2010 isx burning coolant?

[Dmurphy16]

I’ve got a 2010 t800 with a Cummins isx. Bought the truck a few months ago but it’s been sitting. Finally getting around to getting it roadworthy. Took it out for a short ride about 20 min. While driving it was puffing white smoke, and the coolant level alarm came on. When I got back the coolant reservoir was empty, so I added 2.5 gallons or so. Took it for a ride again and same thing. Coolant is getting into the exhaust and being burnt. from some quick research it can be many things; head gasket dropped liner, egr cooler.
Service records show the truck has had coolant loss issues in the past, it’s been pressure tested, no loss, ruled out internal/external leak. Radiator has been replaced.
I am thinking it’s possibly EGR cooler? I would like to start trying to diagnose so I can figure out if it is the cooler I can send it to the mechanic to replace it, but know it won’t be cheap.
any suggestions?

[tree98]

Pressure test the cooling system to 20 psi and look for external leaks, also disconnect the egr cooler so you can see inside it for leaks. If you don't see anything you'll have to drop the oil pan so you can look for leaks from a dropped liner or leaking injector cup.
Don't assume there's no leaks because someone else says so, verify it yourself.
Using that much coolant should be easy to find it.

[hhow55]

Very well could also be the aftertreatment fuel injector is leaking coolant, or an injector o-ring or injector sleeve is damaged.........Quickserve.cummins.com has info on how to properly diagnose these potential problems.