The labels show principal elements of V-Pulse EGR system on Volvo's VED12. None require any special maintenance, the builder says.
October is here and the sky hasn't fallen, even though diesels with exhaust-gas recirculation (EGR) are now coming off assembly lines. EGR adds complexity and cost to a new truck, but engine builders have established no maintenance requirements for the special apparatus. Their advice: Pay close attention to oil changes and the cooling system maintenance.
EGR sends varying amounts of cooled exhaust gas back to the cylinders to displace oxygen, which lowers combustion temperatures and reduces smog-forming NOx. EGR gear includes special valves, a water-to-gas cooler, and in some cases a variable-geometry turbocharger.
A few of the most recent diesels were designed with EGR in mind. But older models needed redesigned pistons and new fire rings to contain soot and acids that can seep into crankcases. What gets through will be dealt with by new CI-4 motor oil formulated especially for EGR'd diesels.
Engine makers say EGR components will last indefinitely. None has scheduled any special maintenance, and all note that the systems are monitored by the engines' electronic control modules. Drivers will be alerted via warning lights to any malfunctions; these will also be logged in the ECMs' memories as fault codes.
Cummins says the same types of valves, coolers and VG turbos have been running in Europe for several years, albeit in smaller light-duty diesels. Parts in its commercial truck diesels are extra stout, with EGR valves lubed for life and the coolers made of stainless steel, says Tom Kieffer, executive director for marketing.
Coolers have large passages, ½ inch wide by ¼ inch tall, so exhaust particles will not stick and create hot spots. Engine coolant passes through the cooler, carrying away heat from the recirculated exhaust gasses. Truck builders have enlarged radiators and enhanced the flow of air under the hood so this extra heat can be shrugged off.
Highway tractors with EGR'd Cummins diesels have accumulated more than 6.4 million miles, Kieffer says. The highest mileage achieved by any one engine is now over 200,000, which is not high by over-the-road standards.
Volvo has 24 test vehicles running with its V-Pulse system, says Jim Fancher, marketing manager for power trains. Three are in vocational trucks. V-Pulse consists of two poppet-type valves, a reed-type anti-backflow valve and a water-to-gas cooler; they need no special maintenance.
The cooler features a turbulator that spins the coolant and gases to agitate them so any contaminants remain suspended; thus the cooler is self-cleaning, Fancher says. V-Pulse uses a standard turbocharger instead of the more complex variable geometry type.
Detroit Diesel in the last two years has built 2,500 EGR'd diesels for city transit buses throughout North America. These are 8.5-liter Series 50s, which are essentially four-cylinder versions of the six-cylinder, 12.7-liter Series 60. Transit bus experience may be a good indicator of how cooled EGR will work for owners of construction trucks, which, like buses, stop, start and idle a lot (see caption above).
Series 60s have the same type of EGR system. Along with internal redesigns, engineers also cut about 25 pounds out of the S60. That's about what the EGR gear weighs, so the S60 remains the lightest big-bore diesel available, says Chuck Blake, a staff applications engineer.
Keep things clean
Although EGR parts themselves should need little or no attention, basic maintenance becomes more important. "Before, we would lay out the schedules and say, you should do maintenance,'" says Fancher at Volvo. "Now, you must do the maintenance. Before it might have been okay to cheat a little on oil changes, but now it's not."
Mark Wildman, manager of field service for International Engine, agrees. "The big thing is maintenance—clean air, clean fuel and clean oil," he says. Oil and filter changes must be done on schedule, and only good, properly managed fuel delivered to the engine. If you do not now use a fuel filter/water separator, you should be sure it's included on any new chassis you buy. Air filters should be changed on schedule, or as indicated by a monitoring gauge.
Oil change intervals must not go beyond recommendations, but in most cases the intervals have not been shortened, thanks in part to the new CI-4 motor oil. But if extended drain intervals are attempted, they must be accompanied by regular oil analysis.
"Keep the level of the coolant up, because the EGR cooler is rather high in the cooling system and doesn't like low coolant levels," Wildman says of International's VT-365, but it's also true of other EGR'd diesels. "Air bubbles can form, which would be hard on the [EGR] cooler, and of course other things in the system."
At times, the cooling systems will run 10 to 30 degrees hotter, so the additive package in the cooling system must be kept up to spec so the coolant stays strong. Be sure clamps and hoses are healthy, and replace them at the first sign of weakness in metal or rubber.
Keep all heat exchangers clean and free of bugs and dirt, Fancher advises. The bug screen should be frequently pressure-washed, and the radiator and aftercooler washed as needed, especially in construction trucks, which can pick up dirt and debris on work sites.