Yes, that's the one- - - -the small disc at the bottom allows the vacuum in the cooling system as the engine cools down to siphon coolant back out of the puke tank. If the tank is too small, it will fill up and overflow. A couple of quarts should be plenty, with about a pint of liquid in the bottom, with a full radiator and a cold engine.
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!