Free Car Repair Advice by Certified ASE Technicians
How Do I Repair My Car?
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How
Do I Flush My Brake System?
How to Flush or Bleed a Car Brake System
WARNING! Always have the vehicle under inspection
on level ground, in park with the emergency brake on. Always wear protective eyewear,
gloves and necessary clothing before inspection or work begins. Never crank an engine
over when anyone is near the battery or engine. Always have an operational fire extinguisher
close by, obey all first aid instructions in the event of an injury. Never stand
in front or behind a vehicle when cranked over or running. When engine is cranked
over keep hands and clothing away from rotating components. Never move a car without
proper brake pedal operation.
Introduction
The brake fluid in your cars brake system is a hydraulic based fluid and is used
to transfer force from the brake pedal, the brake caliper or the wheel cylinder.
The purpose of the brake system fluid change is remove moisture, air and containments
from the braking system. 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. The higher boiling point the need for higher quality
brake fluid is required; 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. Always uses protective gloves, clothing and eyewear to guard against
accidental spillage. 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 if
normal brake pedal operation is not present do NOT move vehicle until further inspection
or repairs are performed.
Typical Brake Master Cylinder
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.
Getting Started
Remove brake fluid reservoir cap and insert brake fluid removal tool, 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 your owner's manual. Once the master cylinder is full loosen all four brake fluid
bleeder screws on the brake caliper or wheel cylinder. Next, press the brake pedal
down completely, while holding the brake pedal down have a helper close all four
brake bleeder screws. Now allow the brake pedal to return to normal position slowly,
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.
CAUTION: DO NOT DRIVE OR MOVE A VEHICLE UNTIL NORMAL BRAKE PEDAL OPERATION IS PRESENT!
Common Problems:
Stuck Brake Bleeder? - Is the brake bleeder screw tight? Yes
vary, this is because all bleeder screws seal against a taper fit seat in the brake
wheel cylinder or caliper to create the valve that controls brake fluid flow. When
loosening a brake bleeder always spray WD40 or equivalent to aid rust removal then
use quality tool with little to no wear on it.
No Fluid out of the Brake Bleeder? - This because the bleeder is not used very often
it can get filled with dirt and moisture, clogging the passage.
If this is the case open the bleeder 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.
How Do I Repair My Car?
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How
Do I Flush My Brake System?
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