om603.971 hose replacement help

[wwii]

I need to replace a Y shaped hose, part number on the hose is 140-832-73-94. It is item 317 on the attached picture. One leg of the hose comes from the bottom of the engine, one leg goes to the bottom of the coolant expansion tank. I haven't been able to trace the third leg yet but I think it might go to the heating system, duo-valve.

Does anyone know where that third leg is connected?
How much coolant should I expect when I disconnect the hose, all of it?

Thanks much