Date:         Sun, 23 Dec 2001 18:55:48 -0800
Reply-To:     Alistair Bell <albell@UVIC.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Alistair Bell <albell@UVIC.CA>
Subject:      FWIW: coolant article (v.long)
Content-type: text/plain; charset="ISO-8859-1"

some interesting points made here.

(http://www.babcox.com/editorial/us/us60024.htm)

Alistair

New Coolant Chemistry, Larry Carley, Underhood Service, June 2000

Cooling chemistry has undergone some significant changes in recent years.
The familiar green antifreeze that has long been used in most vehicles is
being replaced with a spectrum of not-so-familiar antifreezes in new cars
and light trucks that range in color from red to orange to pink to blue.
When you open a radiator cap today, youıre never quite sure what youıre
going to find. But from a service standpoint, itıs essential to know what
type of antifreeze is in the system so you can add a compatible coolant, or
replace it with one that provides equivalent or better protection.

Letıs start with a look at the basic ingredients in antifreeze before we get
to the various additive packages that make them different.

Ethylene Glycol
Ethylene glycol (EG) has been the main ingredient in almost all automotive
antifreezes for many years, and will continue to be for the foreseeable
future. Straight ethylene glycol freezes at about 8° F, boils at 330° F, and
carries heat about 15% less efficiently than water. But when mixed in equal
parts with water, it creates a coolant well suited to year-round driving.

The recommended 50/50 mixture of EG and water provides freezing protection
down to -34° F and boilover protection to 265° F in a radiator with a 15 psi
cap. If the proportion of antifreeze to water is increased to 70% EG and 30%
water, the freezing point drops to -84° F and the boiling temperature goes
up to 276° F. Mixtures greater than 70/30 are not recommended because the
coolantıs ability to carry heat declines as the proportion of antifreeze
increases.

Straight EG antifreeze should never be used in an engine because it may
allow the engine to overheat. Likewise, straight water should never be used
because it provides no freezing, boiling or corrosion protection.

Propylene Glycol
Another base ingredient that is used in place of EG in some aftermarket
antifreezes (Prestone "LowTox" and Safe Brands "Sierra" antifreeze) today is
propylene glycol (PG). The coolantıs thermal characteristics are similar to
those for EG: a 50/50 mixture of PG and water provides freezing protection
down to -26° and boilover protection to 256°. If the coolant mixture is
increased to 60/40, freezing protection goes down to -54°F. The main
advantage of PG compared to EG, however, is that it is considered "nontoxic"
to animals. That doesnıt mean it is "safe" to drink, but it greatly reduces
the risk of poisoning a pet.

Pure PG boils at 370° F and provides freezing protection down to -70° F, so
it is sometimes used straight without any water at all as a coolant in
racing applications. Running PG straight provides better cooling because
there is no water to vaporize in hot areas of the cylinder head. This also
allows the use of very low pressure or even no pressure cooling systems.

PG and EG are both compatible antifreezes and can be intermixed without
affecting cooling performance. But intermixing the two different antifreezes
is not recommended because doing so defeats the reduced toxicity advantages
of PG. Also, if a vehicleıs cooling system is filled with an extended-life
EG coolant, adding PG (which is not currently formulated for extended
service) will reduce the service life of the coolant mixture to that of a
conventional green coolant.

Intermixing PG and EG antifreeze also makes it impossible to get an accurate
indication of the coolantıs strength if youıre using a hydrometer to check
coolant concentration. The specific gravity of EG and PG are different, so a
mixture of the two will usually indicate a lower freezing point than the
coolant actually provides.

The best way to determine the concentration of PG in uncontaminated coolant
(no EG present) is to use a refractometer; the specific gravity of PG
increases up to about a 70% concentration, then falls off. Consequently, a
100% PG solution will read the same as a 45% solution on a hydrometer.

PG is approved as an acceptable replacement coolant by General Motors and
others, but if making a change, itıs important to remove all of the old EG
coolant before adding PG to the system.

Corrosion Inhibitors
Because coolant is in constant contact with the metal parts of the engine
and radiator, some type of corrosion inhibitors must be used in the
antifreeze to protect all metal surfaces from electrolysis. That includes
cast iron, steel, aluminum, brass, copper and lead solder.

Most conventional antifreezes formulated for the North American market,
whether green or yellow in color, contain inorganic salts of borate,
phosphate and silicate to prevent rust and corrosion. The additives create
an alkaline coolant mixture that typically tests at about 10.5 on a pH
scale. The silicates form a protective coating on metal surfaces and are
especially good at protecting aluminum.

To ensure that the coolant remains alkaline for a reasonable length of time,
there must be enough corrosion inhibitor to neutralize the acids formed from
glycol degradation that occur over time. This neutralizing capability is
called "reserve alkalinity," and it varies depending on the type and
quantity of additives used in a particular brand of antifreeze.

Heat, dissolved oxygen, minerals in the water and corrosion inhibitor
reactions at the metal surface gradually "use up" the corrosion inhibitors,
and, once depleted, the coolant becomes acidic and corrosion accelerates.
The secret to preventing internal corrosion, therefore, is to change the
coolant before all the reserve alkalinity has been used up.

