Cooling System - Approved Phosphate Free Anti-Freeze

Group
1

Model
4 Cyl. & 8 Cyl.

Part Identifier
1901

Number
9408

August 30, 1994

Subject:
Approved Anti-Freeze

ATTENTION: Service Manager/Service Technician

Models Affected:
924, 944, 968 and 928

Concern:
Use of approved phosphate free anti-freeze in Porsche all aluminum engines.

All full-aluminum water cooled Porsche engines should only use approved, phosphate free anti-freeze. This anti-freeze may be obtained from Audi/Volkswagen or Mercedes Benz dealers under the brand names "Autobahn" and "Mercedes Benz" respectively. Where available, "Zerex Extreme 450" may also be used.

General Information:

The anti-freeze is not only for freeze/boiling protection, but also protects the cooling system from corrosions. To have a correct corrosion protection level in the coolant system, anti-freeze must remain in the coolant system year round. Therefore, the concentration of anti-freeze to water should not be less than 30% by volume.

Mixing:

Different makes of anti-freezes usually mix; however, in some there are great differences in quality. Therefore, the concentration of anti-freeze to water should not be less than 30% by volume.

Mixing Table

Freeze protection to: Anti-Freeze Water

-30°C (-22°F) 45% 55%
-35°C (-31°F) 50% 50%
-40°C (-40°F) 55% 45%

A higher than 55% by volume anti-freeze concentration shoold be avoided, since the heat dissipation ability of the coolant will be reduced.

Coolant Volume:

Type 924 - approx. 7.0 liter
Type 944/968 - approx. 7.8 liter
Type 928 - approx. 16.0 liter

Topping-up of Coolant:

The effectiveness of the anti-freeze in the coolant becomes less after a longer time period of operation. If, due to coolant loss, coolant/anti-freeze must be added, an approved quality anti-freeze should be used. In this case it need not be the same approved brand.

Coolant Change:

Every two (2) years, the coolant/anti-freeze should be changed to assure the effectiveness of the coolant.

If the engine coolant has to be drained on cars in service over one (1) year, it is recommended to use new coolant/anti-freeze.

Important Note:
Anti-freeze with ethylene glycol or propylene glycol base is available; however, anti-freeze with a propylene glycol base is not approved for Porsche vehicles.

The corrosion protection and anti-freeze characteristics of propylene glycol are different, although their physical characteristics are similar. A simple test is not possible to differentiate between the two.

If propylene glycol is used or added to a Porsche vehicle or if it is not known what type of anti-freeze has been used, the anti-freeze should be changed completely to an approved brand.