Hey all. I installed a new radiator on my 97 Suburban (5.7) a couple years ago. There's a rubber cap and hose clamp blocking off some kind of outlet below the radiator cap and overflow line. Recently, the rubber cap blew off and I lost a bunch of fluid. Does anyone have any idea what the purpose of that "outlet" is?

 

Maybe a secondary heating system? Turbo cooler? Rabbit hole?

 

I've wondered about that. Right now I'm going with rabbit hole!