Should I worry about a diesel smell in the cab when idling the Cascadia?

[SofiaG]

I’ve been running a 2016 Freightliner Cascadia with the DD15 and lately I’m noticing a faint diesel smell in the cab when I’m idling for a long time, like during my mandatory rest breaks. I can’t see any obvious leaks on the ground or wet spots around the engine bay, and the exhaust seems normal. It’s not overwhelming, but it’s enough to make me wonder if something’s starting to seep.

[Aurora_M]

I had a faint diesel smell at idle once on a Cascadia. Nothing obvious on the ground, but after a day I spotted a tiny drip on a fuel line clamp; swapped it and the odor faded for a while.

[James_A]

Kept looking for leaks and never saw a puddle. The smell would sometimes show up near the firewall where the exhaust lines run, with a little soot but nothing solid to pin down.

[Ethan60]

Thought it might be a gasket or turbo seal, but it would come and go and I never found a wet spot.

[EvelynDT]

If it’s from a long idle, I’d check the cab seals and firewall area, maybe something is letting exhaust get into the cab when everything is hot.

[BenjaminRR]

I even tried cracking a window during rest to see if it reduced the odor, and it did a bit but the smell still hung around.

[Joseph.W]

Question: have you checked the exhaust flex pipe under the cab for a leak where it passes the firewall?

[Luna_W]

If it keeps up, a quick pressure test of fuel lines and a look at the injector return lines might catch a tiny leak that isn’t obvious while running.