2003 FORD MUSTANG brakes

in the brake master cylinder reservoir are also indicators of system concerns.
If a wheel is locked and the vehicle must be moved, open a bleeder screw at the locked wheel (1007)
to let out enough fluid to relieve the pressure. Close the bleeder screw. This bleeding operation may
release the brakes but will not correct the cause of trouble. If this does not relieve the locked wheel
condition, repair the locked components before proceeding.
Inspect all hoses and connections. All unused vacuum connectors should be capped. Make sure
hoses and their connections are correctly secured and in good condition with no holes, soft or
collapsed areas.
Non-
Pressure Leaks
The only part of the brake system that could have a brake fluid loss that does not appear when the
system is under pressure is the brake master cylinder reservoir area. Brake fluid loss can be caused
by a missing or poorly- fitted brake master cylinder filler cap (2162), a punctured or otherwise damaged
brake master cylinder reservoir, a missing or damaged brake master cylinder filler cap gasket, or by
missing, damaged or poorly- fitted sealing grommets between the brake master cylinder (2140) and the
brake master cylinder reservoir.
The brake master cylinder reservoir grommets are not separately serviceable and must be installed
new as part of a new brake master cylinder reservoir.
Install a new flexible brake hose if it shows signs of softening, cracking or other damage.
When installing a new brake hose, position the hose to avoid contact with other vehicle components.
Road Test
Perform a road test to compare actual vehicle braking performance with the performance standards
expected by the driver. The ability of the test driver to make valid comparisons and detect performance
deficiencies will depend on experience.
The driver should have a thorough knowledge of brake system operation and accepted general
performance guidelines in order to make good comparisons and detect performance problems.
Select a road that is reasonably smooth and level. Gravel or bumpy roads are not suitable because the
surface does not allow the tires to grip the road equally. Avoid crowned roads.
A key factor in evaluating brake concerns is the deceleration rate. This varies from vehicle to vehicle
and with changes in operating conditions. It is evident how well the brakes are working after just a few
applications.
Avoid locking the brakes. Locked brakes are not an indication of braking efficiency.
Visual Inspection Chart Mechanical Electrical
z
Brake master cylinder
z Brake caliper piston
z Brake discs
z Brake pads z
Parking brake switch
z Damaged or corroded wiring harness
z Brake master cylinder fluid level switch Klj . 2 ba
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For low or spongy brake pedal concerns:
zcheck and, if necessary, refill the brake master cylinder reservoir.
z bleed the brake system and retest the brake pedal feel.
z if the brake pedal is still low or feels spongy, check the brake pedal mounting for looseness and
correct installation. Check the power brake booster and the brake master cylinder for loose
mounting. Correct as necessary and retest the system for normal operation.
For a slow or incomplete brake pedal return concern:
zinspect for binding, damage, correct installation or interference at the brake pedal.
z check the power brake booster for binding, damage and correct installation.
Vibration When Brakes are Applied
For vibration concerns when brakes are applied, perform the following procedure.
Visually inspect: ztire condition and pressure.
z suspension bushings and ball joints.
Correct as necessary. 1. Verify and isolate the concern. Brake roughness can be felt in: zthe steering wheel.
z the seat.
z the brake pedal.
2. After verifying the concern, check for related concerns in the: zOn- Line Automotive Service Information System (OASIS).
z Technical Service Bulletins.
3. Check wheel bearing end- play and correct as necessary.
4. NOTE: Begin at the front of the vehicle unless the vibration has been isolated to the rear.
Remove the tire and wheel.
5. Remove the brake caliper.
6. Measure and record the brake disc thickness. Install a new brake disc if the thickness after machining will be at or below specification. The specification is molded into the brake disc. Do z
Power brake booster
z Brake pedal linkage
z Vacuum booster hose
z Tires
z Foreign material Klj . 3 ba
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not machine a new brake disc.
7. For vehicles with a two- piece hub and brake disc assembly:
z Match-mark before disassembly.
z Remove the brake disc.
z Using a die grinder with a mild abrasive (Scotch Brite® type), remove any rust or
corrosion from the hub and brake disc mounting surfaces.
z Align the match- marks and reinstall the brake disc on the hub.
8. CAUTION: Do not use a bench lathe to machine brake discs.
NOTE: The depth of cut must be between 0.10 and 0.20 mm (0.004 and 0.008 inch). Lighter
cuts will cause heat and wear. Heavier cuts will cause poor brake disc surface finish.
