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  1. #1
    Registered Member chevynut's Avatar
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    Radiator caps

    I have a PRC radiator that came with a 16# radiator cap with a billet cover on it. I have a hose from the radiator overflow connection to the "recovery tank" that I built. The hose is high pressure hose and goes into the bottom of the "recovery tank". The PRC cap doesn't fit under my radiator cover since it has the billet cover on it, and I need just a plain radiator cap there.

    Should the cap on the recovery tank be "vented" to atmosphere, or pressurized? I think some systems have an "open" or low-pressure cap on the radiator and the external tank is called an "expansion tank", which is pressurized. The coolant flows into the tank when hot and gets sucked back into the radiator when cold. I'm thinking of using that PRC cap on the "recovery tank" and getting a plain one for the radiator. If I can do that, what cap should I get for the radiator?

    I read through this and it confused me even more. I don't know what they mean by a "vented" cap. My first thought was that it was "open" and allowed unrestricted flow. But another source said it was pressurized but would vent at some maximum pressure.

    https://blog.championcooling.com/201...xpansion-tank/

    They say an "overflow" or "recovery" tank/reservoir is "vented", and allows coolant to go back into the radiator through a "vented" radiator cap. But they say the "reservoir" is "vented" too.

    Then they go on to say an "expansion" tank is different. They say the tank is vented but the radiator cap is "non-vented". Also they show the tank connected to a radiator hose, which is pressurized. So how does a "vented" tank maintain pressure?

    Not sure how I should set mine up. Would having both 16# caps work?
    Last edited by chevynut; 01-20-2023 at 12:23 PM.
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