Can't find coolant leak dd15 cascadia freightliner 2018

I had the same exact issue, same truck and engine but it ended up being my EGR cooler. Best of luck.

 

The lines to the compressor these guys mentioned are notorious for this. Might still be warranty depending on your coverage.

 

They have improved those 2 lines and made them rubber instead of plastic. Only like $25 or so each. All Cascadia owners should swap them out at home base.

 

Did you ever find the problem ??

 

Pressure test the EGR cooler. There's a Detroit tool they cap it off with and then pressurized with air. Note: you're NOT pressure testing the cooling system. Some newbie mechanics won't get it. If it's leaking it's likely dumping coolant downstream into your One-Box, which is highly corrosive strainer the precious metals inside it. That's a $20,000 repair at the end of the day.

You could also remove the inlet pipe at the back of the cooler and most likely coolant will be evident.