manager—powertrain at Volvo Trucks North America. “The improved efficiency means there is less heat being put into the cooling system than before, so there have been no changes to the radiator or cooling system. 2010 cooling systems have even more margin than before to meet the most strenuous challenges without overheating.”

Henry Krautner, manager of on-highway application engineering at Detroit Diesel Corp., notes that heat rejection from engines has detroit dieselactually decreased with the launch of 2010 models employing SCR technology. “Therefore,” he adds, “cooling systems in 2010 engines could actually be reduced slightly in size compared to their 2007 predecessors. However, this trend toward lower heat rejection for 2010 only applies to engines using SCR to meet emissions requirements.”

For its Paccar engines, Andy Hoffman, Peterbilt field service manager, says that only minor changes were in cooling systems for 2010. “The two main changes were cooling lines that were added to cool the SCR components and the fan insertion was changed on cooling modules for improved air flow,” he relates. “The coolant lines added to cool the injector and heat the DEF when necessary could add up to a gallon of fluid to the system depending on the setup and length of the lines.”
At Navistar, where EGR is employed to meet diesel engine emission standards, cooling systems for 2010 engines were upgraded. “A key area of improvement was substitution of an air-to-air aftercooler in place of the coolant-to-air unit on 2007-09 engines,” explains Kirby Chapman, director, thermal management systems. “The air-to-air cooler provides cooling capability, which is a vital part of our approach to meeting emissions standards. The low temperature radiator that cools the twin-series turbocharger inter-stage cooler and the EGR cooler was redesigned as a three-pass unit, upgraded from the previous single-pass design, improving cooling capability. The design and arrangement of heat exchangers in the 2010 EGR cooling module also assures that the engines run cool.”

Fan drive technology
Today’s highly advanced cooling systems for on-highway tractors include fan drive systems that are optimized to better manage airflow, help boost fuel economy by using less horsepower, and to reduce noise. Most OEMs today provide complete fan drive and fan systems as a standard package on new vehicles. Fan drive suppliers work closely with vehicle OEMs to develop the most effective and efficient solutions.
Fan drive suppliers include Horton, which offers its line of DM Advantage fan drives designed for high heat applications in on/off and two-speed models. Horton also offers its VMaster viscous air-sensing fan drive and Stratis viscous fan drives. BorgWarner Thermal Systems also offers a variety of fan drives. Among them are the company’s Cool Logic multi-speed fan drives, Kysor on/off fan drives and direct-actuated Visctronic fan drives.

As engine design needs change, manufacturers continue to develop cooling technology that meets the requirements of North American Class 8 engines. While new emission regulations present an ongoing challenge for makers of truck cooling systems, manufacturers continue to meet those challenges.

Cooling system maintenance
While 2010 engines are designed with highly capable cooling systems, the heat that is produced by modern heavy-duty diesels demands that equally effective coolant and coolant filters be used as part of a comprehensive maintenance program. Coolant and coolant filter suppliers have risen to the occasion by developing and refining products that protect engines based on OEM requirements, and provide for long life and reduced maintenance costs.
Coolant filters from suppliers like Wix and Donaldson, among others, help maintain proper engine heat transfer by filtering solid contaminants from the coolant and by minimizing corrosion and deposits in the cooling system. Coolant filters also are used to introduce Supplemental Coolant Additives (SCAs) when required. These corrosion inhibitors dissolve into the coolant, forming a protective film on all metal surfaces in the cooling system. The inhibitor is a combination of chemical compounds blended to provide corrosion and cavitation erosion protection, pH control and water softening.

Engine manufacturers offer fleets support and advice for cooling system maintenance. Extended life coolant is standard on Kenworth trucks, which recommends that coolant and filters be replaced at 120,000 miles or annually.

Volvo Trucks offers a choice of standard low-silicate ethylene glycol base coolant, requiring the periodic maintenance of SCAs, or extended life coolant, which does not require regular coolant SCAs.
Andy Hoffman, Peterbilt field service manager, says that fleets need to know what kind of coolant is being used in their vehicles. “One of the more common cooling issues comes from the mixing of extended life and non-extended life coolants,” he relates. “This mixture will lead to premature failure of the cooling system. With regard to coolant filters, it is important to understand if the vehicle came with a non-chemical filter. Never use filters that contain SCAs in a system that uses an extended life coolant.”

Navistar continues to use Organic Additive Technology (OAT) coolants for factory fill as well as development. In 2010, the OEM introduced a nitrite-free, heavy-duty OAT coolant for improved aluminum protection, oxidation control and elastomer compatibility. “OAT coolants also reduce maintenance by eliminating the midlife requirement to service the cooling system with coolant additives,” says Heather DeBaun, technical specialist, lubricants and coolants.
borg warner
“The key to ensuring that cooling systems are operating as reliably and efficiently as possible is to follow the manufacturer’s maintenance recommendations,” states Cummins’ Kiser. “This includes making sure the system is maintaining proper pressure by using standard cooling system pressure testing tools at regular maintenance intervals. Also, fleets that use conventional coolants need to make sure that supplemental coolant additive levels are being maintained. Fleets using long life coolants should follow the coolant manufacturer’s recommendations. Finally, if abnormal coolant consumption is noticed, it’s important to find the cause and address it.”

Brent Calcut, supervisor, chemical technologies at Detroit Diesel, notes that fleets need to decide which type of coolant they will use and create an appropriate maintenance plan. Conventional coolants need to be checked routinely with a refractometer to ensure they contain enough additive and to measure freeze point, he advises. Donaldson

Also, while extended life coolant does not require routine additive additions, check regularly for dilution.

“Consult your engine, coolant and filter suppliers,” Calcut adds. “Lots of information is available. Get educated, have a plan and stick to it, and you shouldn’t have problems.”

Fleet Equipment Magazine