Cummins ISB Engine life

Same engine as in the Ram pickups.

 

ISB is the only diesel engine in all school buses since about 2015. Everyone thought they were the cats meow, especially compared to maxxforce offerings. My experience is meh. They are great when new, but when the miles pile on they are no better then anything else.
Lots of them with 500+k miles on em out there.

Freightliner and International both have bulletins on grid heater bolt failure
Same as rams. From my understanding the relay is the root cause, it sticks on and burns the bolt. The bolt drops into the intake and chaos ensues.

I've seen piston rings break on high mileage units (500k km+) and score the cylinder. They are a parent bore engine, not wet liners, so the block either needs sleeving or junk.
The emissions crap is the same as any other, most manufacturers use cummins aftertreatment (paccar, International etc).

We own an ISB. Cummins spent 23k on warranty on the def system alone under warranty. It's not illegal to delete where I'm at, I had it deleted as soon a warranty was over. 3 years of trouble free, fuel efficient operation since. Ours has 240k km on it. Runs mint.

Dam near the same as a ram pickup, except ram has the geartrain at the front, med duty Isb geartrain is at the rear.

Summary, the Isb is like franks hot sauce. They put that #### in everything now, because it's the only one made for the market, and was better then everything else...

Except for Freightliner and their DD5 and DD8s. And those are going away.. and everyone I know that has a dd5, wishes they didn't.

 

A loaded to max gross class 7 box truck will work that little engine harder than a Dodge ram ever could and they will never get the mileage and life they do in the pickup. We had some Ford F700’s with ISB’s and at around 250,000 to 300,000 mi they were wore out. Lost tons of power and used a gallon of oil a week. That is running in south Tejas heat and pushing coastal bend wind with 24ft Supreme boxes. We’d get around 475,000 out of a Cat 3126 and it was done.

 

All of our box trucks are either Peterbilts or Kenworth's with PX7 or PX9 motors which are rebadged Cummins engines. We have a PX9 pushing 539K miles, a couple of PX7's over 525K miles and 1 getting ready to hit 500K miles. 2 more are well into the 400K miles. We change our oil every 5k - 10k miles, and we run mostly the East Coast from NC to ME so lots of traffic. Never had to rebuild an engine but lots of turbo actuators, a few turbos and pretty much every engine has had new injectors which are not cheap.

We have Freightliner on order for over a year and half through Penske to replace the truck with the most miles and we opted for the Cummins engine in that. We are also looking at ordering another 2 Peterbilts to replace the trucks with over 500K as our Peterbilt dealer says truck ordering is finally loosening up.

 

It’s not a bad engine but personally I’d stay away from it because it’s not a good application for it in my opinion. I used to work at a shop that had serviced school buses and the 3126 cat provided much better results all around for us. I have a f700 with a b5.9 mechanical and can’t really complain but I sure wouldn’t want to use it otr so to speak. It’s under powered and thirsty for oil although a considerable amount goes out the front cover it’s got around 150k on the clock.