[ROVERNET - UK] Coolant choice
vern at inkspotco.com
Tue May 30 20:55:32 BST 2006
Here is an article I wrote a couple of months ago
for the Roverview, about coolants.
Most car owners, when asked to describe the parts
of the cooling system of their car, list the
radiator, water pump and hoses, and think of the
coolant itself as just the stuff in the radiator.
In fact, the most important part of the cooling
system is the coolant itself. Using the wrong
fluid or not maintaining the quality of the fluid
will lead to greater grief than a soft hose or a
leak in the radiator will (unless you are miles
from anywhere, in the desert, when the leak is
discovered, that is).
There are three tasks that any coolant must
perform: First, it must act as an efficient
medium to transfer heat from the engine. Second,
the coolant must control corrosion and sediment
within the cooling system. And finally, the
coolant must remain liquid at the environmental
temperatures the engine operates in, which in our
context means it shouldn't freeze.
All modern cars use glycol/water mixtures as
coolant. This is more to satisfy the third
requirement of a coolant than the first two
requirements. And it does do that well, with a
50/50 ethylene glycol/water mix not freezing
until -37°C (-35°F).
Until recently, ethylene glycols has been the
glycol of choice. Concerns about its toxicity and
a sweet flavour that encourages animals and
children to sample it have led to more use of
propylene glycols, which are lower in toxicity
but more importantly, does not have the sweet
flavour. However, it does not provide quite as
good protection, as a 50/50 mixture freezes at
While the glycol coolants protect against
freezing, they are relatively poor at the first
task of a coolant, transferring heat. In fact,
water is a superior coolant for two reasons. Most
importantly, it has twice the heat capacity of
the glycols. That means that it takes twice as
much heat to raise the same quantity of water 10°
as the same quantity of a pure glycol. The second
reason is that water is a quarter the viscosity
of a typical glycol. The lower viscosity helps
heat transfer as the hot water mixes more readily
with the cooler water away from the engine
surfaces, moving heat away from the engine metal.
Water freezes though, and so is impractical as a
year-round coolant in our cars.
Water is also poor at corrosion and sediment
control. Water can contain dissolved minerals,
and its solvent nature means that many corrosion
processes are enabled in a water bath. The
glycols are pure materials so have no dissolved
minerals, but as they are mixed with water in
use, must have corrosion protection chemicals
How this applies to our collector cars is explored next.
Personally, I use 100% water during the warm
months of the year and a glycol mixture just
sufficient to protect to the coldest weather I
see during the winter in my daily driver P6.
Someone who only uses their car during the warmer
months could do the same, but simply drain the
system for the winter. Mind you, many heaters
cannot be completely drained and an empty
radiator raises the specter of forgetting to
refill come spring. The twice-yearly change of
coolant also performs the important task of
replacing the anti-corrosives in the system.
But wait you say, didn't you just write that
water fails to perform any anti-corrosion duties
by itself? That's true. I've been keeping
something from you.
First, I use only distilled water. Distilled
water (not deionized water, which still contains
minerals) is free from dissolved minerals,
solving a good part of the problem.
Second, I add an product from Red Line Synthetic
Oils, called Waterwetter. We'll get to the
"waterwetter" later, here the point is that this
product has all the anti-corrosive additives you
would normally find in an glycol coolant.
Okay, why "waterwetter"? The main purpose of the
product is not corrosion control, it to act as a
surfactant, which is a substance that reduces
surface tension in a liquid. Surface tension is
the force that makes a drop of water bead on a
waxed surface. If surface tension is reduced, the
bead collapses and wets the surface better.
Hence, the "waterwetter" name.
This is an important effect and it works just as
well with glycol coolants as water. It increases
the ability of a coolant to transfer heat from
the engine this way: Heat from the engine causes
the microscopic layer of coolant next to the
engine surface to boil. This vapour then
condenses into the next layer of coolant
transfering the heat. Lower surface tension
allows the vapour to condense more readily into
the coolant, increasing efficiency.
It is a win for everybody. If you use regular
glycol coolant mixes in your car, Waterwetter
will improve the performance of your coolant
close to that of pure water. Using it with pure
water will result in even greater performance.
Your car will have a greater ability to endure
those long climbs in the hot sun without
overheating and will generally run cooler all the
Never forget, however, that maintaining that
performance means regular coolant changes to
renew the anti-corrosion properties of whatever
coolant you chose to use.
>I did a bit of searching on coolant choice this
>weekend, It's the first really hot weekend in
>NY, and the temp gauge on my 2000TC was just at
>the top of the green section and would
>occaisionnally cross the line into the low red.
>I think re-coring the radiator may be on the
>cards. The coolant quite clean, and I think the
>engine had been flushed before I bought the car
>Anyway, apparently the antifreeze does stop
>corrosion in the engine, but also inhibits
>thermal conductivity (so I was wrong with my
>last email on this). So it doesn't cool as
>efficiantly as pure water.
>I did find a product called 'water wetter' from
>redline oils that's meant to improve the wetting
>abilies of coolant and thereby improve cooling
>by up to 30 deg F. I'll add some to the coolant
>in my car and tell you if anything improves. Has
>anyone else used this or a similar product? did
>it work for you?
>That's about it apart from the fact that I got
>my NOS carbs' fitted this weekend and what a
>difference it made. I kept thinking the engine
>had stalled when pulling up at the lights, and
>I'm not creating my own personal hole in the
>ozone layer any more.
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Vern Klukas I'm a little . . .
Inkspot Type & Design
vern at inkspotco.com
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