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2-2
PART
2-1
GROUP
2~BRAKES
GENERAL BRAKE SERVICE
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1 Diagnoiis and Testing
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2-2
Secdoll
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Preliminaey Tests
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2-2
3. Cleaning and Inspection
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2-4
Road Test
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2-3
Disc Brake Trouble Symptoms and Po11ible
2-6
Causes
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2 Common Adjustments and Repairs
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2-3
Drum Brake Trouble Symptoms and Possible
2-7
Parking Brake Linkage Adjustment
2- 3
Hydraulic System Bleeding
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2-3
Causes
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II
DIAGNOSIS AND TESTING
PRELIMINARY TESTS
FLUID LEVEL
Always check the fluid level in the
brake master cylinder reservoirs be-
fore performing the test procedures.
If necessary, top up the master
cylinder reservoirs to the level indi-
cated on the side of the reservoir,
using only the specified brake fluid,
Motorcraft Brake Fluid.
AUTOMATIC ADJUSTERS
Push the brake pedal down as far
as it will go while the car is standing.
If the car is equipped with power
brakes, the engine should be running
while making this test. If the brake
pedal travels more than half-way
between the released position and
the floor, check the automatic adjus-
ters for being inoperative. To check
adjuster operation, make several
sharp reverse stops (equivalent to 50
pounds pedal pressure) with a for-
ward stop before each. Move the
vehicle forward for a distance of
approximately ten feet; then reverse
for ten feet, apply the brakes sharply
and hold the brake pedal down until
the vehicle is completely stopped. This
will actuate the brake self-adjusters.
If these stops do not bring the brake
pedal travel within specification,
make several additional forward and
reverse stops as outlined above.
If
the second series of stops do
not bring the brake pedal travel
within specifications, remove the
brake drums and check the brake
adjusters to make sure $ey are
functioning. Check the brake linings
for wear or damage. R,epair or replace
all worn or damaged parts and non-
functioning adjusters. Adjust the
brake lining outside diameter to the
approximate inside diameter of the
brake drum.
If all the brake adjusters, brake
drums and linings are functional and
the brake travel is not within specifi-
cations, check the pedal linkage for
missing or worn bushings, or loose
attachments. Bleed the brakes.
HYDRAULIC
SYSTEM
If the car is equipped with power
brakes, shut off the engine and ex-
·
haust all vacuum from the booster
system before performing this tesL
Depress the brake pedal and hold
it in the applied position. If the pedal
gradually falls away under this pres-
sure, the hydraulic system is
leaking.
Check all tubing, hoses, and con-
nections for leaks.
If the brake pedal movement feels
spongy, bleed the hydraulic system
to remove air from the lines and
cylinder.
See Hydraulic
System
Bleeding, Page 2-3. Also, check for
leaks or insufficient fluid.
-
POWER BRAKE
FUNCTIONAL
TEST
With the transmission in neutral,
stop the engine and apply the park-
ing brake. Depress the service brake
pedal several times to exhaust all
vacuum in the system. Then, depress
the pedal and hold it in the applied
position. Start the engine. If the
vacuum system is operating the pedal
will tend to fall away under foot
pressure and less pressure will be
required to hold the pedal in the
applied position. If no action is felt,
the vacuum booster system is not
functioning.
Refer to Table
.1,
Page 2-6.
For booster removal and instal-
lation procedures refer to Page 2-20.
For cleaning and inspection refer
-
to Page
_
2-4.
LOCKED BRAKES
Should one of the brakes be locked
and the car must be moved, open the
brake cylinder bleeder screw long
enough to let out a few drops of
brake fluid. This
bleeding opera-
don will release the brakes, but
it will not correct the cause or
the
trouble.
BRAKE
WARNING
LIGHT
The three tests listed below are
applicable to all models with either
drum or disc brakes.
1. Tum the ignition switch to
the ON position. If the light on the
brake warning lamp illuminates, the
condition may be caused by:
(a) a defective switch.
(b) grounded switch
wires.
(c) the differential valve switch not
having been reset after having
been activated.
·
The differential valve switch is
spring loaded. and does not have to be
reset, however it must be removed
from the .master cylinder to allow the
differential valve to centralise. The
valve is self-centering only when the
switch is removed. When either sys-
tem is being bled the switch must be
removed to prevent damage to the
plunger. Except on G.T. vehicles
when the valve must be centralised
by relieving pressure in the approp-
riate system after bleeding.
2. Tum the ignition switch to the
START position.
If the brake
warning lamp does not light, check
the bulb and wiring for defects and
repair or replace as necessary.
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