Risk of accidents from brake fluid contaminated with water
Water contaminated oil lowers its boiling point. Air bubbles form, rendering the brake system ineffective when they overheat.
About half of all cars and trucks over 10 years old in the United States have never had their brake fluid changed. Many European countries require regular brake fluid testing, and nearly half have found defects.
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Brake fluid plays an important role in maintaining safety while driving. Technology experts recommend that car owners should change the brake fluid if it is contaminated with water or dirt or change it periodically every 1-2 years.
The reason given by experts is that brake fluid contains glycol. This is a strong water absorbent. Over time, water vapor can penetrate rubber hoses and gaskets. This phenomenon appears clearly if the vehicle is used in an environment with high humidity.
Brake fluid can contain up to 2% water after 1 year of use, 3% after 18 months. It is not difficult to find samples of oil containing 7-8% water if the car is used for several years.
According to an investigation by the US National Highway Traffic Safety Administration, up to 20% of 1,720 vehicles had brake fluid containing more than 5% water. Water-contaminated oil has a lower boiling point than “dry” oil. DOT 3 oil boils at 205 degrees Celsius, but when wet, it only boils at 140 degrees Celsius. The boiling point of most new DOT fluids is around 240 to 260 degrees Celsius.
Mixed with 1% water, DOT 3 boils at 187 degrees C. Mixed with 2% water is 160 degrees C. If 3% oil boils at 145 degrees C.
DOT 4 oil absorbs moisture more slowly, but its boiling point drops more than DOT 3. If 3% water is present, the boiling point of DOT 4 can be reduced by half.
Overheating of the brake system causes the oil to boil, creating air bubbles. Displacing the liquid oil in the system, air bubbles render the brake system ineffective even if the driver applies the brakes hard. In addition, water-contaminated oil accelerates the corrosion of brake system components, ABS.
Brake systems with mixed fluid easily pass the safety tests. The fluid level is within acceptable limits, the lines are good, and the brakes feel effective. But all that changes when the system gets hot and bubbles form.