Periodic coolant changes are especially important with todayıs bimetal
engines and aluminum radiators and heater cores because the different metals
create a miniature battery cell that promotes electrolytic corrosion.
Aluminum becomes the sacrificial anode, iron the cathode, with the coolant
serving as the charge-carrying electrolyte. The higher the percentage of
dissolved minerals and salts in the coolant, the better it conducts
electricity and the faster the aluminum is eaten away. As long as the
corrosion inhibitors are working, the process is held in check. But once
theyıre used up, corrosion starts to eat away. The most vulnerable
components are usually the thinnest, which include the radiator and heater
core.

Other problems can also accelerate the breakdown of the coolant. An exhaust
leak into the cooling system through a cracked head or leaky gasket will
quickly destroy reserve alkalinity in the coolant because oxygen reacts with
the additives in the antifreeze. If an engine has a leaky head gasket, donıt
reuse the old antifreeze when the gasket is replaced.

The amount of additive needed to protect the cooling system isnıt much, only
about 2-3% of the total liquid in the jug. This is usually enough to protect
for at least two years or 30,000 miles in most vehicle applications - or
even longer if the antifreeze is mixed with relatively pure water (distilled
or deionized). Some say ordinary antifreeze can go as long as five years or
100,000 miles before the corrosion inhibitors are fully depleted - provided
pure water is used to fill the system, the cooling system was relatively
clean when filled (no accumulated rust or scale), and the coolant level is
kept full (no air entrapment).

Hard water that contains high amounts of calcium and magnesium can react
with phosphates in the additive package to form sediment and scale. Thatıs
why the European vehicle manufacturers use antifreezes that contain no
phosphates (hard water is common in Europe). European antifreeze may be dyed
blue, yellow (Mercedes) or pink (VW and Audi). Tap water in North America
also contains calcium, but isnıt as hard as European tap water so phosphates
are considered okay to use here.

Under no circumstances should "softened" water be used in a cooling system
because softened water substitutes sodium (salt) for calcium. Sodium is very
corrosive to all metal surfaces and undermines the corrosion-inhibiting
abilities of the additives.

The Japanese and other Asian vehicle manufacturers, by comparison, prefer an
additive package that contains phosphates and other inhibitors but no or low
silicates. Japanese coolants may be dyed red, but some of the newer blends
are dyed green.

According to the aftermarket antifreeze suppliers we interviewed, using a
typical green antifreeze formulated for North American domestic vehicles in
European or Japanese vehicles should cause no problems. The basic metallurgy
is the same so the degree of protection provided should be the same: two
years or 30,000 miles.

OAT Technology
The latest corrosion-inhibiting additives are based on a different chemistry
called "Organic Acid Technology" (OAT). Antifreezes with OAT corrosion
inhibitors contain organic acid salts of mono- and dicarboxylic acids such
as sebasic and octanoic acids, plus tolytriazole. The coolant is less
alkaline and protects with a pH reading of only about 8.3. Brands with the
OAT additive package include Texaco/Havolineıs "Dex-Cool" and Prestoneıs
"Extended Life 5/150" antifreeze. OAT coolants contain orange dye to
distinguish them from other coolants with conventional additive packages.

The main advantage of OAT technology is extended service life: up to five
years or 150,000 miles. But to achieve this length of service, the OAT
coolant must not be intermixed with any other type of antifreeze. If the
system is topped off with ordinary green antifreeze, the corrosion
protection will be reduced to that of a conventional coolant, say the
coolant manufacturers.

General Motors was the first domestic vehicle manufacturer to make the
switch to OAT coolants, starting in 1995. Since 1996, all new GM cars and
light trucks have been factory-filled with orange Dex-Cool coolant. GM says
Dex-Cool can be used in older vehicles provided the cooling system is first
flushed to remove all traces of conventional coolant. But people have said
OAT-based coolants do not provide adequate protection for vehicles with
lead-soldered copper/brass radiators - a charge the makers of OAT antifreeze
say is not true. Texaco/Havoline and Prestone both say their products meet
or exceed the ASTM D-2570 standards for corrosion protection.

There has been some controversy regarding the use of OAT coolants because of
sludging problems GM experienced in some 4.3L S10 truck engines. GM service
bulletin #99-06-02-012 says the sludging problem is caused by air pockets in
the cooling system from failing to maintain the coolant level or not getting
all the air out the system when refilling the cooling system. GMıs fix for
the condition is not to switch back to a conventional coolant (which some
people advocate), but to flush the system repeatedly until all the brown
sludge has been removed. The system can then be refilled a 50/50 mix of
Dex-Cool and clean water.

Despite the problems with the 4.3L truck application, the use of OAT
antifreeze is expected to grow. DaimlerChrysler introduced its own
extended-service OAT hybrid coolant for passenger cars in 1998. Unlike
Dex-Cool, the DaimlerChrysler coolant contains silicates for extra aluminum
protection. DaimlerChrysler, however, does not recommend using their OAT
hybrid coolant in older vehicles.

