Step by step guide on how to bleed and flush and brake system. This articles
pertains to most vehicles.
Difficulty Scale: 2 of 10
Tools and Supplies Needed
Small wrench set
Protective clothing and gloves
Start with the car on level ground, engine OFF, lifted safely using jack stands.
Step 1 - Identify brake master cylinder components,
brake fluid cap, brake master cylinder, fluid lines, and brake fluid level sensor.
Inspect for any brake fluid leakage around the master cylinder and check for proper
fluid level regularly. If leakage is present replace master cylinder immediately.
Master cylinder replacementStep 2 - Remove brake fluid reservoir cap and insert
a brake fluid removal tool (turkey baster), remove as much brake fluid as possible,
then refill the master cylinder with new fluid. Most cars use DOT3 or DOT4, but
you should consult the cap on the master cylinder or a service manual.
Step 3 - Once the master cylinder is full loosen
all four brake fluid bleeder screws on the brake calipers or wheel cylinders. Next,
have a helper slowly press the brake pedal down completely, while holding the brake
pedal down, close all four brake bleeder screws. Allow the brake pedal to slowly
return to normal position, this will draw new fluid into the master cylinder body.
Continue this procedure until the brake fluid is clean out of each bleeder, close
all bleeders and refill the master cylinder to the proper level. (Note: Always keep
proper fluid level in the master cylinder during this operation.)
The brake fluid in your cars brake system is a hydraulic based fluid that is
used to transfer force from the brake pedal to the brake caliper or wheel cylinder.
The purpose of the brake system fluid change is remove moisture which contaminates
the fluid and causes brake system failures. This service also replaces fluid that
has been broken down by today’s complex ABS systems. Moisture is the leading cause
of brake system operation failure. Brake fluid is subject to extreme pressure and
heat so the boiling point of brake fluid is important. Higher boiling points (severe
duty) and Anti-Lock braking systems require higher quality brake fluid; this fluid
must also have a very low freezing point. There are several forms of brake fluid
that are rated by the government for the various boiling points and other factors.
These rating are DOT2, DOT3, DOT4 and DOT5. Distinctive ratings define the chemicals
the fluid is produced with such as, mineral oil, ester glycol esters and synthetic
oils. Many of these fluids are not compatible so make sure you add and flush your
brake system with the manufacturers recommended brake fluid. Almost all brake fluid
is corrosive and extreme care must be used when handling brake fluid.
If any brake fluid is spilled, flush thoroughly with water, this goes for human
contact as well as spillage on your vehicles paint. Always add brake fluid from
a sealed container and never allow moisture into the brake fluid. A brake system
flush is used to remove any moisture and dirt out of the system and replace it with
new fluid. After a flush is complete a full system bleed procedure is required,
always check brake pedal operation after the work is complete, if normal brake pedal
operation is not present DO NOT move vehicle until further inspection or repairs
are performed and normal braking operation has resumed.
Common ProblemsStuck Bleeder Valve - The brake bleeder screw can be very tight, this
is because all bleeder screws seal against a taper fit seat in the wheel cylinder,
or caliper. When loosening a brake bleeder always spray WD40 or equivalent to aid
rust removal then use a quality tool with little to no wear on it, 6 point wrench
or socket is best.
No Fluid Flowing Out of the Brake Bleeder - This can be because the bleeder
is not used very often so it can get filled with dirt and moisture clogging the
passage. If this is the case open the plugged bleeder (with other 3 closed) and
press the brake pedal down, this additional pressure from the other bleeders being
closed will force the fluid out of the plugged bleeder. Once the bleeder has become
unplugged finish the bleeding procedure until clean fluid is present. Then close
the bleeder and release the brake pedal slowly.
Always uses protective gloves, clothing and eyewear to guard against accidental
Written by Ken Lavacot Co-Founder and CEO of 2CarPros.com 35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.
COMMENTS TO THIS ARTICLE
Please use our question form if you have a specific question about your car as we are not able to give you a full answer on this page.
Article first published 2009-08-26 (Updated 2015-01-05)