Cylinder 6 Failed

[Envirotec]

Hi All,

Our 2018 Freightliner Cascadia with a Cummins X15, which has approximately 17,500–18,000 engine hours, was found to have oil leaking into the exhaust manifold on all six cylinders, with cylinder #6 being the worst. What initially led us to investigate was the truck repeatedly setting 1922 codes and eventually derating or shutting down due to DPF-related issues.

We performed an EGR tune-up, cleaned and replaced DPFs and DOCs, but the problem persisted. At that point, I concluded the source of the issue had to be upstream of the aftertreatment system. After tearing down the engine, we found that cylinders 1–5 had liners and rings that appeared to be in good condition. However, cylinder #6 had a broken ring, and the liner was completely smooth with no visible crosshatch pattern remaining.

In addition, two other tractors in our fleet have recently failed the Cummins Insite cylinder performance/compression test, and in both cases only cylinder #6 failed. These are three separate X15-powered trucks (model years 2018, 2020, and 2020), all exhibiting issues related to cylinder #6.

I am beginning to believe that many of the recurring 1922 and DPF-related issues on these trucks may be the result of engine wear rather than the more common causes associated with the EGR or aftertreatment systems. My question is: why does cylinder #6 appear to be failing on all three X15 engines? Is there a known reason that cylinder #6 experiences accelerated wear or lower compression on these engines? Is this condition preventable, or is an in-frame overhaul ultimately the only solution once these symptoms begin to appear?

Thank you in advance!