Re: [AMC-list] quiet in here, 195.6 ohv cooling system

[Frank Swygert <farna@xxxxxxx>]

I found a chart for plain water. Each psi over 15 psi (atmospheric pressure) raises the boiling point by 3° (212°F at atmospheric pressure). BUT, anything added to water will increase the boiling point/decrease the freezing point. So the ethylene glycol has that effect too.

http://www.engineeringtoolbox.com/boiling-point-water-d_926.html

Check this Wikipedia article out! It has the boiling point vs. concentration of ethylene glycol (anti-freeze). Assuming that the boiling point is raised the same as water a 50/50 mix would boil at 225° + 3° for each psi over 15 psi (14.7 psi).

So a 13 psi cap won't work -- I run a 16 or 17 psi cap, which only adds 3-6°. Somehow that doesn't sound right. I know some engine run around 250° without boiling over. Is a radiator cap rated at psi over atmospheric? Then a radiator would run 225° + 36° (261°) with a 13 psi cap and 50/50 mix... which sounds about right...

---------------------
Date: Sun, 18 Jul 2010 22:14:01 -0700
From: tom jennings<tomj@xxxxxxx>

>  " But 50/50 boils at 223F,
>
>  open air, or under the cap?

Oh right, 223F B.P. at atmospheric pressure. I can't seem to find a credible
chart or formula for pressure vs. B.P.  but two random pages stated 48
degrees increase in boiling point at 15psi.

So coolant is NOT boiling in the head at 230F, so that is unlikely to be a
problem.

Still gotta find a chart or formula for this, but thanks Andrew!!

--
Frank Swygert
Publisher, "American Motors Cars"
Magazine (AMC)
For all AMC enthusiasts
http://www.amc-mag.com
(free download available!)

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