Cummins ISB Diesel Engine In A School Bus The Perfect Marriage

imported_John Whelan - March 28, 2018
I will not lie the Cummins ISB is the best diesel engine I've worked on that does not have nagging emission problems like their competitors. I should say what competitors? Not too many are left. International did not want to go with the SCR selective catalytic reduction in 2010 and decided to stick with Advanced EGR. This was a big mistake because the EGR system did not do the job and cost Navistar a lot of money to fix the problems it created. The MaxxForce engines came to a sad end a few years later.

Another victim of the diesel engine emission crunch was the Mercedes MBE 900 that also offered EGR only emissions. This design could not keep up with the amount of ugly soot and ash that was steadily pumped into the intake and exhaust accumulating on components and overloading the DPF (diesel particulate filter) that was supposed to perform passive regens (while driving) to combat the build up.

Mercedes eventually had to throw in the towel in 2010 not being able to keep up with the stringent emission guidelines put forward by the EPA. Our fleet still have MaxxForce and Mercedes diesel engines in the fleet and we have to keep an eye on the emission systems keeping them clean to avoid emission engine codes. A clean DPF is the answer for any 2007 diesel engine and newer. We have replace several along with removing and sending them out for cleaning.

Sometimes they fail the flow test at the dealer and a new DPF is the only solution. They are not cheap priced around $2400.00 while cleaning will run around $350. So I cross my fingers every time we ship one out. Since we started a few years ago emission codes have been non existent and that came from cleaning or replacing the DPF units. Preventive maintenance works for us as well. When we suspect an issue a parked regen is performed which takes approximately half an hour.

We have a spot on our service sheet to do a parked regen during a 15,000 km service but it just does not work out because of the time it takes to get the regen completed properly. Before a regen can be carried out the engine has to be at operating temperature which adds to completion time. However there is an alternative solution which is an extended highway run for 20 minutes. This is a manufacturer recommendation when the amber regen light shows up on the dash. Even better just purchase a Cummins ISB. As I stated in the beginning of this post Cummins SCR technology is the best way to avoid emission problems. I'm not saying problems will never happen but they will rarely come around.

School Bus
Diesel Engine
6.7 Liter