Register now to get rid of these ads!

The Two Types Of Radiator Caps - Confirmation

Discussion in 'The Hokey Ass Message Board' started by Tommy's Cycle, Sep 6, 2012.

  1. Tommy's Cycle
    Joined: Mar 22, 2006
    Posts: 766

    Tommy's Cycle
    Member
    from So Cal

    I was looking at some radiator caps, I have laying around, and noticed I had some older ones with no seal directly under the cap. Now from what I remember there are two types of caps: Vented & NON-Vented.
    First off, NO, a “pressure relief” lever on the top of the cap, does not make it vented and “ NO”, I am not confusing gas caps with radiator caps.
    As I understand a ‘Vented’ cap or ‘Closed System’ cap – means, as the system cools down, it will pull fluid from the ZERO PRESSURE recovery tank. ‘Closed’ meaning fluid is not released to the ground via an overflow tube. This cap will have “2” rubber seals.<O:p></O:p>
    A ‘Non-Vented’ cap or ‘Open System’ cap- means it will not pull fluid back into the cooling system. ‘Open’ means when the pressure gets too high it releases onto the ground. This type of cap will only have ‘ONE” seal on the brass pressure valve disc. Does everyone confirm this? I have seen guys add recovery tanks to their rides without changing to the proper cap. I'm sure running a vented cap on a system without a recovery tank is okay but it would pull air into the system upon cooling.
    <O:p></O:p>
     
  2. I have no idea.
     
  3. JohnEvans
    Joined: Apr 13, 2008
    Posts: 4,883

    JohnEvans
    Member
    from Phoenix AZ

    Yep you is 100% right ,recovery caps need the upper rubber seal to work correctly.
     
  4. Don's Hot Rods
    Joined: Oct 7, 2005
    Posts: 8,319

    Don's Hot Rods
    Member
    from florida

    Here is what Wiki Answers has to say about it:

    Look at the bottom of your radiator cap. There are two seals. One that seals at the top neck and one that seals at the bottom of the filler neck. As the fluid heats up it expands. It eventually over powers the primary spring in the radiator cap.

    The bottom seal is broken as the pressure exceeds the spring force of the cap and the cap rises. Fluid then enters the overflow tank until enough pressure is relieved to allow the spring to force the bottom seal back into place.

    You'll also find on the bottom center of the cap that there's a brass or stainless circle plate. That circle plate actually creates a one way check valve. When the engine cools back down the coolant shrinks in volume. As that happens the pressure in the coolant system becomes a vacuum pulling down on the bottom circle plate and thus opens the check valve.

    Once the valve opens the fluid is drawn in through the tube that leads to the bottom of the reservoir and refills the system. The system is actually self burping in that it evacuates air on each temperature cycle. Air is pumped out when the system gets hot and fluid is then drawn in when it cools.


    Don
     

  5. Tommy's Cycle
    Joined: Mar 22, 2006
    Posts: 766

    Tommy's Cycle
    Member
    from So Cal

    So the purpose of the top seal is to prevent fluid escaping out the top of the cap as it is pulled back into the radiator. Thanks Guys
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.