Another rebuild not uncommon with the DT MaxxForce. We have found this out in the last couple of years. There is so much exhaust going through the intake system and out the exhaust the second time has caused premature wear beyond belief. Navistar decided to tackle the 2010 emissions requirements set out by the EPA using EGR. They wanted to get as much cooled exhaust through to the intake as possible to reduce NOx (oxides of nitrogen). The more EGR the better but at a huge cost.
imagine the engine burning diesel under extreme heat which is referred to as ‘heat of compression’. If you were wondering diesels ignite by high compression creating the internal heat in the cylinder enough to ignite the injected diesel. There is an actual explosion in the cylinder during the power stroke (if you ever wondered why diesels were so noisy). Also imagine the contamination in the exhaust that gets recirculated back in to the intake to be reused for combustion.
This process was developed by engineers to reduce oxygen and heat in the combustion chamber to cut down on NOx but at the same time creating more soot because of the cooler temperatures. This mixture running through the emission system eventually plugs everything up..everything in it’s path. The concept works but only when the system is working properly. I heard a story regarding the reason why Navistar did not want to pursue SCR (selective catalytic reduction) like Cummins and it would have made total sense to me back then.
If I was a fleet operator and a sales guy came in and started pitching a new emission system that was state of the art (a lot of them say that) controlling emissions much better than the older EGR system. But…there would be extra components added on which would add GVW to the vehicle and these new components would not work without adding another special fluid called DEF (diesel exhaust fluid).
Along comes Navistar who are sticking to straight EGR who said their engines are going to meet emissions and you don’t have to bother storing hundreds of gallons of DEF on site and you would save mileage costs because of lesser GVW etc. You get the picture. Most fleet operators and owner operators want to streamline their day to day operation and if they can save money and have been reassured by the sales guy that everything is going to be great why not go for the non SCR option?
Hindsight will kick you in the butt sometimes and the issues with these engines are causing a lot of frustration and pain along with a skinnier budget.