I'm wondering about a little gizmo on the side of the radiator on my 91 Legacy. On the right side of the radiator, a couple inches below the air bleeder screw is a recess, maybe 1/2 0r 5/8" in diameter. In the center of that recess, is a stem, that appears to be a hex shape. I'm at a loss as to what this thing is ??

I looked at mine and have no idea. If I had to guess, I'd say it is a reinforced portion of the plastic side panel to accept a sensor or transmission cooling line for another car make. The hex may just be a spru from the molding process.