Heading off engine exhaust aftertreatment headaches can be as simple as doing preventive maintenance by the book, representatives of fleets and truck and engine makers said.

Diesel particulate filters (DPFs) and selective catalytic reduction (SCR) systems have helped Class 8 trucks cut emissions of particulate matter, or soot, and nitrogen oxide (NOx) compounds as a result of federal clean-air mandates that took effect in 2007 and 2010. However, fleet maintenance professionals often describe difficulties in keeping these “green” systems and components running.

Gregg Mangione, senior vice president of maintenance at Penske Truck Leasing, said that today, the issues Penske sees with DPFs are mostly the result of “upstream failure” that contaminates the DPF with fuel, oil and coolant. SCR systems are another story as Penske continues to see reliability issues with NOx sensors, diesel exhaust fluid (DEF) dosers and pumps, he added.

Sensor-related problems and those related to wiring harnesses are larger issues than DPFs, Mangione noted, however.

Educating technicians to ­fully diagnose fault codes reduces repeat repairs, Mangione said. Penske uses artificial intelligence to gather information linking repair data to fault codes to help guide a technician to the most likely diagnosis, he said.

The top reasons for maintenance issues include a lack of driver knowledge to recognize a potential problem or procrastination in reporting an ­issue, among others, said Roy Horton, director of product strategy for Mack Trucks. Another is technicians not knowing how to diagnose the root cause of a problem due to the complexity of the system, he said, noting these can then lead to additional expenses from replacing parts as a result of guesswork.

Jack Legler, technical director for the Technology & Maintenance Council, a council of American Trucking Associations, recommends using quality DEF to help bypass troubles with SCR, including some sensor failures because inferior products can damage those vulnerable devices.

Joel Morrow, head of research and development and senior driver at Ploger Transportation, said his fleet heads off DPF problems by discouraging idling, and by gearing their trucks to keep the engine within the peak torque range at cruise. This raises exhaust temperature, and the higher heat helps burn off soot before it builds up.

Ploger treats each tank of fuel with a certain brand of additive that ensures its cetane rating, which is an indicator of how quickly fuel ignites, exceeds factory requirements of 45 for the fleet’s Volvo and Mack tractors.

“Maintenance headaches are created by either not following factory service recommendations or not catching clues to upstream issues when maintaining the system,” said John Moore, product marketing manager for Volvo Trucks North America, noting it comes down to training, knowing the components and how the system works. “Clean the DPF at recommended intervals instead of waiting for a message from the information display.”

Mangione said that Penske created its own DPF cleaning centers, which meet Six Sigma requirements, by using approved procedures several years ago. These centers are where Penske collects data during cleaning, which has enabled the creation of a scheduling program that prevents downtime by cleaning DPFs before problems occur.

Brian Daniels, manager for Detroit powertrain and component product marketing, suggests cleaning the DPF at the normal interval of 300,000 to 400,000 miles and conducting regular inspections of components.

Ultimately, Mark Ulrich, director of customer support at Cummins, advises maintenance shops to follow the manufacturer’s published maintenance recommendations.

“There’s no better recommendation for avoiding trouble,” he said.

BY John Baxter
October 25, 2019
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