Why am I losing a quart of coolant every week on my 2016 Cummins when there are absolutely NO leaks on the driveway?

[OpenRoadOutlaw]

I’ve got a mystery coolant leak on my 2016 6.7L Ram 2500 (110k miles). Every Saturday, the low coolant light comes on, and I have to dump almost half a gallon of Hoat coolant into the reservoir. I’ve crawled under the truck with a flashlight a dozen times—the water pump is bone dry, the radiator hoses are perfect, and my driveway doesn't have a single drop of fluid on it.

I pulled my engine oil dipstick, and the oil looks normal (not milky), so I don't think it’s a blown head gasket. Could the factory EGR cooler be cracked internally and slowly dripping coolant straight into the exhaust stream where it just vaporizes out the tailpipe? If it is leaking into the intake side, am I risking a hydro-lock if I let the truck sit over the weekend? How do I pressure test this POS EGR cooler to know for sure?

 

[Pipemods_02]

You don't need to completely remove the EGR cooler to test it. Here is the easiest shop trick to prove it's the culprit:

1. Go to Harbor Freight or an auto parts store and borrow a Radiator Pressure Tester kit.
2. With the engine completely cold, unbolt the EGR valve (the black electronic top hat held on by 4 bolts on the intake elbow) and pull it out. Look down into the chamber with a flashlight. It should be bone dry and covered in dry, flaky black carbon soot.
3. Now, pump your radiator pressure tester up to 20 PSI on the coolant reservoir tank and watch the gauge. If the gauge slowly starts dropping pressure, shine your flashlight back down into that open EGR valve port. Within 5 to 10 minutes, you will literally see wet, green/purple coolant bubbling or pooling at the bottom of the dry soot chamber. If you see that, the cooler is officially dead.