1. According to ASTM D11777, the freeze point of a 10% solution is 26 deg

F.

 I
 > >>     dunno where Thomas Parkes parks [ok,ok, no more puns] his

aircraft,

but this
 > >>     might be a big problem for him in the winter.
 > >>  2. Furthermore, that same test indicates that the "slush point"

(where

ice
 > >>     crystals form in the solution) can be as 30 degrees warmer.

While

obviously
 > >>     no ice crystals are going to be forming at 56 deg F, it is likely
that the
 > >>     coolant will begin to freeze at 32 deg F.  What most people don't
know about
 > >>     the "freeze point" of antifreeze is that it is set in reference

to

a hard
 > >>     freeze of the material (effectively the "copper pipe burst"
temperature).
 > >>     Prior to this hard freeze, however, the solution gradually turns
into a hard
 > >>     slush that can easily damage more delicate parts.
 > >>  3. Antifreeze manufacturers formulate their products to be used in

the

40% to 60%
 > >>     solution range.  This is because of the additive package.  It has
all sorts of
 > >>     useful things in it like cavitation protectant (nitrite),

aluminum

corrosion
 > >>     inhibitors (silicates), ferrous metals corrosion inhibitors (
nitrate), etc.
 > >>     If one greatly dilutes the antifreeze, there may not be enough of
the additive
 > >>     in the coolant to do the job.  For example, ASTM D2809 specifies
the
 > >>     cavitation and erosion corrosion test for engine water pumps.

Most

(all?)
 > >>     automotive antifreeze products meet this standard when used in

the

40% to 60%
 > >>     dilution.  Over dilute, however, and the package may not protect
sufficiently,
 > >>     which could lead to premature failure of the water pump.


 > >>Were I Thomas, I'd use a 40% automotive antifreeze solution using *
distilled* 60%
 > >>water, keep the 13 p.s.i. pressure cap, calibrate the temperature

sender

using a
 > >>pot of boiling distilled water, locate the temperature sender as close
to the block
 > >>outlet as practical, leave the alarm setpoint at 220 deg F, and sleep
well.
 > >>
 > >>Russell Kent

     On the other hand, assuming one is bright enough to protect the system
from freezing solid, The higher the glycol content the smaller the radiator
in terms of effectiveness. In practical terms, if I am having overheating
problems, my first move is to dump the glycol and install pure water. I
cannot run the 10% mix above 95 degrees ambient. Only water. While a glycol
mix does raise the boiling temp, it also guarantees that you will need a
higher boiling temp, because glycol doesn't conduct heat very well.

     If you need the higher boiling temp, run a higher system pressure. If
you are doing things like this to operate on anything but the very hottest
days, maybe more cooling capacity is in order. The ideal would be that you
can run the recommended glycol/water mixture and have it cool just fine with
the lashup you have now. If you can run it flat out on a hot day without
glycol but not with glycol, then the system is close to ideal, and a small
added capacity is required. Additional attention to ducting, airflow,
shielding and the like. I would not go above 22 pounds for fear that the
radiator tubes my swell and loose contact with the fin material. Evaporator
cores can go over 100 PSI. However some aftermarket radiators have tubes as
deep as 1 1/2" and are vulnerable. Keep in mind that temperatures above 160
degrees is cutting into power output on NA engines and continuous operation
above 220 is begging for engine damage.

     My 16 pound Stant lever cap has been in continuous service since 1980.
It is looking tired and the rubber gasket is not original, but it works fine.
Those additives are just fine for cars I guess. But I have been brutalizing
Mazda rotary engines since 1980 and the only evidence of corrosion I have
found to date is in blown engines that have been gifted to me and have been
left with water or coolant in them in small quantities, probably for years in
some cases. The few I get with any amount of coolant left in them seem to be
fine. I think the long time it takes to evaporate the coolant lets oxygen
into the surface film and keeps it there a very long time. Some times the
cast iron gets too pitted to use, but not any aluminum yet. That is to say
the housings I throw away are grooved to death but seldom corroded to any
great extent.

     If there were some room available, I would think about a pancake fan for
climbout on the very hottest days.

Lynn E. Hanover

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