E&MU: EGR Cooling Issues Vex Fleets

Often-Overlooked Component in Exhaust Gas Recirculation Systems Can Cause Big Problem

By Jonathan S. Reiskin, Associate News Editor

This story appears in the July/August 2012 issue of Equipment & Maintenance Update, a supplement to the July 9 print edition of Transport Topics. Click here to subscribe today.

The coolers at the heart of exhaust gas recirculation systems that have been present on diesel truck engines since 2002 have been failing at a worrisome rate, according to several fleet managers.

Specifically, they said, EGR coolers have been cracking and spilling coolant, but the fleet managers credited truck and engine manufacturers for working hard to correct the problems. For their part, engine makers concede that making a durable cooler is problematic, but also said the products have been redesigned and are now doing better.

The cooler troubles also show the importance of bringing mechanical failures to the attention of truck and engine makers promptly, of being persistent and of comparison shopping among all competitors, the maintenance executives said.

“With 2007 and 2010 engines, it’s usually one of the first things that pop up. It’s a very common problem,” said Darry Stuart, an independent maintenance executive who works with fleets on a short-term basis.

“The real issue is that they’re not stout enough, not heavy-duty enough. I don’t understand how it is we can put a man on the moon, but we can’t get an EGR cooler to last,” said Stuart, a former chairman of the Technology & Maintenance Council of American Trucking Associations.

“They happen all the time. It’s an ongoing problem,” said David Foster, vice president of fleet services for Southeastern Freight Lines, Lexington, S.C., of EGR cooler issues.

Another former TMC chairman, Foster said his less-than-truckload carrier watches coolant levels scrupulously, uses oil analysis and checks oil filters for plugging as tactics to keep cooler leaks from causing greater problems.

Reducing the emission of nitrogen oxide compounds, NOx, was a major focus of the Environmental Protection Agency in regulations aimed at truck engine makers from 2002 to 2010. A key development in that process was the introduction of EGR systems to trucks. EGR systems are designed to recirculate exhaust gases through the engine’s combustion chamber, which reduces the amount of oxygen in the air/fuel mixture and lowers combustion temperatures. While EGR has led to a 95% reduction in NOx emissions by trucks over that time, the less vigorous combustion has also reduced fuel mileage.

The EGR cooler is an integral part of the engine, often bolted to the block. It is not like a filter or brake, a part that gets changed regularly. The coolers work like radiators, using regular engine coolant and lowering the temperature of exhaust gas from between 800 to 1,000 degrees Fahrenheit at entry down to 300 degrees before pumping the gas back into the cylinder heads. The process retards the degree to which combustion produces NOx.

Daimler Trucks North America, Portland, Ore., usually powers its Freightliner and Western Star Trucks with engines made in-house by its Detroit unit, formerly Detroit Diesel Corp. Brad Williamson, a DTNA engine manager, said the company’s main Series 60 engine went through three generations of electronic controls from 2002 through 2009.

In 2010, Detroit unveiled a new platform, the DD series, which has yet another round of controls.

“We improved the design to eliminate the inlet and outlet leaks,” Williamson said of the first change that took place in 2004. “For the Series 60, the EGR cooler and related hardware changed significantly and issues with this cooler were greatly reduced.”

Tango Transport, a Shreveport, La., truckload carrier, has a broad collection of experiences with EGR coolers, said Kenneth Eggen, vice president of fleet maintenance. Tango has about 950 trucks, and Eggen said he has gone through three brands of engines.

Brand A — he did not want to use the specific name — failed early and the manufacturer did little to support him.

“We no longer have any of those engines. We got rid of them through our trade cycle,” Eggen said.

Brand B also had a string of early failures, but Eggen said the manufacturer has worked diligently to address the problem. Eggen said Tango continues to buy from Brand B.

Brand C has been the happiest experience because “they work well,” Eggen said of the EGR coolers on those engines.

Eggen said Tango is in the middle of a massive replacement campaign on 450 truck engines. The EGR coolers started failing early, after 30,000 to 150,000 miles driven.

“Now we’re changing them all proactively,” he said.

Few car owners would blink at the notion of a major repair after 30,000 to 150,000 miles, but heavy-duty trucks are very different. Manufacturers boast of B50 engine lives of 1 million miles, meaning 50% of that group of engines made it to 1 million miles driven before failing.

SEFL’s Foster said he did not see many problems in the first generation of EGR engines.

“We didn’t see many big problems until 2007. Those engines had higher EGR usage. There were some problems early on, but not like the magnitude we saw later.”

For Southeastern’s trucks, Foster estimated a B50 life for the EGR coolers of 200,000 to 250,000 miles.

“250,000 miles is horrible. We’re talking a fairly major repair here. Why should that happen at 250,000 miles?” he asked. Foster, the chairman of TMC’s engine study group, said he thinks coolers should last as long as the rest of the engine.

Tango’s Eggen said he would be pretty happy with a lifespan of 500,000 miles for EGR coolers, as that would be a significant improvement over what he has often seen.

EGR coolers have no moving parts. They are vessels that allow gases and liquids to flow through them. That might seem like the basis of a cushy life for a component, but there is more to the stresses they face.

