"Closed Cooling System" Definition: 1971 GS 350

Discussion in 'Small Block Tech' started by Jolly-John, Feb 24, 2019.

  1. Jolly-John

    Jolly-John Well-Known Member

    I'm a bit confused about the wording on the AC radiator cap for my 1971 GS 350, with factory A/C and plastic coolant recovery tank.

    The stock radiator cap reads "Closed System". I thought the definition of a closed cooling system is one that includes a pressurized coolant recovery tank. Of course, the factory plastic recovery tank on my '71 GS has a simple flip cap for use in adding coolant to the tank, and is not pressurized.

    So, in reality, why isn't this an open cooling system in my GS? And, therefore.....why would the stock AC cap be labeled "Closed System"? My car is sleeping for the winter, but I've included a general photo of what the stock AC cap and wording look like. Thanks for any input on this. John

    aacc.jpg
     
  2. BuickV8Mike

    BuickV8Mike SD Buick Fan

    Its a closed system until the over pressure release in the cap vents off pressure if it overheats.
     
  3. 1973gs

    1973gs Well-Known Member

    Back in 1971, if it had a coolant reservoir, it was a closed system. As the pressure built up in a closed system, coolant would go into the reservoir. When the engine cooled down, coolant is drawn back into the radiator as long as the hose in the reservoir went to the bottom of the reservoir. An open system would just expel coolant on the ground. Today's modern cooling systems are truly closed where the reservoir, or surge tank are pressurized.
     
    Mark Demko likes this.
  4. Jolly-John

    Jolly-John Well-Known Member

    Ah ha! So, it appears the strict definition of what a "Closed Cooling System" is has changed from the 1970's to today. That makes sense, and eliminates the confusion I was having. Thanks for taking the time to reply, Guys. John
     

Share This Page