Coolant (especially a 50/50 mix of antifreeze and water) does a lot of expanding as it heats up. Unless you have a catch tank, it dribbles out of the overflow tube. There are lots of ways to catch and recycle the expanding coolant, depending on how "stock" you want things to appear under the hood.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!