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Date:         Mon, 11 Sep 95 12:20:27 CDT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Joel Walker <JWALKER@ua1vm.ua.edu>
Subject:      Re: Sierra Propylene Glycol Coolant?

On Mon, 11 Sep 95 10:55:38 CDT Mr.Roger Bowman said: >I really don't understand the need to keep the phosphates out of the system,

this is what i dug up a while back on the subject:

COOLANT/ANTI-FREEZE: Recommended coolant/anti-freeze: Autobahn ZVW-237-104 antifreeze & summer coolant Phosphate free formula for use in Volkswagen & Audi water cooled vehicles Ethylene Glycol based, Phosphate free recommended mixture: not less than 40 percent coolant, not more than 60 percent. sold at VW dealers only. manufactured by BASF Questions? Call 1-800-669-2273 BASF Customer Service: 1-800-445-4134 BASF Marketing Service: 1-800-367-9865 BASF Technical Service: 1-800-521-9100 Info from Marketing Service: <as of 03/94> BASF makes a 'generic' brand of GUARANTEED Phosphate Free coolant called ZEREX EXTREME 450. It has been approved by VW, BMW, MB, Audi, Saab, and Volvo. It is also GUARANTEED for four (4) years and 50,000 miles. They said you CANNOT mix this with any other coolant; you must flush the system and fill with the new coolant/water mix. Info from Tech Svc: <as of 03/94> BASF makes two (2) european formula coolants. One is sold by VW, Audi, and Mercedes Dealers. The other is sold by BMW, Saab, and Volvo dealers. The reason for the phosphate free formula is basically two-fold: (1) Cosmetics: Hard water reacts with phosphates in coolant to form scale deposits in overflow bottles. These deposits could form in other parts of the cooling system, causing blockage and overheating (see next part). (2) Corrosion: Phosphates tend to aggravate any corrosion that might already be present with any aluminum parts in the cooling system. Aluminum Phosphate is formed, which is insoluble in the ethylene glycol solution of the coolant. The aluminum phosphate will tend to settle out in the cooler areas of the cooling system, causing blockage. This can cause overheating of the engine, which will accelerate the aluminum corrosion. In other words, the corrosion will tend to feed on itself until damage is done to the engine or the coolant is replaced (refreshing the inhibitors).

Engine coolant should be REPLACED every two (2) years to refresh the silicates and other corrosion inhibitors contained in the coolant.

He was not aware of any problems with coolants containing phosphates, but did say that if the coolant was NOT replaced regularly, the inhibitors would lose their effectiveness and become weak. And that weakness could allow some aluminum corrosion to start, and become aggravated over time.

and from personal experience, the Mercedes folks are fanatic about the phosphate-free stuff being the ONLY thing to use in their engines (the service folks, that is). and i know of one toyota truck that lost a radiator and head gasket because of using a coolant that contained phosphates (in contradiction to the requirement by toyota that only the phosphate-free coolant be used). joel


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