Copy & paste, interesting article..
Top it up with green? Or orange? Which antifreeze?
By Patrick Bedard
It's 2002. Do you know where your corrosion inhibitors are?
Some folks take the yawn approach to what goes on between consenting
chemicals in the ****** privacy of a car's cooling system. Not me. And
now my sensitivities have been further heightened. It was the weighty
check I wrote to a welder for filling in some missing places in a
cylinder head that did it. Funny how much aluminum went AWOL in the
30-some years since that engine left the factory, enough to leave
gaskets hanging in midair.
Funny? I laughed all the way to Coolant College. David Turcotte is the
technical director for Zerex, the line of coolant products from
Valvoline. He's a good-natured guy with "Dr." in front of his name. That
means he knows everything. So I pestered him until he sent me a package
of tech papers about antifreeze and agreed to hold still for follow-up
questions.
Modern antifreeze, he says, is 96-percent ethylene glycol, which
provides the freeze protection, and four-percent additives. When you
dilute that blend 50-50 with water, as the makers intend, you push down
the freeze point to minus 34 degrees Fahrenheit. In normal
circumstances, you also gain corrosion resistance . . . for a while. The
freeze protection is permanent, but the additives are consumed in
battle, so to speak.
About half the additive is made of buffers to control acid buildup; the
other half is corrosion inhibitors to protect metals.
Perhaps the battle is already going badly in your car. A sticking
thermostat can be an early indicator. The next stage: As detritus
migrates through the system, it settles in the most confined spaces. If
your heater blows cold, uh-oh.
I was hoping that technology, as it marches relentlessly toward
obsoleting everything I own, might also have created new antifreeze
formulas that would bring forbearance and frustration to the chemicals
frolicking under my aging radiator caps.
Of course, no doctor writes the prescription before he considers the
patient. The "old" antifreeze technology started in the '60s, improved
in the '70s, Turcotte says, and was superseded in cars of the '90s by
two new technologies. It turns out that an antifreeze transplant into
older cars will work fine with one of the new types; the other will
probably kill the patient.
The old technology, a.k.a. "conventional," a.k.a. "inorganic," is green
in color. Most of what you see on the shelves at Wal-Mart and AutoZone
is conventional, including the yellow bottles of Prestone and the white
bottles of Zerex.
One of the new types is "organic acid technology," or OAT. It's orange.
General Motors pioneered this chemistry starting with 1996 models in the
U.S. and using the name Dex-Cool. Ford changed a few models to OAT, then
backed away from it. VW, Audi, and Porsche are OAT users, too, but most
others have resisted.
Instead of OAT, most new cars now use a "hybrid" antifreeze that's
formulated with both OAT and the silicate inhibitors from green
(Japanese hybrids have different inhibitors). It comes in too many
colors to pretend this type is color-coded. Interestingly, Turcotte says
that as the materials improve for the white plastic overflow bottles of
new cars, and they become less yellowing over time, automakers are
becoming more venturesome in choosing coolant colors.
The promise of OAT is long-life corrosion protection, on the order of
six years/ 100,000 miles for the initial fill instead of the two
years/50,000 miles that was typical with the old green stuff. The GM
Dex-Cool formula works fine in systems designed for it. But it eats
old-style radiators with lead solder, and the inhibitors work too slowly
to protect against the sort of corrosion that happens so fast it
actually erodes metal—for example, the cavitation likely in the
imperfectly designed water pumps of older cars.
"Cars born with green coolant shouldn't be changed to orange," Turcotte
advises. It's also a bad idea to mix the two, although the result
doesn't immediately turn into witches' brew.
Coolant technology is driven by the makers of new cars to solve new-car
problems (same with motor oil.) By the time a car gets old enough to be
interesting to a collector, the latest antifreeze blends have moved on
to protecting newer alloys and gasket materials. Fortunately, the
aftermarket lives by catering to older cars.
As for those aging characters we're keeping around as playmates, no
matter what antifreeze we choose, and no matter how often we replace it,
Turcotte says the best medicine is to play often. Coolant down in narrow
crevices can become isolated, then overwhelmed by corrosion. Once it
starts, the best you can hope for is a stalemate. You can't undo
corrosion. To keep protection active in all the crannies, the system
needs to be heated and circulated every 30 days, he advises. (Hey, Ed.,
more play days, please.)
Obvious question: What about the water we mix in? He says modern
coolants are designed to work with "reasonable" levels of hardness and
chlorides in tap water. But magnesium and calcium, the hardness ions,
unquestionably contribute to scale and deposits, which hurt cooling
efficiency. And chlorides are corrosive. He says distilled water gets
rid of all the worries. (It was 58 cents a gallon at my local Wal-Mart
yesterday.) Or you can buy "predilute" coolant already mixed and ready
to go.
In my vision of purgatory, I'll be sentenced to changing antifreeze in
all my cars, day after day, and some archangel with white gloves and a
test tube will be checking the color of my flush water for contaminates.
I have to keep flushing until he can't tell the drain-out from the
distilled he carries in another tube as the control.
Here in this life, I've always changed my coolant. I'm one of those guys
who agonize over details. So the job takes a full afternoon for each
car. I drain everything that comes out through the *****, then top up
with clear water, warm the engine, and run the heater to circulate
fully, then drain again. Repeat at least three times.
What to do with the drainings? I called the local pollution controllers.
Antifreeze? Their book had no mention of it. After thinking a bit,
however, they told me to put it out back in buckets and let it
evaporate. Rocks evaporate at about the same speed.
Old coolant "hanging up" in the system is a real concern, Turcotte says.
But he also knows that nobody gets it all out.
"We've done tests," Turcotte says. "If you open a drain [******] or drop a
bottom hose, you might get 50 to 60 percent out. The best machines, the
new ones going into Valvoline quick-oil-change shops, get 80 to 85
percent." This is a manageable level of contamination, as long as the
new antifreeze doesn't fight with the old.
Next month: The doctor writes a few prescriptions.
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