Cooling System - New Antifreeze
Group 17Radiator
Bulletin Number
17 01 88 (1743)
Woodcliff Lake, NJ
July 1991
Service Engineering
This Service Information Bulletin supersedes S.I. 17 01 88 (1743) dated November 1988. It lists a revised part number for antifreeze and makes reference to recycled antifreeze in this bulletin. Please remove and discard S.I. 17 01 88 (1743) dated November 1988 from your S.I. binder.
SUBJECT:
New BMW Antifreeze
MODELS:
All
Situation:
A properly functioning cooling system is vital for the engine's durability. Coolants must fulfill four basic requirements:
^ Guarantee sufficient cooling.
^ Guarantee operation of cooling system in winter (prevent freezing of coolant) and in summer by boosting the boiling point.
^ Protect various metals (gray cast iron, steel, aluminum, brass, copper and solder) against corrosion.
^ Prevent excessive silicate gel precipitation, which may cause plugging of the cooling system.
Lately, silicate gel precipitation has become a major concern of the automotive industry and its customers as well.
In the attempt to protect aluminum engine parts effectively against corrosion, the amount of silicates was increased by antifreeze manufacturers.
Excessive silicate gel dropout (also known as the "Green Goo", even if the color might differ) depends mainly on the silicate content itself - also as a consequence of an antifreeze over-concentration in the coolant, the water hardness and phosphates as part of certain, commonly used antifreeze additives.
As a result of chemical reactions among the above mentioned components, this gel builds up inside the complete cooling system and especially inside the radiator. It acts like a heat insulating coating, thus reducing the heat transfer from engine components to the coolant and/or from the coolant to the air flowing through the radiator.
Consequently, the coolant temperature level inside the entire coolant circuit increases with increasing gel development until the point can be reached where the engine might partially or totally overheat with the result of considerable damage.
Solution:
BMW of North America is proud to introduce a new antifreeze, which was developed especially to prevent excessive silicate drop-out without taking any shortcuts concerning the well-known and general requirements for a coolant antifreeze. This BMW tested and approved antifreeze, containing no nitrites and no phosphates, can be ordered in a 1 gallon container under P/N 88 88 6 900 316.
The initial fill of the coolant system is 50% antifreeze and 50% water. Maintain this mixture when changing the coolant, as it provides the best overall performance. Freezing protection with this mixture is provided down to -34~F (-37~C). During winter in extremely cold areas, the antifreeze can be increased up to 60%, which provides freezing protection down to -62~F (-52~C). Do not exceed a 60% ratio of antifreeze.
NOTE:
^ Do not mix any additives or other components into the coolant.
^ To maintain protection against excessive silicate precipitation, do not mix with different antifreeze containing nitrites and/or phosphates and a high silicate formulation.
Although it is the policy of BMW to support most forms of recycling, it is not recommended to use recycled antifreeze in BMW automobiles.
Used coolant/antifreeze has an altered chemical stability (silicate balance) which reduces the efficiency of today's coolant systems. Only the use of new coolant/antifreeze at the recommended change intervals will assure reliable engine coolant system operation under all conditions.
For more information on the proper disposal of used antifreeze, refer to S.I. 04 12 91 (3286).