Yes, I am aware that the radiator is a problem with a 6.4. After a few weeks, the level drastically drops even though there is no sign of a breach. Do pressure tests work well for locating specific objects?
7 Likes
I have one that’s leaking into the oil pan and I am hoping it’s coming from under the front cover. I was in a pinch for a truck and bought this one sight unseen, advertised as a new motor. It arrived with the coolant light on.
6 Likes
Here is a 6.4 dude. If you have not already, proceed as though everything is leaking and take care of it all at once.
5 Likes
Check around the seams of the radiator, they often come uncrimped.
4 Likes
If you have a small leak, check for residue under the lines or beneath the engine. It can be tough to track down, but a residue trail helped me find a tiny leak on another car with a similar issue. I was losing coolant slowly, but it was not mixing with the oil or exhaust (that I could tell). It turned out to be the water pump. That is the best advice I can offer. Good luck. 
4 Likes
Ensure that it is not entering the crankcase through front cover pitting caused by water pump cavitation.
3 Likes
Head gasket is my guess 
2 Likes
You’ll need to check whether you can get the O-rings separately or if you should replace the coolant hose as a complete assembly.
1 Like
O rings were changed, and it is holding. I’ll give it a couple more days and provide an update.