Date:         Thu, 9 Jan 97 09:34:46 -0600
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Rocko Flamefart <-@--.-->
Subject:      ARCHIVES: distilled water + coolant

this was found in the archives... hint hint.
archives located at:

http://halfdan.med.umn.edu:8853/misc/archives/vanagon.html

>From: Rocko Flamefart <-@---.--->
Subject: Distilled water + coolant
Date: Fri, 11 Oct 96 11:04:08 -0500

Several people have suggested using distilled water in the vanagon cooling
system.  I would like to caution that this may not be a wise action
considering the corrosion problems given wasserboxer heads.

Water can be viewed on a continum as either scale forming or corrosive, with
the outcome being calculated as a "Saturation Index".  Since water in motion
tends to be corrosive, this water balance becomes critical in automotive
cooling systems.  To avoid corrosive conditions which can etch metal
surfaces, including aluminum of the heads and heater cores, all water
quality factors  must be within proper ranges.  Antifreeze manufacturers
take great pains to produce a product that buffers the coolant so that it is
neither corrosive nor scale forming.  This is achieved by striking a balance
between alkalinity, pH, and calcium hardness thru the addition of buffering
components.  

While these buffers do have an ability to compensate for varing water
conditions, the "best" water to add to the cooling system is one that is
already close to a zero saturation index, meaning neither scale forming nor
corrosive.  Distilled water, having no calcium hardness nor alkalinity to
speak of, is extremely corrosive.  It wants to pull ions out of contact
surfaces, including metal. By using distilled water, one does make it LESS
likely to have a scale form on the inside of the cooling system but it also
makes it MORE likely to be corrosive.  Seeing the corrosion of the sealing
surfaces on my heads after I removed them, I would err on the side of being
scale forming rather than corrosive.

So what water would be best to use?  I would seek a non-softened,
low-to-moderately hard well water low in iron.  How you find that is up to
your ingenuity but I have heard rumors regarding 1 gallon jugs of Autobahn
water selling for $6.00.  :) 

Lastly, those of you who have used distilled water, take heart.  Distilled
water, while corrosive, is also easily buffered by the antifreeze
components.  What you are left with in terms of the composition of the
coolant is a mixture that is buffered, but with some of the buffering
components 'used' to reduce the corrosivity.  A more neutral water would
leave those components free for buffering as the system becomes contaminated
with combustion gases, age, and Bars Leak. :)

-dan