Al, your experience with the value of having an air cushion is supported by
every automotive cooling system that I have ever seen (many).  Typically
autos use either a pressure cap and expansion tank that is not filled to the
top, or an overflow bottle into which coolant is expelled and recovered.  I
get the impression that some people assume that these overflow style systems
contain no vapour when cold, I don't think that assumption is correct.  The
overflow systems all have expansion capacity built into the top of the
radiator, or some other part of the cooling system they are never completely
filled with coolant.  The bigger the cooling system the greater the volume
of vapour stored cold.

-- Ian

(GM, Chrysler, and Ford are not trying to piss you off with those side
mounted radiator caps.. ;-)




-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]On
Behalf Of al p wick
Sent: Sunday, June 26, 2005 11:58 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Coolant Leak


My focus is on flight safety. I found great value to having appx. 1 cup
of air at the top of my cooling system....