Ok so I started noticing random leaks in multiple places under the truck, so I went in for a closer look.
Nothing leaking around the degas bottle; deltas are good, performance is fine, egr not leaking.
Turns out I've got leaks all over the place. Some are clearly coming from various connection seals (mostly around the radiator), others I haven't been able to pin down.
I've taken pictures to illustrate:
These are from below the radiator:
Passenger side hoses:
This one is directly above the front differential, which I assume is a connection to the water pump:
There is another above the driver frame rail that I can't see.
Is this simply a bunch of failed seals and hoses or something more sinister at play?
Truck has 250k miles, and is not driven very much. Leaks only occur when truck is hot.