Cooling System - Maintenance

REF. NO. MBNA 20/9

TO: OUR MERCEDES-BENZ PASSENGER CAR DEALERS

DATE: March 1991

SUBJECT:
ALL MODELS
ENGINE COOLING SYSTEM MAINTENANCE

A recent survey of customer vehicles showed that in many cases the engine cooling system did not contain the recommended 50/50 mixture of anticorrosion/antifreeze and water. In some instances, the coolant contained only a 5 to 10% anticorrosion/antifreeze concentration.

This bulletin serves as a reminder that it is of the utmost importance to use the recommended 50/50 mixture of M-B anticorrosion/antifreeze, part no. Q 1 03 0002, and water to provide the best possible protection against boil-over and freezing, as well as corrosion protection of the cooling system, especially the radiator.

The coolant solution should always be checked following a repair on the cooling/heating system, especially after topping up to the appropriate coolant level. Refer to chapter "Coolants" in the Owner's Manual for further information.

A solution with too high anticorrosion/antifreeze concentration will hinder the heat dissipation, causing the engine temperature to increase, while a low percentage solution can cause a chemical reaction. Both factors cause damage to plastic parts of the cooling system, with subsequential damage to the radiator and engine.

The coolant should be renewed every 3 years, as stated in the Maintenance Sheet, to retain a high level of protection, since beyond that time span the additives in the anticorrosion/antifreeze will start to wear off.