Using on- vehicle brake lathe, machine the brake discs. Follow the manufacturer's instructions.
After machining, make sure the brake disc still meets the thickness specification.
9. Using a dial indicator, verify that the brake disc lateral runout is now within vehicle specification.
10. Remove any metal chips.
11. Remove the hub adapter.
12. Remove any remaining metal chips from the machining operation.
13. CAUTION: Do not carry out this step on rear drum- in-hat brake discs.
For vehicles with a two- piece hub and a non drum- in-hat brake disc assembly:
z Remove the brake disc from the hub.
z Remove any remaining metal chips from hub and brake disc mounting surfaces and from
the ABS sensor.
z Apply High Temperature Nickel Anti- Seize Lubricant F6AZ-9L494-AA to the mounting
surfaces.
z Using the match- marks, mount the brake disc on the hub.
14. Install the caliper and check brake operation.
Symptom Chart Symptom Chart
Condition
Possible Sources Action
z The Brakes Pull or
Drift z
Tire air pressure.
z Wheel alignment.
z Brake pads.
z Brake components.
z Suspension
component. z
Go To Pinpoint Test A .
z The Red Brake
Warning Indicator Is z
Instrument cluster.
z Circuit. z
Go To Pinpoint Test B . Klj . 4 ba
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Always On
zParking brake.
z Brake fluid level.
z Vibration When
Brakes Are Applied z
Rear disc brakes.
z Front disc brakes. z
REFER to Section 100 -
04 .
z Brake Pedal Goes
Down Fast z
Brake fluid level. zFILL the brake master
cylinder reservoir.
BLEED the system.
z Air in system. zBLEED the system.
z Brake master
cylinder. z
PERFORM the brake
master cylinder
component test in this
section.
z The Brake Pedal
Eases Down Slowly z
Air in system. zBLEED the system.
REFER to Bleeding —
System in this section.
z Brake master
cylinder. z
PERFORM the brake
master cylinder
component test in this
section.
z Brake Lockup During
Light Brake Pedal
Force z
Disc brake
component.
z Parking brake
component.
z Anti- lock brake
control system. z
Go To Pinpoint Test C .
z Excessive/Erratic
Brake Pedal Travel z
Leak in hydraulic
system.
z Air in system.
z Disc brake caliper.
z Brake master
cylinder. z
Go To Pinpoint Test D .
z Brakes Drag zParking brake
component. z
REPAIR or INSTALL new
components as
necessary. REFER to
Section 206 - 05 .
z Disc brake caliper. zREPAIR or INSTALL a
new brake caliper as
necessary. REFER to
Section 206 - 03 and
Section 206 - 04 .
z Brake booster-to-
brake master
cylinder push rod
adjustment. z
ADJUST the push rod.
REFER to Section 206 -
07 .
z Brake master
cylinder. z
PERFORM the brake
master cylinder
component test in this
section.
z Excessive Brake
Pedal Effort z
Power brake
booster. z
PERFORM the brake
booster component test
in this section.
z Power brake
booster check
valve (2365). z
PERFORM the check
valve component test in
this section.
z Power brake
booster hose. z
REROUTE, REPAIR or
INSTALL a new brake Klj . 5 ba
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Pinpoint Tests
PINPOINT TEST A: THE BRAKES PULL OR DRIFT booster hose as
necessary.
z Red Brake Warning
Indicator Inoperative z
Circuit.
z Bulb. z
REFER to Section 413 -
01 .
z Brake Noise zDisc brake
component. z
MACHINE or INSTALL a
new brake component as
necessary. REFER to
Section 206 - 03 or
Section 206 - 04 .
z Hydro-Boost, No
Power Assist z
Power steering
pump.
z Linkage.
z Power steering
fluid flow.
z Hydro-boost unit. z
Go To Pinpoint Test E .
z Hydro-Boost Erratic
Operation, Sticks,
Binds or Grabs z
Supply hose.
z Hydro-boost unit. z
Go To Pinpoint Test F .
z Hydro-Boost Brake
System Operation
Suspect z
Leakage.
z Hydro-boost unit. z
Go To Pinpoint Test G .
Test Step Result / Action to Take
A1 CHECK THE TIRES
NOTE:
Check tire pressure with the brakes off.
z Check tires for uneven and excessive wear and for correct
pressure.
z Are the tires OK? Yes
GO to
A2 .
