Pressure in radiator

Heating, Cooling & AC

  1. ksurfer2

    ksurfer2 Well-Known Member

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    I have noticed an odd condition in my radiator. 512 in motor with a be cool radiator/cap/resovior. I run distilledd water and water wetter only as this is primarily a track car. After normal operation, if the car sits for a week there will still be pressure in the radiator when I remove the cap. Not a whole lot, just enough to push a little water out. I keep the level in the radiator about 2 inches below the cap. I recently noticed that there was a bit of water on the floor under the radiator after the cat sat for a few days. Inspection revealed that the overflow resovior was full. Why is the radiator staying pressurized and not pulling water in the overflow back into the radiator after cooling down. Motor doea not run hot...typically 190-195 is as hot as it gets.
     
  2. diesel_lv

    diesel_lv FBBO Gold Member FBBO Gold Member

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    If you are using a 2 way cap that allows overflow to go to reservoir and then be suctioned back to radiator, then the radiator should be completely full and the reservoir tank partially. If it's a 1 way cap that allows overflow only, then the radiator should be filled to about 1-1/2" below bottom of filler neck. And no water in overflow tank, just the little that gets purged once or twice until the radiator reaches it's stabilized level. The cap is pressurized and will hold 14lbs. A very well sealed system can sometimes hold this pressure even after cooling.
     
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    • 493 Mike

      493 Mike FBBO Gold Member FBBO Gold Member

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      Do you have the correct double sealed cap? To use the reclaiming system the radiator should be full when cold, then as the coolant expands it transfers to the reservoir which must have space to accommodate that expansion. Then as it cools the outer cap seal will let a vacuum develop in the radiator which causes the reservoir excess to travel back to the radiator. Simple as a pimple! As far as pressure still in the system after complete cool down?
      Mike
       
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      • turbine68rt

        turbine68rt Turbine Bronze Member FBBO Gold Member

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        • khryslerkid

          khryslerkid FBBO Gold Member FBBO Gold Member

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          The Water Wetter causes a chemical reaction of sorts that creates the pressure. I experienced this with the Kool It product. It did seem to cause an etching effect on the casting and I noticed there isn't any rust in the cooling system. Looks like a good thing. After awhile it stopped doing this.


          https://www.forbbodiesonly.com/moparforum/threads/under-pressure.139484/
           
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          • WileERobby

            WileERobby Well-Known Member

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            • khryslerkid

              khryslerkid FBBO Gold Member FBBO Gold Member

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