Can anyone tell me what this hose is and were it goes?

It's a coolant hose for sure but what its cooling I don't know. It starts on the rear of the egr cooler close to the fire wall and then goes down to the back of the trans were it loops around and heads back to the front somewhere. Also does anyone have an idea on how to fix it other then replacing the entire hose because that is turning out to be a huge pia. 2016 cascadia dd15 10 speed. I downloaded 3 pic and it did what it did but you get the idea.

 

Well I figured out what it is. Took some pic's to freightliner and found out it was a supply line to the def tank. I guess maybe the pump in the def tank uses the coolant to keep it cool.

I spent hours trying to take the old line off and finally gave up and put the new line in around the old one. Took about 15 minutes. It worked and I was able to get the truck home were I will continue trying to get the old hose off.

All the clamps holding the old hose on are on top of the trans area which means I have to get a socket wrench and vice grips up over it from underneath blind. My hand muscle were continually burning. It was a pain is an understatement.

I was thinking about what you mentioned that is doing some sort of splice connection. I will keep your suggestions in mind for possible future situations.

 

Turns out it was a def coolant supply hose.

 

It was a def tank coolant supply hose.

 

Oh, ok I didn't realize that. Interesting stuff.