The ISB6.7L Cummins seems to be the popular choice for school bus application prevailing over Navistar’s MaxxForce DT and a less popular Mercedes engine platform.
Equipped with a Bosch high pressure common rail fuel system as well as a Cummins/Holset HE431VE turbocharger, the Cummins platform is suited well for student transportation. The fuel system seems to be more robust than the MaxxForce DT as long as there’s no issues with fuel contamination. Bosch continues to refine its high-pressure pump, fuel rails, and injectors, providing the best engineered fuel system in the industry.
The VGT Holset turbocharger has been a common failure point for this engine, mostly related to soot buildup in the exhaust housing causing the VGT mechanism to stick and fail the actuator. Holset has made improvements to the design since the initial release in 2007.5. In 2012, Holset upgraded the actuator and made changes to the center housing, adding an additional piston ring to both the compressor side and the turbine side.
We hear a lot about the emissions systems in the exhaust as well as a plethora of EGR Valve/Cooler complaints. Yes, these problems are a pain and do cost transportation companies thousands of dollars. However, some preventative maintenance and tackling those check engine lights early can provide huge cost savings. These problems snowball, so take care of the root cause early and you could save big later.
The latest Thomas, Bluebird, International buses are typically equipped with an ISB6.7L 220. At an advertised 220 horsepower and 520 ft-lb of torque @ 1600 RPM, this should be everything your bus needs to take your students from point A to point B safely.
Have questions about maintenance? Looking for a quality aftermarket parts supplier? Contact us, and we can share our cost and downtime reduction program with you.