No
CORRECT as necessary.
RETEST for normal
operation. A2 CHECK THE ALIGNMENT
z
Check the caster, camber and toe. Refer to Section 204 -
00 . Yes
GO to
A3 .
No
CORRECT alignment as
necessary. REFER to Section 204 - 00 . RETEST for correct
operation. Klj . 6 ba
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PINPOINT TEST B: THE RED BRAKE WARNING INDICATOR IS
ALWAYS ON z
Is the alignment OK? A3 CHECK THE DISC BRAKE COMPONENTS
z
Check all disc brake calipers, anchor plate guide pins and
brake pads for binding, wear, damage, contamination and
correct installation.
z Are the disc brake calipers, anchor plate guide pins
and brake pads OK? Yes
GO to
A4 .
No
REPAIR or INSTALL new
components as necessary.
RETEST for normal
operation. A4 ROAD TEST THE VEHICLE
z
Road test the vehicle, and observe whether the drift
occurs with or without the brakes applied.
z Does the drift or pull occur with the brakes applied? Yes
REPAIR or INSTALL new
front disc brake caliper or
anchor plate guide pins on
the side opposite to the
direction of the drift or pull.
No
REPAIR or INSTALL new
front disc brake caliper or
anchor plate guide pins on
the side of the vehicle in the
direction of the drift or pull.
Test Step Result / Action to Take
B1 CHECK THE BRAKE MASTER CYLINDER FLUID
LEVEL SWITCH z
Key in OFF position.
z Disconnect: Brake Master Cylinder Fluid Level Switch
C124.
z Connect a fused jumper from C124- 2 circuit 977
(PK/WH) to C124- 3 circuit 128 (VT/YE). Yes
GO to
B2 .
No
INSTALL a new brake master Klj . 7 ba
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The function of the power brake booster check valve is to allow manifold vacuum to enter the power
brake booster and prevent the escape of vacuum in case manifold vacuum is lost during sustained full
throttle operation.
To test the function of the power brake booster check valve :
zStart and run the engine for at least 10 seconds.
z Operate the brake pedal to check for power assist.
z Disconnect the vacuum booster hose from the power brake booster check valve. Do not remove
the power brake booster check valve from the power brake booster.
z There should be enough vacuum retained in the brake booster for at least one more power-
assisted brake operation.
Brake Master Cylinder — Normal Conditions
The following conditions are considered normal and are not indications that the brake master cylinder
is in need of service.
Condition 1: During normal operation of the brake master cylinder, the fluid level in the brake master
cylinder reservoir will rise during brake application and fall during release. The net fluid level (i.e., after
brake application and release) will remain unchanged.
Condition 2: A trace of brake fluid will exist on the booster shell below the master cylinder mounting
flange. This results from the normal lubricating action of the master cylinder bore and seal.
Condition 3: Fluid level will decrease with pad wear.
Brake Master Cylinder — Abnormal Conditions
Changes in brake pedal feel or travel are indicators that something could be wrong in the brake
system. GO to Symptom Chart for abnormal condition diagnosis.
Bypass Condition Test 1. Disconnect the brake lines at the brake master cylinder.
2. Plug the outlet ports of the brake master cylinder.
3. Apply the brakes. If brake pedal height cannot be maintained, the brake master cylinder has an internal leak and must be rebuilt or replaced.
Compensator Port Check
The purpose of the compensator ports in the brake master cylinder is to supply any additional brake
fluid required by the system due to brake pad wear and to allow brake fluid returning from the brake
lines to the brake master cylinder to enter the brake master cylinder reservoir.
The returning brake fluid will cause a slight turbulence in the brake master cylinder reservoir. Klj . 14 ba
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GENERAL PROCEDURES
Hydraulic Leak Check
1. NOTE: Brake fluid is water soluble and it is possible that all evidence of fluid leakage has been
washed off if the vehicle has been operated in the rain or snow.
Make sure the brake master cylinder reservoir (2K478) is full.
2. Apply the brakes several times and make sure the brake pedal (2455) feel is not spongy. If necessary, bleed the system. For additional information, refer to Bleeding — System in this
section.
3. If the reservoir level is dropping, inspect the brake components, fittings and lines to locate the source of the leak.
SECTION 206-
00: Brake System — General Information 2003 Mustang Workshop Manual Klj . 1 ba
12003 Mustang Workshop Manual
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