From digest.v5.n26 Wed Jul 24 16:01:44 1996
From: henri baccouche <henri_at_powerplant.BarePower.net>
Date: Wed, 24 Jul 1996 12:42:52 +0000
Subject: antifreeze confusion
I stumbled across this info: Thanks to Jan Vandenbrand <jan_at_ug.eds.com>
Q: I want to flush my cooling system. Where can I get phosphate free coolant
other than at the overpriced dealer prices?
- Phosphates corrode aluminum (all VW heads) through an electrochemical
reaction with the cast iron block, which is why VW recommends to use
phosphate free coolants.
According to [scornelius_at_ws11.iac.honeywell.com] Aluminum oxide in
forms a black paste that makes a real mess, this will be visible inside
coolant bottle once the corrosion process has started (I've seen this in a
custom street rod). So if you see a used VW with this condition, run
According to [Vincent Yeung] who called Prestone:
Phosphate free anti-freeze is necessary in Europe because of
the very hard water they have there. Somehow the phosphate in
ordinary anti-freeze will react with the minerals in the hard
water. However, he said the water in North America is not as hard
and he knew a lot of VW with aluminum radiator have no problem
using ordinary anti-freeze with tap water.
In the US market, all the popular brands until recently (Prestone, Zerex)
contain phosphate in a buffered solution which keeps the phosphates in the
coolant from ionizing (so they claim), at least for a while.
I have used Prestone without seemingly ill effects, but if you want to be
100% sure, not void warrantee, use VW's coolant. Furthermore, mix with
DISTILLED water, NOT tap water. Also do not mix coolants of different
types. Flush the system before you change!
A counter point from Jens:
It is not such a good idea to use destilled water, best is tap water
has been boiled in a pot so that the calcium is left there and cannot
your cooling system. Destilled water is too aggressive.
[Jan]: I checked with some chemists on alt.chem and they cannot see why
it would be too aggressive.
Newer coolants by Prestone (4/60), Arctic, Quaker State and
BASF's Zerex Extreme are phosphate free,
and are sold with different labels as to clearly identify the new product.
They are selling these phosphate free products for environmental reasons!
They all advertise around a 4 year-50/60k miles life expectancy.
Whether that's purely marketing (the stuff costs more) or a significant
difference over the original formulations (that probably will last that
long as well) remains unknown.
Unverified claims: Texaco's coolant is also Phos free.
Whether these have any long term harmfull side effects (probably not)
still remains to be seen (these products were introduce in 93 in the US).
Note that VW's coolant is also made by BASF, but seems to be
as slightly different formulation than their commercial Zerex product.
According to BASF, Zerex Extreme has been approved to be used in
VW, BMW, MB, Audi, Saab, and Volvo.
Sierra's new anti-freeze is based on Propylene Glycol (environmentally
Propylene Glycol is used as a "light" oil substitute in foods and is
therefore not as deadly as Ethylene Glycol.
See also below for more details.
ND has the following to say about Sierra:
"Total marketing !! This is just another coolant with a different formula
and since most all coolant is recycled now the enviro aspect is mute.
This stuff will not work any better than any other coolant. Almost all
coolant nowadays is ok to use in your VW. Just make sure it was designed
for Aluminum heads which is almost all of them now."
Another thing to note is that VW claims that its original coolant
does not have to be renewed every two years like Prestone.
The reason they give that coolants like Prestone have sacrificing
chemicals that prevent corrosion for a certain period.
VW claims that their coolant does not have any sacrificing
chemicals and therefore does not wear out.
Personally, I don't think this is entirely true, and as a precaution,
I change the coolant of it turns color or every couple of years.
In some of the cars I have owned they coolant looked perfectly
fine, in others it turned reddish brown after a couple of months.
No precaution necessary. There are people (like me) who used the same
coolant for more than 10 years without problems. CAUTION: After changing
metal engine parts (thermostat housing, cyl. head) you should always
change the coolant to protect the new parts with the anti corrosion
of the coolant. The anti corrosion worked up by this process and the
old coolant has not enough anti corrosion to work on the new parts.
Also, change anti corrosion after you have changed a defective cyl.
head sealing (because it may have let exaust gas into the coolant which
is chemically "destroyed" by the gas).
Best coolant in Europe seems to be Glysantin by BASF, there is nobody
who would use anything different (except all Shell-, Texaco-, BP-,
...-stations who sell their own stuff, of course). Glysantin protects
the aluminum cylinder head of corrosion, it builds a thin film on all
parts of the cooling system to protect them, it makes the coolant pump
last longer (even made my old loud "non-Glysantin experienced" pump
go quiet) and does not harm the environment (at least not more than
other coolants). And: when Glysantin changed its colour from brown to
green, VW's coolant colour changed from brown to green, too ;-).
This is not an endorsement of either products. I have no idea as to their
See also the archive file "Anti_Freeze" for additional details, and the
performance faq on improving heat transfer.
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