“It’s a harsh environment,” said Jim Schreiber, a customer support manager for Cummins Inc., Columbus, Ind. “The main issue is thermal stress from exhaust gas.”

Schreiber said EGR coolers face two challenges from heat, the absolute level and the gradient. If a truck has been standing still and turned off, the engine’s temperature is the same as the ambient air.

From there it rises quickly to about 900 degrees for exhaust entry, and liquid coolant works quickly to reduce the gas temperature to 300 degrees. That means one end of the EGR cooler is 600 degrees cooler than the other end, and that wreaks havoc with the cooler’s stainless steel body because metal expands and contracts with heat.

“This creates metal fatigue from thermal stress,” Schreiber said. He said that Cummins, the largest supplier of North American heavy-duty truck engines, has learned a lot over the past 10 years through computers simulations and analysis of part life.

As a result, cooler design and production methods have been modified, usually as “tweaks” rather than radical overhauls, said Lou Wenzler, a Cummins sales support director.

The parts expand and contract at different rates, Wenzler said, so Cummins has had to alter part thickness and shape at very small levels to improve reliability.

A field technician in Denver said he has not seen a lot of EGR cooler problems recently on the trucks he services due to cooler redesigns.

“There used to be quite a few problems with them. They weren’t robust enough then,” said Jerry Sheridan, who works for Stewart & Stevenson, a part of the WheelTime Network of truck maintenance shops.

Sheridan said he mainly works on Detroits, and that since a 2007 redesign he has not had too many problems with them. Valves and sensors are more common EGR problems now, he said.

“Originally, the cooler was a small square, maybe 2 feet long, but now it’s really long, about 3 feet,” said Sheridan, adding that the major material in them is coated aluminum.

Sheridan said he inspects the coolers thoroughly at about 300,000 and 500,000 miles. At those inspections, they often go to a radiator shop for cleaning, Sheridan said.

At 800,000 miles, he ships them back to Detroit for remanufacturing.

Manufacturing and maintenance executives also offered tips for longer cooler life.

“There is no preventative maintenance for the EGR cooler per se,” said David McKenna, director of powertrain sales and marketing for Mack Trucks, Greensboro, N.C. “However, there are some routine procedures that should be followed during regular exhaust system inspections.”

“A large majority of EGR cooler performance issues can be traced to plugged [diesel particulate filter] delta-pressure sensor tubes. These tubes can fill with soot, carbon, moisture or some other type of contaminant that can then misinform the system software of current operating conditions,” McKenna said.

“This can contribute to some very premature EGR cooler plugging, and in some worst-case scenarios, cracking. Mack would recommend a twice-annual in-spection of the actual delta-pressure sensor, tubing and rubber connections to prevent any premature cooler problems,” McKenna said.

“The best way to ensure the durability and performance of MaxxForce EGR system components, including EGR coolers, is to follow the maintenance program in the engine operator’s manual and to ensure that engines are programmed with the most up-to-date calibrations,” said Tim Shick, vice president of North American engine sales for Navistar Inc., Lisle, Ill.

Sheridan of S&S also recommended checking for soot, saying that on all engines made since 2007 — meaning with DPF filters — if there’s soot on the tailpipe, then something is wrong.

Schreiber and Wenzler of Cummins warned about air bubbles that can arise when filling a radiator with coolant. Coolant is a much better heat sink than air, so it is important, they said, to get out as much air as possible or hot spots can occur.

Southeastern’s Foster said chemistry can be important.

“If there’s an internal coolant leak, coolant can get into the oil, and everything always finds its way to the bottom of the oil pan,” he said.

Foster said coolant in the oil shows up by leaving traces of potassium and sodium in the oil analysis. As the coolant-tainted oil circulates, it can leave deposits in the filter, thereby clogging them.

Foster and Tango’s Eggen agreed separately that it is important to check engine gauges and fault codes about low coolant or over-heating. They said these clues should be taken seriously and investigated quickly.

Asked about cleaning an EGR cooler, Foster said he has found it difficult to get to that point.

“We haven’t had to clean one, they just fail,” he said.

Although the lack of durability in coolers annoys him, Foster did not ascribe bad faith to original equipment manufacturers.

“I think the OEMs are working hard to address this, but the regulations they had to meet are pretty strenuous. They are used to building robust components, but I think they had too much thrown on their plates at one time. This is just another item of something EPA failed to consider in its estimates of operating costs,” he said.

Stuart said to fight.

“Fight for a better product,” he advised. “There’s always a fight. Things don’t get better if you don’t.”

That being said, he agreed with Foster about not accusing engine makers of malice or incompetence.

“Engines today are very sophisticated and costly. They have amazing technology, but at the same time, the B50 life you see on some parts are not fair to the industry.”

Eggen said he has listened to discussions about EGR coolers at maintenance meetings, and he has heard engine makers place the problem with cooler manufacturers. But, he said, cooler manufacturers respond that they’re just building to the engine makers’ specifications — and that’s why it is important to talk to truck and engine makers.

“We work with manufacturers and hope to eliminate the worst problems, like roadside breakdowns, but you always have to look at other options. All of these manufacturers have issues, but if they can support you, that’s what’s important. We’re ultimately dependent upon the manufacturers,” he said.