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How Navistar solved its EGR problems


kscarbel2
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Truck News / February 5, 2015

It’s no secret that Navistar International had its share of EGR-related failures as it attempted to meet EPA10 emissions standards without the use of SCR exhaust aftertreatment.

The company very candidly addressed the issue at its Analyst Day earlier this week, and offered a full explanation of the fix it has implemented.

Tim Shick, vice-president of sales support with Navistar, said most of the problems could be traced to the turbo air control valve, which connects directly to the engine’s electronic control module (ECM). The ECM, very importantly, would dictate via that connection how much fresh air should be supplied to the engine and for how long, as well as how much hot exhaust should be supplied and for how long, to effectively reduce emissions.

However, constant vibration and wind underneath the hood would cause the connection to become loose.

“When this began to fail, it didn’t become totally dislodged,” Shick explained. “The truck went down the road and the connector moved around due to vibration and wind under the hood and through a process called ‘fretting’ would wear these pins down to the point where it would connect intermittently.”

The intermittent connection would cause the device to “overfuel” the engine with sooty exhaust, which first went to the EGR valve. Exacerbating the situation, the shaft on the EGR valve was prone to failure, allowing in a free-flow of soot-saturated exhaust.

“What usually happens is you get an open flow of exhaust coming in at will, which is full of soot, because the engine is not combusting all the fuel completely and it goes into the EGR coolers,” Shick explained.

Next thing you know, the exhaust manifold, valve and coolers inside the EGR housing are filled with soot. Fuel economy deteriorates, a dashboard light comes on and the truck needs to be taken out of service.

This was problematic with engines produced in 2010 through 2012. However, by 2013 Navistar had identified the problem and taken steps to address it, Shick explained.

For starters, it hardwired the connection from the turbo air control valve to the ECM so that it could no longer shake free and lose its connection as a result of over-the-road vibrations. It also made the EGR valve shaft 30% larger and less susceptible to sticking.

Navistar also removed some sharp edges from within the system that were causing premature fatiguing and cracking of components. It also redesigned the EGR cooler, providing more room for exhaust gases to flow.

Navistar says the improvements have dramatically reduced warranty claims. It now updates used trucks taken in through its Diamond Renewed used truck reconditioning program to implement the improved components. International MaxxForce engines built in 2013 and after will already come with the fix.

An International dealer can determine whether pre-2013 engines have been updated with the improved parts. Navistar is so confident with the fix, it offers a one-year, 100,000-mile warranty on used trucks that have been reconditioned through its Diamond Renewed program.

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