So, I was just reading elsewhere where some one asked about their overflow tank being empty and their van overheating, etc, and it brought a question to mind.  
I get so much good info here on The List I thought I'd ask here first...

When the coolant overflows into the tank, does it draw back into the engine when it cools, like other vehicles I've had?   Curious to know because my thought is that ,if the engine is getting hot and there is none in the overflow tank, I assumed I could just add some to the tank and it would draw into the engine.

Is this so, or is there something I don't know.  I mean, I know i don't know stuff ;) but I need to know, ya know?  

Thanks 

Roman