Ford in North America is still using conventional additives in its
antifreeze, with the exception of the ı99 and up Mercury Cougar, which now
uses an OAT coolant. But Ford of Europe has switched over to OAT antifreeze
for many of its vehicles. OAT has also been approved by truck manufacturers
including Navistar, MAC and Caterpillar.

Coolant Checks
One problem we have in the aftermarket is that we have no way of knowing
what kind of antifreeze is in a customerıs cooling system when it comes into
the shop. It may be the factory-fill coolant, it may be an aftermarket
coolant, it might be a propylene glycol coolant, or it might be a mixture of
several different types of coolants. If you donıt keep this in mind, a
simple coolant check with a hydrometer may give you a false indication of
the strength of the coolant. A refractometer is a better tool to use because
it doesnıt measure specific gravity but how the liquid bends light.

Chemical test strips are available to check both the concentration and
condition of the coolant, too. But test strips designed for conventional
green coolants wonıt give an accurate indication of the coolantıs condition
if used with an OAT type of coolant.

A special test kit marketed by Analyst Inc. (877-839-2435) can give a
pass/fail indication if a vehicle with Dex-Cool coolant has been
contaminated by another type of coolant. If it contains 15% or more of
something else, it fails the test. The kit (P/N LS-TST-STRIP) sells for
$24.99 and includes 10 test strips.

Coolant Service
Though most coolant service consists of flush and fill, ethylene glycol
coolants can also be recycled using the proper equipment (see October 1999,
Underhood Service). Recycling has obvious environmental benefits, and can be
a source of additional profits for your shop. EG coolants with OAT additives
can also be recycled, but the aftermarket additives currently available only
return the coolant to a standard two-year/30,000 mile silicated coolant.

When refilling a late model GM vehicle that was factory-filled with
Dex-Cool, you have to decide what type of coolant to use. According to GM,
Dex-Cool is the only acceptable coolant. But once the vehicle is out of
warranty, thereıs no reason why you canıt use another brand of OAT coolant
or a conventional EG or PG coolant, say the makers of these products.

The same goes for using an OAT coolant in an older vehicle that contains a
conventional green type of coolant. If the system is thoroughly flushed, you
can give your customer the extended service benefits that an OAT coolant
provides. OAT coolants can also be used to refill European and Asia
vehicles, provided the system is first flushed to remove all traces of the
old coolant.

The National Automobile Radiator Service Association (NARSA), however, is
more cautious about the use of OAT coolants. NARSA says OAT coolant should
not be used in any Ford product (except the ı99 Cougar) or Chrysler because
there is a risk of water pump cavitation erosion. GM reportedly redesigned
its water pumps to eliminate cavitation erosion.

Another question that comes up is one concerning the compatibility of
Dex-Cool with other OAT coolants. Texaco/Havoline, the manufacturer of
Dex-Cool, says their additive package is not the same as one in Prestone,
and that other brands do not meet GMıs Dex-Cool GM-62277M requirements.
Prestone, on the other hand, insists their Extended Life 5/150 OAT-based
product is compatible with Dex-Cool and meets the GM-62277M requirements. Go
figure.

Regardless of what type of coolant is used to refill a cooling system, the
system should be cleaned if sediment, rust or scale are present. Also, the
system should be pressure tested to make sure there are no leaks. And donıt
forget to pressure test the radiator cap, and inspect the belts and hoses,
too.

Refilling some of todayıs vehicles can be tricky if the heater core or other
hoses are higher than the radiator cap. If the system has bleeder valves,
use them. If it doesnıt it may be necessary to jack up the front of the
vehicle so the radiator cap is the highest point in the system.

Keeping Coolant Clean

A survey of ASE-certified automotive technicians throughout the nation
determined that coolant is the second most neglected vehicle maintenance
item. Coolant should be checked for both strength and also pH level at each
service. To check the pH level, you should use a chemically treated test
strip, which can be purchased at most parts stores.

The average pH level range of typical coolant is around 10.5. When diluted
with water, it drops to 8.5 to 9. A pH level at 7 or lower can lead to both
excessive corrosion and electrostatic discharge (ESD). With ESD, the PCM can
receive false readings from the electronic coolant temperature sensor, which
can lead to poor fuel economy and the setting off of diagnostic trouble
codes. With a low pH level, the coolant becomes acidic, which can cause
hose, radiator and water pump failures.

So the bottom line is that if coolant is contaminated or the additives are
depleted, flush the system. The use of low or no silicate coolant at a 50/50
ratio is best. You and your customer will be satisfied with a job well done.

Also, radiator caps play an important role on automotive cooling systems.
They can lead to radiator or water pump seal damage. The job of the cap is
to hold pressure on the system, which raises the boiling point of the
coolant and prevents steam bubbles from forming inside the cooling system.

Caps should be pressure tested each time the system is serviced. Most caps
will range from 4 psi to 18 psi.

When testing the cap, it should hold pressure for two minutes. If it
doesnıt, the cap should be replaced. The condition of the gasket in the cap
also should be inspected for swelling or tears that could lead to coolant
loss and engine overheating.

Courtesy Airtex Automotive Division