While topping the coolant tank reservoir, I slowly and carefully intentional overfilled and I notice water coming out this nub area that appears to be a weep hole? Is that an overfill outlet or weep hole?
Its my understanding, that no part of the reservoir should be open to atmosphere and if any part is there is normally a check valve type gasket involved.. I cant get a clear look - so tight in there..

 

Never heard of a weep hole in the tank just on the water pump

https://www.rockauto.com/en/catalog/...ery+tank,10457

 

You understanding is wrong. That is not a reservoir it is a recovery tank. The seal is at the pressure cap on the hose.

It should only come up to the indent in the tank when cold.

Here is a thread about the same subject:

https://www.chevyhhr.net/forums/ss-s...y-20118/page3/

 

And here is a good pic of where the coolant level should be when cold.

 

Thanks RJ. I couldn't find it.

 

I keep thinking it's in the how-to section, but it's stickied in maintenance(where it should be!).

 

Seall is at the pressure cap on hose..
That says it all..
Thanks