2014 T680

Drop the oil pan and check there for the missing antifreeze. I had a vehicle once that was losing antifreeze but no signs of where it was going. Even the shop could not find the leak. Once the pan was dropped everyone knew where the fluid went.

 

If it's not coming out , it's going in! Most likely a EGR cooler. Any coolant being burned will quickly ruin the DPF .

 

The DPF is a filter in the exhaust that catches any soot , or any other material in the exhaust . Major part of the emissions system. About a $3500 part.

 

Did you check all of the clamps in the cooling system for being tight? Had the same problem w/ my 2014 Pete w/ a n ISX. No drips or evidence of a coolant leak, thought it was going into the after treatment system. Turned out to be a loose clamp that only leaked when the engine was warm and wound up a bit under load. Not much of a leak, but I guess a few drops an hour adds up....

 

Mines in shop now 2nd time. Losing a gallon every 3 days. Looks like a tube on pass side frame.

 

If the DPF throws a code, a code for "EGR - Disabled" automatically pops up. When the EGR - Disabled codes is active for 10 hours, it will go into a derate. Eventually it will derate all the way down until a level 4 extended, which is a top speed of 5 MPH.

 

With less than 20k, it'll be a warranty matter for Kenworth to deal with. Aside from the aforementioned, the two coolant lines to the DEF doser often go overlooked.. be sure to check those, as it's not unheard of for leaks to form there. Don't know if yours has an APU or not, but where the coolant line connects to the APU always seems to be a trouble spot for our trucks, as well (T660s and T680s, both). And, if you do have an APU, also check inside the APU.
The PACCAR engines have a bit of notoriety for running through EGR coolers, although a lot of changes were made to the 2014 engine (perhaps the first one I noticed was the placement of the dosing injector), so I can't really speak for the current models.