Changing the many fluids in a vehicle is always a change for the
better. Dirty engine oil, transmission fluid or anti-freeze are bad
news for a car. But what about brake fluid? Many motorists know that
this fluid should be topped off, but changed?
According to the Car Care Council brake fluid in the typical
vehicle can become contaminated in two years or less. This is
because the fluid absorbs moisture, which works its way through the
hydraulic system. Under heavy braking conditions, such as those
encountered in mountainous or hilly driving or when towing a
trailer, moisture in the overheated fluid vaporizes (boiling point
of water is lower than that of brake fluid) and braking efficiency
"Even under normal driving conditions this condition can develop
if the brake fluid is seriously contaminated" says Rich White,
spokesperson for the Car Care Council. "Not only is the fluid
vulnerable to vaporizing, it also can freeze.
Brake fluid must maintain a stable viscosity throughout its
operating temperature range. If it's too thick or too thin, braking
action is impaired. Beyond the vaporization hazard, moisture creates
an additional problem for owners of vehicles equipped with anti-lock
braking (ABS) systems. Rusted and corroded ABS components are very
expensive to replace.
How does a car owner know when to have fluid changed? The Council
recommends replacement every two years or 24,000 miles.
"Certainly it should be included with brake pad or shoe
replacement," White emphasizes. "In between, as a preventive
measure, a professional brake technician should check the condition
of the fluid with an accurate fluid test safety meter, which is
inserted into the master cylinder reservoir to record the fluid's