Posted 2019-11-29 12:09 PM (#590908 - in reply to #589370) Subject: RE: Is a 58 plymouth supposed to have a radiator overflow plastic jug?
Location: Hilltown, PA
This was a very common "update" during the 60's and 70's. Most auto parts stores offered universal kits which included a plastic (or sometimes metal) overflow tank, and a pressure/vacuum cap. The O.E. caps on our cars will generally not draw fluid back into the cooling system, so the kits included one which would.
While not "correct" an overflow recovery tank has several benefits - it helps keep air out of the cooling system which can prevent air locking the heater core or thermostat. It keeps the car rom pissing coolant all over your nice clean garage floor or driveway. And it lets you check the coolant level with a quick glance at the plastic see through tank, rather than opening the radiator cap.
Most importantly, however, is that many venues require them now. Pretty much any facility with a race track will not allow a vehicle with an "open" system onto the racing surface - including show vehicles. Several show facilities with both paved and unpaved display areas are at least requesting them to prevent the discharge of toxic material onto the ground.