Need Opinions on Cummins ISB6.7 on Freightliner M2

The 6.7 ISB is the default choice for all 3 north American school bus manufacturers. They haul all day, everyday. Great on fuel. As with most modern diesels the harder they work, the less emissions problems you will have.
They mainly have issues with the variable geometry turbo, and the usual def issues common with most new diesels. But the core engine is excellent.

 

Work on them almost every day. Weak spots are in the egr system. Small egr cooler and the differential ports plug up frequently. Egr valves along with ports can be removed and cleaned easily with a 10mm socket and a sharpened coat hanger. Overall a strong engine. Use a cetane fuel additive. You will be O.K.

 

I have one in a 2008 pick up that has been trouble free.
Your probably thinking “ yea trouble free in a pick up truck pulling no weight”
Well I pulled commercially with mine at a GVW of 45,000 lbs and it is now used for personal use pulling my 40 ft fifth wheel camper.
Honestly 12,000#s to that engine is a joke.
I also have a 2002 fl 60 Freightliner rollback with a 5.9 Cummins in it that has 446,000 miles on it and it has a GVW of 25,500 # and it also has been very reliable.

 

Pretty standard motor for that application. School buses, single axle medium duty trucks, etc.
The reason its only 220 horse is for longevity. In a pickup application they get the stupid high power and torque but they only do that because they know most of the time they are loaded light. Even in the Ram chassis cabs (the ones they put service bodies and flatbeds on) they are derated to a lower power rating as they know those will be worked hard, and lower power=longer life.
If you want to test it out call up Penske or Ryder and ask for a Freightliner M2 (should have an ISB+Allison, but make sure). Rent one for 250 a day, haul some typical loads with it, and see if the 220 HP is enough. To me, they are fast enough for a truck. I can merge without creating a hazard while loaded, and to me that's plenty fast.

 

We have the 325hp one in our bucket trucks, coupled with the Allison 3000 trans. I use the exhaust brake/jakes as much as possible, I find exercising the VGT on the turbo has helped it from sticking up.