Front brake malfunction 106 technical training 553

Front Brake
Malfunction
106
Technical Training

553 Brake Systems
Technician Handbook
CAUTION
NOTE
Hydraulic Brake
Booster Service and
Precautions
Technical Training
107
Fluid Level Check
Before checking brake fluid level, turn the ignition OFF and pump the brake
pedal 40 times to release pressure from the accumulator and return brake fluid
to the reservoir (Note on some models the number of times the brake pedal
must be pumped may vary. Refer to the repair manual for details). Fluid level
should be at the maximum level mark on the reservoir.
Brake Booster Bleeding
Bleed the brake booster if the master cylinder is disassembled, any brake line is
disconnected from the master cylinder, or the reservoir is emptied. To bleed the
brake booster, turn the ignition ON and wait until the pump motor stops (30 to
40 seconds). Then turn the ignition OFF and pump the brake pedal 40 times.
Brake System Bleeding
Before and during brake system bleeding, check the reservoir fluid level. Turn
the ignition ON and wait until the pump motor stops (30 to 40 seconds). Bleed
air at each wheel, using the brake pedal to apply pressure as you would with a
non-ABS brake system. The accumulator provides fluid to the rear brakes
continuously. Close the bleeding screw when the fluid is free of air bubbles .
Do not allow the reservoir fluid level to go below the MIN mark during bleeding.
Air in the rear brake circuit will not cause the pedal to feel spongy.

553 Brake Systems
Technician Handbook
Connect the Techstream to DLC3, turn the ignition ON, and access the ACTIVE
TEST mode.
Loosen a rear wheel cylinder bleeder plug.
Select TRAC solenoids SRMF and SRMR (this activates the solenoids and
forces fluid to the rear wheel cylinders). To protect the solenoids, Techstream
automatically stops the active test after 2 seconds. You may need to repeat the
active test several times to remove all the air from the fluid lines.
Do not depress the brake pedal during the solenoid active test. CAUTION
Master Cylinder
Solenoid Bleeding
108
Technical Training

553 Brake Systems
Technician Handbook
Section 8 Topics
Technical Training
109
This section covers hydraulic brake force distribution, including:
1. Proportioning and bypass valves
2. Double proportioning valves
3. Load sensing proportioning valves (LSPV)
4. Load sensing proportioning and bypass valves (LSPBV)
5. Testing and adjustment

553 Brake Systems
Technician Handbook
Hydraulic Control
110
Technical Training
As dynamic conditions change during braking, a weight transfer occurs that
shifts some of the load from the rear toward the front. This effectively reduces
the braking force that can be applied through the rear wheels. Therefore a front
to rear brake force distribution is made to optimize braking performance. At
lower vehicle speeds, fluid pressure is nearly equal at both front and rear brake
assemblies as the coefficient of friction is the same front to rear; however, as
vehicle speed or brake demand increases, pressure to the rear brakes must be
reduced to prevent the wheels from locking.