Ford Fusion Quiz
Chassis

Brake System. Diagnosis and Testing

In this manual: Chassis
General Information — 26Chassis — 150Powertrain — 282Electrical — 271Body and Paint — 300
18steps
~108min
4/5difficulty
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Symptom Chart

Symptom Chart: Brake System

The diagnosis in this manual assumes a certain level of skill and knowledge of Ford-approved diagnostic procedures.
REFER TO: Diagnostic Methods (100-00 General Information, Description and Operation).

Condition Possible Sources Action
The red brake warning indicator and the yellow ABS indicator are on. ABS Diagnostic Trouble Codes (DTCs) CHECK for ABS Diagnostic Trouble Codes (DTCs).
REFER TO: Anti-Lock Brake System (ABS) and Stability Control System (206-09 Anti-Lock Brake System (ABS) and Stability Control System, Diagnosis and Testing).
Red brake warning indicator always/never on
  • Brake Fluid Level Sensor
  • Parking Brake Switch
  • Wiring, Terminals or Connectors
  • PCM
  • BCM
REFER TO: Instrument Cluster, Message Center and Warning Chimes (413-01 Instrument Cluster, Message Center and Warning Chimes, Diagnosis and Testing).
Vehicle pulls or drifts during braking
  • Brake calipers and/or guide pins
  • Flexible brake hose
  • Brake pads
  • Brake discs
 CHECK the brake system components. INSTALL new components as necessary.
Tires
REFER TO: Wheels and Tires (204-04A Wheels and Tires, Diagnosis and Testing).
Suspension component(s) and/or wheel alignment
REFER TO: Suspension System (204-00 Suspension System - General Information, Diagnosis and Testing).
Brake pedal sinks quickly or bleeds down slowly Brake fluid leak and/or air in the system CHECK the system for leaks. REPAIR as necessary. BLEED the system.
REFER TO: Brake Bleeding (206-00 Brake System - General Information, General Procedures).
Master Cylinder PERFORM a master cylinder check — bypass condition component.
HCU
REFER TO: Anti-Lock Brake System (ABS) and Stability Control System (206-09 Anti-Lock Brake System (ABS) and Stability Control System, Diagnosis and Testing).
Brake Pedal CHECK the brake pedal simulator spring, cam and booster interface. INSTALL a new brake pedal and bracket as necessary.
Brakes lock up with light brake pedal application
  • Brake pads
  • Flexible brake hose
  • Brake Disc
  • Brake calipers and/or guide pins
 CHECK the brake system components. INSTALL new components as necessary.
ABS
REFER TO: Anti-Lock Brake System (ABS) and Stability Control System (206-09 Anti-Lock Brake System (ABS) and Stability Control System, Diagnosis and Testing).
Excessive brake pedal travel (low/spongy pedal) Brake fluid leak and/or air in the system CHECK the system for leaks. REPAIR as necessary. BLEED the system.
REFER TO: Brake Bleeding (206-00 Brake System - General Information, General Procedures).
Master Cylinder PERFORM a master cylinder check — bypass condition component.
Brake calipers and/or guide pins CHECK the brake calipers and guide pins. INSTALL new components as necessary.
Flexible brake hose CHECK the brake flex hoses during brake application. INSTALL a new brake hose if necessary.
REFER TO: Front Brake Flex Hose (206-03 Front Disc Brake, Removal and Installation).
REFER TO: Rear Brake Flex Hose (206-04 Rear Disc Brake, Removal and Installation).
Brake pedal travel is inconsistent Brake Pedal CHECK the brake pedal for binding, obstructions and correct engagement with the brake booster pushrod. REPAIR as necessary. CHECK the brake pedal mounting bolts for correct torque.
REFER TO: Brake Pedal and Bracket (206-06 Hydraulic Brake Actuation, Removal and Installation).
ABS
REFER TO: Anti-Lock Brake System (ABS) and Stability Control System (206-09 Anti-Lock Brake System (ABS) and Stability Control System, Diagnosis and Testing).
Brake drag Parking Brake Component CHECK the parking brake system.
REFER TO: Parking Brake (206-05 Parking Brake and Actuation, Diagnosis and Testing).
  • Brake Caliper and/or Guide Pins
  • Flexible brake hose
  • Brake booster
 CHECK the brake system components. INSTALL new components as necessary.
Master Cylinder PERFORM the master cylinder and compensator port component checks.
Hydraulic Control Unit (HCU)
REFER TO: Anti-Lock Brake System (ABS) and Stability Control System (206-09 Anti-Lock Brake System (ABS) and Stability Control System, Diagnosis and Testing).
Stop Lamp Switch CHECK the stop lamp switch installation.
REFER TO: Stop Lamp Switch (417-01 Exterior Lighting, Removal and Installation).
Excessive brake pedal effort
  • Insufficient Vacuum for Brake Booster Operation
  • Brake Booster Vacuum Hose
  • Brake booster
  • Brake Booster Check Valve
  • Brake Booster Vacuum Pump
 PERFORM the brake booster component checks in this section.
Brake pads CHECK the brake pads. INSTALL new components as necessary.

