How to bleed Master Cylinder In Car
AutoZone Car Care: How to Bleed the Master Cylinder and Brake System
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your master cylinder is the heart of
your vehicle's braking system when you
press your brake pedal it distributes
brake fluid through hydraulic lines to
four wheels of your car anytime a
hydraulic braking component is replaced
air will enter the system that can cause
a spongy pedal and reduce braking
performance to prevent this reduction in
braking the process of bleeding the
brake system must be performed in this
video we'll discuss the methods for
bleeding the brake system as well as
bleeding the master cylinder since
we'll be working under the hood it's
important to observe basic safety
precautions set the parking brake and be
sure auda matic transmissions are in
park and manual transmissions are
neutral to avoid burns allow your
vehicle to cool before doing any type of
repair don't wear loose clothing or
jewelry that could get caught in moving
parts or might bridge electrical
connections and finally always wear
proper eye protection before you begin
work be sure the vehicle is parked in a
level area and that the wheels are
chocked to prevent any unintentional
movement when bleeding the brake system
it's important that you use the correct
brake fluid always refer to your owners
manual for the type of brake fluid that
should be used in your vehicle dot three
and dot four are the most commonly used
types of brake fluid dot five and dot
5.1 are silicon based fluids which
should be used only to fill non-abs
systems that have never been previously
filled with glycol-based dot three and
dot four fluid typically dot five and
dot 5.1 fluids aren't recommended for
normal automotive use once again always
check the owner's manual to see which
fluid the manufacturer recommends for
your vehicle there are four methods for
bleeding the brake system they are
manual pressure vacuum and gravity
regardless of the type of bleeding that
is performed make sure to keep the
master cylinder full of brake fluid
during the entire process and work from
the farthest wheel from the master
cylinder first to the closest last when
bleeding a wheel that has disc brakes
attach a clear tube to the bleeder screw
on
the brake caliper for drum brakes attach
the clear tube to the bleeder screw on
the wheel cylinder and then place the
other end of the hose into a container
first we'll discuss the manual method
manual bleeding requires an assistant
inside the vehicle to apply and release
the brakes have your assistant pump the
brake pedal a few times and then hold
firm pressure with pressure being
applied to the brakes by your assistant
open the bleeder screw as brake fluid
flows through the clear tube the pedal
will begin to fall towards the floor
close the bleeder valve before the pedal
reaches the floor until your assistant
to release the pedal repeat this
procedure until a clean steady stream of
brake fluid with no air bubbles as
observed repeat this process for the
remaining bleeder screws remembering to
keep a close eye on the brake fluid
level in the master cylinder next let's
talk about vacuum bleeding vacuum
bleeding is accomplished using a vacuum
pump that you can purchase at your local
autozone attach the pump to the bleeder
screw with a clear hose open the bleeder
screw and start applying vacuum with the
pump
once you see a steady stream of clean
brake fluid close the bleeder screw and
repeat this process for the remaining
bleeder screws remembering to keep a
close eye on the brake fluid level in
the master cylinder the gravity method
is the most basic method of brake
bleeding and can be done by one person
as the master cylinder is at the highest
point in the car all bleeder screws can
be opened at the same time and gravity
will pull the fluid slowly through the
system
when brake fluid is flowing out of the
bleeder screw free of bubbles close the
bleeder screw begin this process working
with the bleeder screw farthest from the
master cylinder first and continue to
work to the bleeder screw closest
closing that one last keeping an eye on
the brake fluid level in the master
cylinder the pressure bleeding met that
requires special equipment that the
typical do-it-yourselfer doesn't have
available it's a simple process that
doesn't require an assistant but instead
uses a specialized tank commonly
referred to as a bleeder ball the
bleeder ball feeds brake fluid to the
master cylinder under pressure keeping
it full during the bleeding process
while brake fluid is pushed through the
cyst
at ten to 15 psi bleeder screws are
opened one at a time so that air can be
forced out of the system when fluid
coming out of the open bleeder screw is
clean and free of bubbles the bleeder is
closed and the process is repeated for
the remaining bleeder screws now we'll
discuss bleeding the master cylinder off
the vehicle commonly called bent
bleeding many master cylinders are
required to be bench bleeeh to avoid air
being introduced into the braking system
which can reduce braking performance
when you're bent to bleeding a master
cylinder it's best to securely fasten
the master cylinder in a vise parallel
to the floor if you're purchasing a
master cylinder you'll find that most
come with a bleeding kit but if you're
removing and reinstalling a master
cylinder you'll need to have barbed
fittings and clear tubing to complete
this job first screw the barbed fittings
into the ports on the side of the master
cylinder then insert a clear rubber tube
onto each of the fittings and place the
other end into the master cylinder
reservoir making sure the hoses are held
securely in place so that they don't
slip out if the master cylinder has a
proportioning valve attached and you are
replacing the master cylinder the
proportioning valve must be transferred
to the new master cylinder prior to
bench bleeding for proportioning valve
equipped master cylinders install the
barbed fittings and hosing to the upper
ports of the master cylinder and plug
the lower ports of the proportioning
valve once the barbed fittings and
hosing are in place and the reservoir is
full of fresh brake fluid use either a
wooden dowel a blunt metal rod or a
large Phillips screwdriver to compress
the master cylinder plunger with slow
deep strokes until there are no bubbles
coming through the clear tubing take
note that in some master cylinders it
may be necessary to apply and release
the piston up to 70 times to expel all
the air keeping the hoses and fittings
used to bleed the master cylinder in
place removed from the vise and install
on the vehicle for master cylinders
without a proportioning valve once it's
secured on the vehicle the barb fittings
and tubes can be removed and the brake
lines can be attached if the master
cylinder is equipped with a
proportioning valve have the assistant
pressed down on the pedal
and open two rear ports upper and lower
one full turn then retighten and have
the assistant released the pedal and do
the same for the front two ports this
step should be repeated at least one
more time to ensure the air is removed
between the lines and the master
cylinder after the master cylinder has
been bench bled and installed on the
vehicle fill it with brake fluid and
continue with bleeding the brakes at
each wheel to finish the process of
bleeding the brake system if you choose
to try any of these methods to bleed
your master cylinder and brake system
you can find all the parts products and
expert advice you need at your local
autozone parts are just part of what we
do get in the zone and thanks for
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