Kw t660 antifreeze issue

I have the same problem. .kw is starting to suck..but mine was a tiny pin hole by the radiator

 

Most coolant leaks are found when cold and at low pressures, less than 5 lbs, I use to put the unit outside with an rad preasure tester with a hose to a regulator and connected to shop air. I would wash the unit as clean as posible every wear, remove the cover from the bunk heater and be sure the drain hose for it is open, also the cab heater drain hose. Remove the turbo outlet, and if no coolant is found externally, then start the unit with a paper on a clipboard, to see if it is internal.
Just a thought!

 

The egr cooler is on the pass side behind the turbo. Look at the pipe on the back side . it goes to anothe pipe that goes around the back of the enigine. Where the two meet it has two bolts. Take those two bolts out and if its wet in there at all then you got a bad egr cooler.That pipe should be exhaust only so its common to have soot but not wet soot. Common problem , even new ones are found bad . If its nice and dry then I`d look to see if your bunk heater core is leaking . Look under the cab and see if any coolant is dripping where your heater hoses go in