Can someone tell me exactly what this is called???

[dhirocz]

That has nothing to do with the engine...not directly anyway. I pull tanks and I have a set of those behind my cab, they are quick connect couplers used for running in transit heat to a tanker trailer.

I picked up replacements at tractor supply. Most hydraulic and marine shops carry them too. Most are tee'd in at the heater core in the bunk.

I can't tell where those are installed in the pics, but hopefully that helps. I have no idea what else those could be used for other than ITH, but all I've done is tanker...