Should I worry about a def system flush on a used Freightliner Cascadia?

[Jason_T]

I’m looking at a used 2019 Freightliner Cascadia and the service records show a recent DEF system flush. The seller says it was just preventative, but I’ve always heard that if you need to flush that system, it usually points to a bigger underlying problem that’s already done damage.

[Benjamin_W]

I wouldn’t rush to call it a red flag just yet, but I’ve seen DEF flushes pop up after what amounts to a contamination scare. Usually it’s tied to sensors or the SCR aftertreatment acting up, not the flush itself.

[Chloe57]

I know a guy who bought a 2019 Cascadia and the shop did a preventive DEF flush; a few weeks later the truck was fine, and the buyer felt reassured, but it made me wonder if it was just packaging for other fixes.

[RyanQJ]

If you’re evaluating, ask for the exact codes before and after the flush and what parts were touched. In my own bid, the bill was vague and I walked away.

[MatthewYT]

Could the real issue be something else, like a leaking line or a faulty sensor, rather than the flush itself?