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Does your rad "sip" from your overflow tank?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Can Can, Apr 26, 2002.

  1. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Does your rad \"sip\" from your overflow tank?

    This may be dumb, but I've never really thought about it before? When your rad gets overpressurized it will burp air(and coolant) out through the rad cap and into the overflow tank. I know that......../forums/images/icons/tongue.gif

    BUT......

    If your rad is a little low, does the overflow tank act as a reserve? Does the rad cap act as a vacuum and pull coolant back into the rad? If it does, can somebody explain the physics of it to me?
     
  2. Oblin Goblin

    Oblin Goblin 1/2 ton status

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    Re: Does your rad \"sip\" from your overflow tank?

    Yeah it will "sip" from the tank as long as radiator cap is on while the coolant leaks out of the radiator. When coolant leaks out of the radiator it creates a vaccum and the atmospheric pressure in the overflow tank pushes coolant in to take its place.
     
  3. HarryH3

    HarryH3 1 ton status Author

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    Re: Does your rad \"sip\" from your overflow tank?

    It's just thermodynamics in action. /forums/images/icons/wink.gif When water gets hot, it expands. The expansion creates pressure. Once it exceeds the pressure rating of the cap, it pushes past the cap and into the overflow tube and tank.

    When water cools, it contracts. The contraction creates a vacuum. If you look closely at a radiator cap, you'll see a small silver disc in the center of the rubber seal. The disc acts as a check valve. When the radiator is pressurized, the valve is closed. When a vacuum forms inside the radiator, the valve opens up and coolant gets sucked back from the overflow tank. /forums/images/icons/cool.gif
     
  4. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Re: Does your rad \"sip\" from your overflow tank?

    Thanks!!!/forums/images/icons/smile.gif I always wondered why the "silver disc" kinda wiggled around in the cap a bit. Check valve, eh?/forums/images/icons/cool.gif
     
  5. weisel

    weisel 1/2 ton status

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    Re: Does your rad \"sip\" from your overflow tank?

    I've always wondered how the coolant got back into the rad threw the cap also. Thanks. I didnt know it had a check valve.
     
  6. Morphgizmo

    Morphgizmo Registered Member

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    Re: Does your rad \"sip\" from your overflow tank?

    Thanks for the info Harry.

    I've been curious about that myself.
     

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