Hydraulic Brake System Bleeding When to Bleed Brake System
A bleeding operation is necessary to remove any air that
is introduced into the hydraulic brake system.
It may be necessary to bleed the hydraulic system at all four brake
bleeder screws if air has been introduced through low fluid level or by disconnecting
brake pipes at the master cylinder. If a brake hose is disconnected at
one wheel, only that wheel caliper needs to be bled. If brake pipes or
hoses are disconnected at any fitting located between master cylinder
and brakes, then the brake system served by the disconnected pipe or hose
must be bled.
Hydraulic Brake System Bleeding Manual
The time required to bleed the hydraulic system can be
reduced if the master cylinder reservoir is filled with brake fluid and as
much air as possible is expelled before the master cylinder is installed
on the vehicle. Pumping the piston can evacuate the air from the piston
cavities.
Power brakes require the vacuum reserve be depleted by applying the
brakes several items with the engine off. Care must be taken to prevent brake
fluid from contacting any painted surface. Use rags to catch the excess
fluid.
- Fill the master cylinder
reservoir with brake fluid and keep the reservoir at least half full of fluid
during the bleeding operation.
Notice: Use the correct fastener in the correct location. Replacement fasteners
must be the correct part number for that application. Fasteners requiring
replacement or fasteners requiring the use of thread locking compound or sealant
are identified in the service procedure. Do not use paints, lubricants, or
corrosion inhibitors on fasteners or fastener joint surfaces unless specified.
These coatings affect fastener torque and joint clamping force and may damage
the fastener. Use the correct tightening sequence and specifications when
installing fasteners in order to avoid damage to parts and systems.
- If the master cylinder
is known or suspected to have air in the bore, then it must be bled in the
following manner, before bleeding any caliper:
| 2.1. | Disconnect the forward (blind end) brake pipe connection at the
master cylinder. |
| 2.2. | Allow the brake fluid to fill the master cylinder piston bore
until it begins to flow from the forward pipe connector port. |
| 2.3. | Connect the forward brake pipe to the master cylinder and tighten. |
| 2.4. | Depress the brake pedal slowly one time and hold. Loosen the forward
brake pipe connection at the master cylinder to purge air from the bore.
Tighten the connection and then release the brake pedal slowly. Wait
15 seconds. Repeat the sequence, including the 15 second wait, until
all air is removed from the bore. |
Tighten
Tighten the brake pipe tube nut to 18 N·m (13 lb ft).
| 2.5. | When clear fluid flows from the forward connection, repeat steps
1 and 2 to bleed the master cylinder at the rear (cowl) connection. |
- Individual brake calipers
are bled only after all air is removed from the master cylinder. If it is
known that the brake calipers do not contain any air, then it will
not be necessary to bleed them.
| 3.1. | Place a proper size box end wrench, or equivalent, over the brake
caliper bleed screw. Attach a clear tube over the screw. Submerge the other
end of the tube in a clear container partially filled with brake fluid. |
| 3.2. | Depress the brake pedal slowly one time and hold. Loosen the brake
caliper bleed screw to purge the air from the cylinder. Tighten the brake
caliper bleed screw and slowly release the pedal. Wait 15 seconds.
Repeat the sequence, including the 15 second wait, until all
air is removed. It may be necessary to repeat the sequence 10 or more
times to remove all the air. Rapid pumping of the brake pedal pushes
the master cylinder secondary piston down the bore in a way that makes
it difficult to bleed the system. |
Tighten
Tighten the brake caliper bleed screws to 12 N·m (106 lb in).
| 3.3. | If it is necessary to bleed all of the brake calipers, the following
sequence should be used: |
| 3.4. | Check the brake pedal for sponginess. |
Hydraulic Brake System Bleeding Pressure
Tools Required
J 35589 Pressure Bleeding
Adapter
- Remove the master cylinder
reservoir cap. Replace it with J 35589
.
- Charge the bleeder to 140-172 kPa (20-25 psi).
- Connect the hose to J 35589
.
- Raise the vehicle and support. Refer to
Lifting and Jacking the Vehicle
in General Information.
- If it is necessary to
bleed all of the brake calipers, the following sequence should be used:
- Place the proper size box end wrench, or equivalent, over the
brake caliper bleed screw. Attach a clear tube over the screw and allow the
tube to hang submerged in a clear container partially filled with brake
fluid.
- Open the brake caliper bleed screw at least ¾ of a turn
and allow the brake fluid flow to continue until no air is seen in the brake
fluid. Apply intermittent pressure to the brake pedal while pressure
bleeding.
Notice: Use the correct fastener in the correct location. Replacement fasteners
must be the correct part number for that application. Fasteners requiring
replacement or fasteners requiring the use of thread locking compound or sealant
are identified in the service procedure. Do not use paints, lubricants, or
corrosion inhibitors on fasteners or fastener joint surfaces unless specified.
These coatings affect fastener torque and joint clamping force and may damage
the fastener. Use the correct tightening sequence and specifications when
installing fasteners in order to avoid damage to parts and systems.
- Close the brake caliper
bleed screw.
Tighten
Tighten the brake caliper bleed screw to 12 N·m (106 lb in).
- Repeat steps 6 through 8 until all of the calipers have been bled.
- Lower the vehicle.
- Check the brake pedal for sponginess. Auto bleed the modulator
and repeat the entire bleeding procedure to correct this condition. Refer
to
Antilock Brake System Automated Bleed Procedure
in
ABS.
- Remove the brake bleeding equipment from the master cylinder.