Symptom Chart: NVH

The diagnosis in this manual assumes a certain level of skill and knowledge of Ford-approved diagnostic procedures.
REFER TO: Diagnostic Methods (100-00 General Information, Description and Operation).

Condition Possible Sources Action
Vibration when braking
  • Brake Disc(s)/
  • Suspension Components
 GO to Pinpoint Test A
Brake Vibration/Shudder - occurs when releasing the brake pedal. Brake drag REFER TO the Symptom Chart: Brake System
Rattle noise
  • Caliper Guide Pins or Guide Pin Bolts
  • Missing or damaged anti-rattle clips or springs
  • Loose brake disc shield
  • CHECK the caliper guide pins and guide pin bolts. INSTALL new components as necessary.
  • CHECK the brake pads for missing clips or broken springs. INSTALL new components as necessary.
  • TIGHTEN the brake disc shield bolts to specification.
    REFER TO: Brake Disc Shield (206-03 Front Disc Brake, Removal and Installation).
    REFER TO: Brake Disc Shield (206-04 Rear Disc Brake, Removal and Installation).
Squeal Noise - occurs on the first (morning) brake application. Brake pads Acceptable condition. Caused by moisture and low temperature on the brake pads.
Squeal Noise - continuous squeal Brake pads CHECK the brake pads. INSTALL new components as necessary.
Squeal Noise - intermittent squeal Brake pads Acceptable condition. Caused by cold, heat, water, dirt or snow.
Moan Noise - occurs at low speeds with light brake pedal application (creep noise). Brake pads Acceptable condition.
Grinding/Groaning Noise - continuous
  • Brake pads
  • Brake Disc
 INSPECT the brake pads, brake discs and brake hardware for damage. ENSURE that the brake components are within Specifications. INSTALL new components as necessary.

Pinpoint Tests

The diagnosis in this manual assumes a certain level of skill and knowledge of Ford-approved diagnostic procedures.
REFER TO: Diagnostic Methods (100-00 General Information, Description and Operation).

Vibration when braking

Normal Operation and Fault Symptoms

Moderate and hard braking may produce HCU noise and brake pedal pulsation. Pedal pulsation combined with noise during hard braking, or on loose gravel, bumps, wet roads or snow-covered surfaces, is acceptable and indicates correct ABS operation. Brake pedal pulsation or steering wheel shudder during braking (frequency proportional to vehicle speed) indicates a brake or suspension component concern.


DIAGNOSTIC TEST A: BRAKE PEDAL VIBRATION
A1 ROAD TEST THE VEHICLE - LIGHT BRAKING
  • Road test the vehicle. Warm up the brakes by reducing vehicle speed from 80 to 32 km/h with light brake application. At highway speeds of 89 to 97 km/h, apply the brake pedal with light effort.

Is vibration/shudder felt in the steering wheel, seat or brake pedal?
Yes GO to A4
No GO to A2
A2 ROAD TEST VEHICLE – MODERATE TO HARD BRAKING
  • Road test the vehicle. At highway speeds of 89-97 km/h (55-60 mph), apply the brake pedal with moderate to hard effort.

Is vibration/shudder present?
Yes GO to A3
No The concern is not present at this time.
A3 CHECK ABS (ANTI-LOCK BRAKE SYSTEM) OPERATION
  • Road test the vehicle and brake on a dry, firm surface, then brake on a wet, snow-covered or loose surface (such as gravel).

Is vibration/shudder present only on wet, snow-covered or loose surfaces?
Yes This is normal ABS operating condition.
No GO to A5
A4 ISOLATE BRAKE VIBRATION
  • Apply the parking brake to determine whether the concern is in the front or rear brakes. At highway speeds of 89-97 km/h (55-60 mph), lightly apply the parking brake until the vehicle slows. Release the parking brake immediately after the test.

Is vibration/shudder present?
Yes GO to A7
No GO to A5
A5 CHECK THE FRONT SUSPENSION
  • Check the front suspension.

Are all suspension components in satisfactory condition?
Yes GO to A6
No REPAIR or INSTALL new components as necessary. CHECK the system for proper operation.
A6 CHECK THE FRONT BRAKE DISCS
  • INSPECT the front brake discs. MACHINE or INSTALL new brake discs as necessary.
    REFER TO: Brake Disc Machining (206-00 Brake System - General Information, General Procedures).
    REFER TO: Brake Disc (206-03 Front Disc Brake, Removal and Installation).
  • Road test the vehicle.

