Unofficial BMW

Unofficial BMW

Google Search

What's New

Search (Google!!)









Used Cars




In Association with

Home E12 E24 E28 E30 E34 E36 Z3 E39 E46 X5/E53 ALL
Ron Stygar Carl Buckland Dale Beuning Forums Help

Unofficial BMW Nav Map

From digest.v5.n26 Wed Jul 24 16:01:44 1996
From: henri baccouche <>
Date: Wed, 24 Jul 1996 12:42:52 +0000
Subject: antifreeze confusion

I stumbled across this info: Thanks to Jan Vandenbrand <>

Archive-name: autos/vw/technical-faq
Rec-autos-vw-archive-name: technical-faq

Q: I want to flush my cooling system. Where can I get phosphate free coolant

other than at the overpriced dealer prices?

  1. 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 [] Aluminum oxide in solution

forms a black paste that makes a real mess, this will be visible inside the

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 away....

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 which

has been boiled in a pot so that the calcium is left there and cannot harm

     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 safe).

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.

From Jens:
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 effectiveness.

See also the archive file "Anti_Freeze" for additional details, and the performance faq on improving heat transfer.

Copyright Notice (c) -- 1994 - 1996:
All Rights Reserved

The information contained here is collectively copyrighted by the authors. The right to reproduce this is hereby given, provided it is copied intact, with the copyright notice inclusive. However, the authors explicitly prohibit selling this document, any of its parts, or any document which contains parts of this document. (Inspired from ;->)

Unofficial Homepages: [Home] [E12] [E24] [E28] [E30] [E34] [E36] [Z3] [E39] [E46] [X5/E53] [ALL] [ Help ]