Mercedes Diesel Engine EGR Cooler Diagnosis

The EGR cooler is one of the most important components on a diesel engine these days since it controls the amount of exhaust that transfers from the exhaust system in to the intake system. Cooled exhaust funneled to the air intake reduces NOx (nitrogen oxide). You would not think raw exhaust would help reduce emissions when the exhaust is the unfiltered by-product of combustion.

Engineers begged to differ and designed an EGR valve to route cooled exhaust to the intake system when needed. In the days of old everything went to the atmosphere which was the easy no hassle way but since man has a conscience and started the EPA (Environmental Protection Agency) the levels of emissions were regulated heavily starting in 2007.

The EGR cooler in the video is a 2006 and being 13 years old has done well considering the volume of exhaust gas flowing through it along with hot coolant circulating around inside to cool the exhaust. However time plus wear and tear has caused the cooler to fail and allow coolant in to the intake which in turn caused white smoke. The cost in Canadian dollars before tax was $1500.00 so spread out over 13 years is not a bad deal.

The emissions are reduced but soot levels increase and contaminate the manifolds, valves and sensors along the way. Raw exhaust is the most contaminated part of combustion and when you consider the effect of this gas going in to the engine intake makes me wonder what were they thinking. This system works to reduce NOx but what happened in 2007 is engine manufacturers decided in order to meet EPA emission requirements diesel engines needed more EGR.

International decided to stick with the higher EGR theory while Cummins designed an add on emission device called SCR (selective catalytic reduction). One extra step was to add DEF (diesel exhaust fluid) to the SCR system in order for it to work. International went with customer feedback not wanting to have to add another fluid to their vehicles. Fleets were probably thinking about the hassle of storing bulk DEF for their trucks and the extra expense and trusted International with their marketing claims that they could meet emissions without adding SCR to their diesel engines.

Forward to the present International has shut down their diesel engine manufacturing due to engine and component failures caused by excessive EGR. Allowing toxic exhaust gases in to the engine intakes took it’s toll and International Corporation suffered greatly from this engineering oversight.