Brake Fluid Flush? What is it And Does My Car Need It?

Do I need to flush my
brake fluid?

Reader Question:
I brought my 2000 Chevy S10 for a routine oil change. I got talked into
having my brake fluid flushed at a cost of $89.00. The mechanic said it
was dirty and needed flushing because of the ABS anti-locking brakes. I
told him I never heard of that before. My truck only has 23k miles on
it. Was I ripped off?
Thank you,
Joseph

Dear Joseph,

I know you must have been a little
surprised to hear your truck needed to have the brake fluid replaced.
But actually, this mechanic was probably doing you a good deed. Brake
fluid attracts moisture, and this moisture can rust the insides of the
brake system. This moisture was not that big of deal 10 years ago, but
on ABS brake systems of today, the rust and other debris that
accumulates in the fluid can do lots of internal damage, and can be very
costly. Brake fluid can also break down over time from excess heat that
is created from within the brake system.

At my shop we recommend flushing the
brake fluid system about every 30,000 miles, or whenever we are
performing a brake job. To do this flush, we open the brake lines
located at each wheel and allow the brake fluid from the brake master
cylinder to "gravity bleed" as we continue to feed new fluid
to the master cylinder until the fluid runs clear at all wheels. By
gravity bleed I mean without the assistance of anything other than
allowing the fluid to slowly drip from the lines by the natural force of
gravity.

You are probably familiar with the term
"bleeding the brakes" when talking about a brake job. When the
brake lines are opened or any work is performed to the brake system that
can allow air to get trapped within the lines, the brakes must be bled
of air. In the earlier days, the mechanic would bleed the brakes by
having someone pump and hold pressure on the brake pedal as he opened
the brake lines located at each wheel. This method of bleeding the
brakes is not a recommended procedure for newer brake systems (discussed
later).

What is the difference between
flushing and bleeding? Flushing is just that, flushing the old
dirty fluid out of the system and replacing it with new clean fluid.
Bleeding usually consists of removing just enough brake fluid to get out
the air pockets that have become trapped in the system, and usually does
not focus on the time consuming process of removing the dirt and old
fluid from the system.

One side note learned by experience. If
you are interested in doing a brake fluid flush on your own vehicle, be
warned of the potential dangers. Foremost, follow the brake bleeding
procedures outlined in the repair manual you should be using. Stepping
on the brake pedal with the brake lines cracked open can cause the dirt
and debris to be pushed into the body of the master cylinder, thus
causing damage to internal parts and seals of the master cylinder and
the anti-lock brake components. Stepping on the brake pedal as someone
under the vehicle opens each brake line at the wheel used to be the way
you bled brakes, but not anymore.

Gravity bleeding does take a little
longer to perform and can require a lot of new brake fluid to push out
the old dirty fluid, but the risk of doing internal damage to the
anti-lock system is greatly reduced. They also make vacuum assisted
brake bleeding and flushing equipment to help speed up the process.

How can you tell if your vehicle
is due for a brake fluid flush? They make special test strips
which can detect high levels of moisture present in the brake fluid, but
I prefer the old fashioned eye ball method personally. Remove the brake
master cylinder cap and visually inspect the condition of the fluid. Brake
fluid should be clear or a slight yellowish tent, so black or dark
colored dirty fluid should be quite obvious even to the untrained eye.