Sheesh, like tires this thread raises its ugly head every so often, with no
reference via the archives of what was said before!

couple of things...

if you have hard water coming out of your tap, use distilled or deionized
water in the cooling system (btw, distilled water is not produced by the
same process as deionized water)

if you have cheap access to RO/deionized water use that if you like (I got a
rise out of J. Walker when I mentioned that I use 18Mohm water, overkill).

The calcium sulphates/carbonates, the magnesium and iron compounds found in
what ever variety of hard water you're unlucky to have will form
precipitates in the cooling system. These ppts will coat the surfaces of the
system reducing the heat transfer and eventually occluding the narrower
passages (ie rad) in the system. Modern coolants have scads of additives
that help reduce this precipitation problem (and control pH), but why not
start with low mineral content water to begin with?

Oh and an outboard motor using lake or salt water as coolant is not the same
as a closed loop automotive cooling system.

Alistair

albell@uvic.ca
http://homepage.mac.com/alistairbell

'82 Westy, diesel=>I4 gas

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on 17/2/02 7:03 PM, you  wrote:

> Balderdash.
>
> Neither Bently nor any VW dealor or independent service shop in the 15
> years that I owned my 85 GL ever mentioned a requirement for deionized
> water.  Using distilled is nice since it's clean and not hard, and is
> often produced by deionization, but it is NOT required.
>
> William,
>
> Don't believe everything you read on this list. If someone with the
> credentials of Steve Not A Jeep Denis or Boston Bob want to contradict
> me I'll take it.  But my BS detector really went off on this one.
>
> Ed
>
> Rico Sapolich wrote:
>
>> In a message dated 2/17/02 12:49:43 PM, developtrust@HOME.COM writes:
>>
>> << What is the rationale for distilled water. >>
>>
>> The cooling system requires deionized water.  Although I would think that
>> distilled water is also deionized, I slept through too many analytical
>> chemistry classes to have any meaningful knowledge of the matter.  I imagine
>> that deionized H2O allows the additive components of the antifreeze to
>> function as was intended by the chemists' formulation.
>>
>> Also, deionized H2O is offered by antifreeze manufacturers at inflated
>> prices.
>>
>> Rich
>>
>