Larry,

Good point.  I used distilled water.

I think you are right about the need for oxygen.  The area that corrodes is
pretty large.  It runs from the edge of the heads inward quite a bit.  I
have never seen corrosion at the edge of the head where coolant contacts the
head.  I sure have seen it at the outer edge.  Again, I think that
condensation builds under the gasket and surely the moisture has oxygen in
it.

Walt Spak
Pittsburgh PA
b20swalt@city-net.com
----- Original Message -----
From: "Larry Alofs" <lalofs@RCN.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, May 01, 2004 11:56 AM
Subject: Re: Cooling strategies, color coded, etc.

> walt spak wrote:
> >
> > I have put over 60,000 miles (trouble free, by the way) on my Boston Bob
> > rebuilt 2.1 and 40,000 miles on my 84 Westy with green coolant and have
no
> > leaky head gasket yet.
> >
>
> Ah, but did you use tap water or distilled water? :-)
>
> Let me add .02 to whatever theories are being developed.
>
> If the main corrosion product at the edge of the heads is aluminum
> oxide, oxygen is needed for the reaction to happen.  Any oxygen
> initially dissolved in the water used to mix the coolant should be
> depleted before too long and things should reach a steady state in a
> closed system.
>    But at a poorly designed seal at the edge of a head, a little seepage
> of coolant might occur and a little oxygen may diffuse in from outside
> as the expansion and contraction from thermal cycling moves things
> around slightly.
>    So now we have aluminum, oxygen, heat, and water along with dissolved
> minerals which make it more conductive and may even catalyze the reaction.
>
> Of course to keep our corrosion inhibitors fresh we should all change
> our coolant, and while we're at it:
>    change the brake fluid
>    change the fuel lines
>    change the coolant hoses
>    change the blinker fluid
> .
> .
> .
>
> Larry A.