Is there vibration/shudder?
Yes GO to A7
No Repair is complete.
A7 CHECK THE REAR SUSPENSION
  • Check the rear suspension.

Are all suspension components in satisfactory condition?
Yes INSPECT the rear brake discs. MACHINE or INSTALL new brake discs as necessary.
REFER TO: Brake Disc Machining (206-00 Brake System - General Information, General Procedures).
REFER TO: Brake Disc (206-04 Rear Disc Brake, Removal and Installation).
No REPAIR or INSTALL new components as necessary. CHECK the system for proper operation.

Component Testing - Brake Booster

  1. Disconnect the brake booster vacuum check valve from the brake booster and connect a suitable vacuum/pressure tester to the booster side of the vacuum check valve.
  2. Apply the parking brake, start the engine and place the transmission in NEUTRAL.
    • Allow the engine to reach normal operating temperature.
  3. Verify vacuum is present at the vacuum check valve with the engine running at normal idle speed.
    • The vacuum gauge must read between 51 and 74 kPa (15-22 in-Hg).
    • If the specified vacuum is present, stop the engine, reconnect the vacuum check valve and go to step 5.
    • If the specified vacuum level is not available, go to step 4.
  4. Disconnect the vacuum check valve from the vacuum hose and verify the specified vacuum is available at the hose with the engine at idle and the transmission in NEUTRAL.
    • If the specified vacuum is present, stop the engine, install a new brake booster check valve and go to step 5.
    • For vehicles equipped with a brake vacuum pump, if the specified vacuum is not available, inspect the vacuum hose and install a new one as necessary. If the vacuum hose is in good condition, install a new brake vacuum pump.
    • For vehicles not equipped with a brake vacuum pump, if the specified vacuum is not available, stop the engine, connect the vacuum hose to the check valve and diagnose the no/low vacuum condition.
      REFER TO: Engine (303-00 Engine System - General Information, Diagnosis and Testing).
  5. Depress the brake pedal several times to release all vacuum from the system.
  6. Depress the brake pedal and hold it in the depressed position. Start the engine and verify the brake pedal moves downward after the engine starts.
    • If the brake pedal moves, the brake booster is operating correctly.
    • If the brake pedal does not move, install a new brake booster.
      REFER TO: Brake Booster (206-07 Power Brake Actuation, Removal and Installation).
  7. Run the engine at idle for a minimum of 20 seconds. Stop the engine and allow the vehicle to sit for 10 minutes, then depress the brake pedal. The brake pedal feel must be the same as with the engine running.
    • If the brake pedal is hard (no booster assist), install a new brake booster vacuum check valve and repeat the test.
    • If the condition persists, install a new brake booster.
      Refer to: Brake Booster (206-07 Power Actuated Brake, Removal and Installation).
    • If the brake pedal feels the same as with the engine running, the vacuum sensor/check valve is functioning correctly.

Component Testing — Brake Master Cylinder — Bypass Condition

  1. Inspect the brake master cylinder.
  2. Disconnect the brake tubes from the brake master cylinder.
  3. Plug the brake master cylinder outlet ports.
  4. Apply light pressure to the brake pedal and hold for 10 seconds. Release the brakes, then apply firm pressure again. If the brake pedal height cannot be corrected, the brake master cylinder has an internal leak and a new brake master cylinder must be installed.
  • If the brake pedal height is maintained, reinstall the brake tubes and tighten to specification.
    Refer to: Master Cylinder (206-06 Hydraulic Brake Actuation, Removal and Installation).
    After installation, bleed the brake system. Refer to: Brake System Bleeding (206-00 Brake System - General Information, General Procedures).

Component Testing — Brake Master Cylinder — Compensating Port

  1. Inspect the brake master cylinder.
  2. Position the vehicle on the lift in NEUTRAL.
    REFER TO: Lifting and Jacking - Overview (100-02 Jacking and Lifting, Description and Operation).
  3. Apply and release the brakes.
  4. With the brakes released, attempt to rotate each wheel and check the brakes.
  • If excessive brake drag exists on multiple wheels, go to step 5.
  • If excessive brake drag exists on only one wheel, this indicates a possible seized brake caliper, wheel brake cylinder or parking brake component. Repair or install new components as necessary.
  1. Check the brake light switch and brake pedal free play to make sure the brake pedal is not partially depressed.
  2. Loosen the brake master cylinder nuts and position the brake master cylinder away from the brake booster.
  3. With the brakes released, attempt to rotate each wheel and check the brakes.
  • If brake drag is no longer present, install a new brake booster.
    Refer to: Brake Booster (206-07 Power Actuated Brake, Removal and Installation).
  • If brake drag is still present, install a new brake master cylinder.
    Refer to: Brake Master Cylinder (206-06 Hydraulic Brake Actuation, Removal and Installation).

Test yourself

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