Date:         Fri, 4 Apr 2003 00:11:09 -0600
Reply-To:     Joel Walker <jwalker17@EARTHLINK.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Joel Walker <jwalker17@EARTHLINK.NET>
Subject:      Re: Goofy Coolant Refresh Idea
Content-Type: text/plain; charset="iso-8859-1"

> Every month, simply drain out 1/Nth of the coolant from one of
the drainable
> spots. Replace it with a fresh 1/Nth of proper coolant/water
mix.  At any
> given time coolant in the vehicle still has an average "life"
of N months.
> Of course, I'm assuming the coolant of different ages mixes
perfectly.  I
> have no reason to believe it wouldn't. It is never perfectly
new, never
> completely spent.  Actually, Nth interval can be multiple
months, if so
> desired, as long as the "averaging" process is unaffected.
> What you think, eh?

i kinda doubt it would be effective .. reason being, what you
need to prevent corrosion is a level of concentration of the
additives. same thing with lubricating the water pump. say the
level of concentration has dropped to a dangerous level just
prior to your adding an additional 1/N coolant ... that much new
coolant might NOT be enough to bring the concentration back up to
protective levels. :(
the idea is to put a full concentration in, then do it again
before the coolant additives drop below a level that can still
protect.

let's see what we can figure out ...
we've got about 18 liters of coolant. figure a 50-50 mix and
that's 9 liters of antifreeze and 9 liters of water.
so we'll make up some number and call that 100 percent = 0.5
(concentration?)
they tell us that we should change the coolant every two years.
that the additives will be totally depleted in three years.
that's 36 months.
to go from 100 percent (0.5) to 0 percent (0.0??) in 36 months
means, if it's a linear process ... depleting the same amount or
percentage each day or each mile, that we can expect 100/36 or
2.78 percent loss of additives per month. or 0.5/36 = 0.0139
(concentration?) per month.
awright ... so what's 'dangerous'?? below 10 percent? that would
be ..0.05 concentration?
well, who knows ... so let's pick something. say 20 percent or
0.1 concentration.
so how long will that take to get down to 20 percent? 100-20 =
80, 80/2.78 = 28.8 months or say 29 months. hmmm. just about two
years. how bout that. :)

now, at 29 months, you add what ... 1/29th of the 18 liters? if i
read you correctly.
so that's also 1/29th of the 9 liters of pure antifreeze ... so
we added what? 0.31 liters of antifreeze?
so how do we figure the new concentration?
if we have 18 liters that is down to 20 percent (instead of 100
percent), that means that instead of 9 liters of pure antifreeze,
we have only the equivalent of 0.2 x 9 or 1.8 liters of pure
antifreeze.
if we remove the 1/29th of 18 liters (0.62 liters), we should
still have 17.38 liters at the same 20 percent.
now we add back 0.62 liters but at 100 percent.
so we had 18 liters at 20 percent, or 1.8 liters of pure
antifreeze. we take away 1/29th of the 18 liters and that means
1/29th of the 1.8 liters that are left ... or 0.062 liters of
pure antifreeze. leaving 1.8-0.062 = 1.738 liters left in the 20
percent concentration.
then we add back 0.31 liters. so 1.738 + 0.31 = 2.048 liters of
pure antifreeze in a 18 liters system (remember we added back the
whole 1/29th).

so we went from 1.8 liters (20 percent) to 2.048 liters ... and
that should be 22.76 percent (if i did that right). not a whole
lot of increase... but it did go back up above 'dangerous' (what
we defined 20 percent as).
but next month, we do the same thing ... and if we are losing
2.78 percent each month, we're right back where we started: at
the dangerous level. acutally, a tiny bit below it.

is this right?

argh, that makes my head hurt. :)
anyway, i kinda don't think it's a good idea. just because! ;)

joel