Kodak Radiator leak

Anybody have a problem with a radiator leak on a Duramax diesel on a Kodiak chassis?
It only leaks after it sets for a few months. I can't seem to find where it is coming from. It seems too pool under the driver the radiator on the floor on the drivers side.

I'm about to take in to a Chevy dealer to take a look at it. Just wondering if anyone had some ideas.