[ROVERNET - UK] Coolant choice

Vern Klukas 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 
-32°C (-26°F).
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.  


>Hi Ali,
>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 
>last October.
>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.
>Take care,
>rovernet mailing list
>rovernet at lyris.ccdata.com
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Vern Klukas                             I'm a little . . .
Inkspot Type & Design
vern at inkspotco.com

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