so i was replacing the serpentine belt, and while i had it off, i decided to spin each component powered by it to make sure i didn't have a bearing going bad someplace. the water pump seemed a little stiff, so i popped it off to take a look. it turns smooth, but has a bit of resistance. which depending on the seal type they are using, i guess must be normal? I think the water pump is ok, there was no leaks. anyway, when I was cleaning up the sealing surfaces, I noticed this 3/8 or 1/2 npt threaded (my npt eyecrometer has not been calibrated in some time, lol) hole right smack dab in the center of where the impeller sits. if it was just a hole, I would think it was just how they were getting coolant thru the engine. but threading a hole, makes no sense unless your going to secure something into it, like a ****** or a pipe plug. I have to wonder if it is missing a plug. does anyone know???