Big Block Dart Cooling

Watching Kindigit on velocity right now and very intresting they put the system in vacuum then suck the coolant in leaving no air! Mine burped twice after changing to the Flowcooler and high flow t-stat. It has not done it again. Temps today were around 90 and no issues for a 30 mile cruise either direction.
Which episode? What kind of vacuum? I didn't burp mine yesterday after changing the T stat. Probably need to do that.