International and Navistar released their new line of MaxxForce diesel engines from the model year 2008. Included in the line were some ground-up new designs, as well as modernizing old standbys like the DT466 to meet the much-feared new EPA 2007 standards for commercial trucks. Despite sharing a naming convention, not a lot is shared between the MaxxForce engines. The smallest is the NGD MaxxForce 3.0 HS, a 3.0L 4-cylinder found in South American variants of the Ford Ranger, and the largest is the MaxxForce 15.

Before the MaxxForce series, International’s largest engines were the 7.6L DT466 and 9.3L DT570. With the launch of the new MaxxForce engines, there were suddenly 3 engines larger than that:

• MaxxForce 11: 10.5L, 365hp, 1250 lb-ft
• MaxxForce 13: 12.4L, 430-450hp, 1550-1700 lb-ft
• MaxxForce 15: 15.0L, 500-550hp, 1850 lb-ft

All three use compacted-graphite iron to reduce engine weight without giving up durability, and are available with a Jake Brake that works in conjunction with the trailer brakes and ABS system. They all use BorgWarner turbochargers and Bosch fuel injection to make their impressive power numbers, and EGR cooling and diesel particulate filters (DPF) to comply with EPA 2007 diesel emissions standards. The MaxxForce 13 and 15 are designed for long-haul Class 8 trucks like the International ProStar and ProStar+. The MaxxForce 11 is available in the TranStar, which is still a class 8 truck, but designed more for local or regional work.

Like many other International and Navistar diesel engines however, it can be plagued with EGR issues. When recirculated exhaust gases full of unburnt hydrocarbons mix with oil vapor from the PCV system, the resulting mixture can coat the turbocharger’s compressor wheel, VNT vanes or intake manifold runners, because it turns out that diesel exhaust gas is pretty dirty stuff. This carbon buildup can reduce the movement of these parts, leading to a loss of power. What’s unique about the MaxxForce engines is that the loss of power can become noticeable well before it triggers a low boost code, making diagnosis more difficult. By the time airflow through the turbocharger is restricted enough to cause a check engine light, there will likely be irreparable bearing damage, which means you may have to replace one or both turbos.

Most MaxxForce engines, including the 11, 13 and 15 use a compound turbocharger system. This is similar to the sequential turbo system popular on some sports cars from the 90’s, where there is one small “low pressure turbo” that spools up quickly for faster throttle response, and one larger “high pressure turbo” that spools slower, but flows a lot more air to make big boost and power numbers. The difference is that both turbos on a sequential system send air directly into the engine, but on a compound system, the smaller turbo sends its pressurized air into the larger turbo to help that one spool faster as well. A compound turbo system looks pretty wild under the hood of your truck, and for some applications like the MaxxForce 5 V6 ( more info on that turbo here ) they are typically sold as a complete compound turbo assembly that includes both high and low turbos in one unit. Because intake air contaminated with EGR flows through the low-pressure turbo first, that one chokes up a little quicker than the high-pressure turbo, but replacing both at the same time ensures better long-term reliability and lower overall repair costs if you would otherwise end up replacing the high-pressure turbo down the line anyway.

Because of the EGR issues with most MaxxForce engines, Navistar started updating them in the mid 2010s to replace that system with Selective Catalytic Reduction (SCR). The MaxxForce 13 became the N13, and the MaxxForce 11 & 15 were discontinued entirely; Navistar never took much market share from Cummins or Detroit Diesel in the Class 8 space, so it makes sense to streamline their offerrings. SCR is the name for urea injection, where a fluid is sprayed into the exhaust (downstream of the DPF) to react with and neutralize NOx emissions. Since this system is entirely downstream from the turbocharger system, you don’t have to worry about it causing damage to anything else; the only thing you have to keep in mind is refilling your diesel exhaust fluid (DEF) tank, which you can do at most truck stops these days. Unfortunately, this system cannot be backdated from the N13 to the MaxxForce 13.

The reputation of the MaxxForce engine line has hurt the resale value of International trucks, but it’s worth noting that the EGR is one of the few reported issues. We know that downtime can hurt even more than repair bills, but if you’re able to get the EGR cooler and lines serviced proactively (time it around your vacation days!), then a used MaxxForce can be a great deal for owner/operators on a budget, or for fleets who can rotate trucks in and out of service easily. When they work, they’re powerful and smooth, and paired with the aerodynamic improvements of the ProStar chassis, they can return excellent fuel economy.

The MaxxForce 11, 13 and 15 engines were equipped with more than one possible turbo part number from the factory, so ordering a replacement turbocharger can be a challenge. The best way to make sure you get the right turbo, the first time, is to use your International part number, or your BorgWarner part number to find a match ( See our guide here for more on how to identify your BorgWarner turbocharger ). We’ve put together a reference below that lists some of the most common International Navistar and BorgWarner part numbers for the turbos commonly found on these engines. In some cases, we offer both a brand new and a remanufactured option.

Contact Turbochargers Direct for professional assistance finding the correct turbo for your Navistar diesel! We have an extensive catalog of new and remanufactured, OEM turbochargers for all applications, including name brands like Garrett, Holset, Mitsubishi, IHI and more!