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In a liquid cooling system that has no
*non-condensible* gas (i.e. air), the pressure will rise due to thermal
expansion of the liquid, until it gets to the pressure relief value of the cap,
at which pressure a small amount of the expanding liquid will go into the
overflow bottle.
Upon cooling, the liquid volume shrinks, and the
pressure decreases until it is lower than that in the bottle, and liquid is
sucked back into the system. If the bottle is pressurized, then the
pressure in the system will only go down to the pressure of the bottle. This may
be what is being described in Dave's system.
Dave, do you have a *pressurized* overflow
bottle?
Bill Schertz
KIS Cruiser # 4045
----- Original Message -----
Sent: Wednesday, June 08, 2005 9:31
PM
Subject: [FlyRotary] Re: coolant
leak
After you shut off your engine, the 7 psi gradually drops over the
next few minutes. It only takes around 12 minutes for the system to develop
a vacuum relative to atmosphere. At that point the little valve in the
radiator cap opens and allows fluid or air to flow into system. (Check out
your rad cap, can you find both valves?)
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Al, if your cap is a 24 psi cap which you said you could run with full
bottle. Why does it develop a vacum on cool down. I have never noticed this
on my system, but on the other hand probably never looked at it 12 minutes
after shutdown
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