Lincoln Navigator: Brake System - General Information / Brake System. Diagnosis and Testing

Normal Operation and Fault Conditions

During moderate to heavy braking, noise from the HCU and pulsation in the brake pedal can be observed. Pedal pulsation coupled with noise during heavy braking or on loose gravel, bumps, wet or snowy surfaces is acceptable and indicates correct functioning of the ABS . Pedal pulsation or steering wheel nibble when the brakes are applied (frequency is proportioned to the vehicle speed) indicates a concern with a brake or suspension component.

Possible Sources

• Brake disc(s)
• Suspension components
• Brake pads

• Road test the vehicle. Warm the brakes by slowing the vehicle from 80 to 32 km/h (50 to 20 mph) using light brake force. At highway speeds of 89-97 km/h (55-60 mph), apply the brake using light pedal force.

• Road test the vehicle. At highway speeds of 89-97 km/h (55-60 mph), apply the brake using a moderate to heavy pedal force.

NOTE: During normal operation, brake pedal is not connected to brake callipers, instead, it is connected to a pedal feel simulator inside the EBB thru brake fluid, the pedal feel simulator is a springing system which provides feedback to driver’s foot. Pedal pulsation will not be felt during ABS operation.

• Road test the vehicle and apply the brakes on a dry, firm surface, then apply the brakes on a wet, snowy or loose surface (such as gravel).

• Check the front suspension.

• Inspect the front brake discs.
  REFER to: Specifications (206-00 Brake System - General Information, Specifications).
  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.

• Check the rear suspension.

Normal Operation and Fault Conditions

During braking, the vehicle should stop quickly from an initial pedal press and in a straight line. Some- times, the vehicle pulls to one side or the other while braking. This indicates there is a concern with a brake or suspension component.

Possible Sources

• Brake calipers and/or guide pins
• Brake flexible hose
• Brake pads
• Brake discs
• Tires
• Suspension component(s) and/or wheel alignment

• Verify that there are no loose or damaged components.

• Verify that there are no damaged components, uneven tire wear.

• Check the suspension components.

• Check suspension alignment.

Normal Operation and Fault Conditions

The brake pedal is connected to the EBB . When the brake pedal is pressed, the EBB generates brake pressure, based on the driver demand, and brake fluid is pushed through the double-walled steel tubes and flexible hoses to the front and rear disc brake calipers. The brake fluid enters the disc brake calipers, forcing the caliper pistons and brake pads outward against the brake disc friction surface, slowing or stopping rotation. When the brake pedal is released, brake fluid pressure is relieved, returning the front and rear disc brake caliper pistons and brake pads to the unapplied position. If the brake pedal goes down fast or eases down slowly, it indicates there is a concern with the brake system.

Possible Sources

• Brake fluid leaks and/or air in the system
• ABS / HCU

• Verify that there are no loose or damaged components.

• Inspect the system for leaks.

• Inspect the system for air.

Normal Operation and Fault Conditions

The brake pedal is connected to the EBB . When the brake pedal is pressed, the EBB generates brake pressure, based on the driver demand, and brake fluid is pushed through the double-walled steel tubes and flexible hoses to the front and rear disc brake calipers. The brake fluid enters the disc brake calipers, forcing the caliper pistons and brake pads outward against the brake disc friction surface, slowing or stopping rotation. When the brake pedal is released, brake fluid pressure is relieved, returning the front and rear disc brake caliper pistons and brake pads to the unapplied position. The brakes can lock up during application due to overheating or faulty components. This condition indicates there is a concern with the brake system.

Possible Sources

• Brake pads
• Brake flexible hose
• Brake discs
• Brake calipers and/or guide pins
• ABS / HCU

• Inspect the brake system components.

• Ignition ON.

• Using a diagnostic scan tool, perform the ABS self-test.

Normal Operation and Fault Conditions

The brake pedal is connected to the EBB . When the brake pedal is pressed, the EBB generates brake pressure, based on the driver demand, and brake fluid is pushed through the double-walled steel tubes and flexible hoses to the front and rear disc brake calipers. The brake fluid enters the disc brake calipers, forcing the caliper pistons and brake pads outward against the brake disc friction surface, slowing or stopping rotation. When the brake pedal is released, brake fluid pressure is relieved, returning the front and rear disc brake caliper pistons and brake pads to the unapplied position. Leaks and/or air in the system can cause a spongy brake pedal and loss of braking in the vehicle. This condition indicates there is a concern with the brake system.

Possible Sources

• Brake fluid leaks and/or air in the system
• ABS / HCU
• Brake calipers and/or guide pins
• Brake flexible hose

• Inspect the system for leaks.

• Inspect the system for air.

• Inspect the front and rear brake discs and brake pads.
  • 
    REFER to: Specifications (206-00 Brake System - General Information, Specifications).
    . MACHINE or INSTALL new brake discs as necessary.
  • Install new front brake pads 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).
    REFER to: Brake Pads (206-03 Front Disc Brake, Removal and Installation).
    
  • Install new rear brake pads 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).
    REFER to: Brake Pads (206-04 Rear Disc Brake, Removal and Installation).
    

• Inspect the brake calipers and guide pins.

• Inspect the brake flexible hoses during brake application.

Normal Operation and Fault Conditions

The brake pedal is connected to the EBB . When the brake pedal is pressed, the EBB generates brake pressure, based on the driver demand, and brake fluid is pushed through the double-walled steel tubes and flexible hoses to the front and rear disc brake calipers. The brake fluid enters the disc brake calipers, forcing the caliper pistons and brake pads outward against the brake disc friction surface, slowing or stopping rotation. When the brake pedal is released, brake fluid pressure is relieved, returning the front and rear disc brake caliper pistons and brake pads to the unapplied position. If the brake pedal goes down fast or eases down slowly, it indicates there is a concern with the brake system.

Possible Sources

• Brake pedal
• ABS / HCU

• Inspect the brake pedal for binding, obstructions and correct interface to booster rod.

Normal Operation and Fault Conditions

The brake pedal is connected to the EBB . When the brake pedal is pressed, the EBB generates brake pressure, based on the driver demand, and brake fluid is pushed through the double-walled steel tubes and flexible hoses to the front and rear disc brake calipers. The brake fluid enters the disc brake calipers, forcing the caliper pistons and brake pads outward against the brake disc friction surface, slowing or stopping rotation. When the brake pedal is released, brake fluid pressure is relieved, returning the front and rear disc brake caliper pistons and brake pads to the unapplied position. The vehicle will experience dragging if the brake fluid pressure is not relieved or the brake pads do not return to the unapplied condition. This condition indicates there is a concern with the brake system.

Possible Sources

• Parking brake component
• Brake caliper and/or guide pins
• Brake flexible hose
• ABS / HCU
• Check brake fluid level in reservoir

• Inspect the parking brake system.

• Inspect the brake calipers and guide pins.

Normal Operation and Fault Conditions

The brake pedal is connected to the EBB . When the brake pedal is pressed, the EBB generates brake pressure, based on the driver demand, and brake fluid is pushed through the double-walled steel tubes and flexible hoses to the front and rear disc brake calipers. The brake fluid enters the disc brake calipers, forcing the caliper pistons and brake pads outward against the brake disc friction surface, slowing or stopping rotation. When the brake pedal is released, brake fluid pressure is relieved, returning the front and rear disc brake caliper pistons and brake pads to the unapplied position. The brake booster provides assistance to the pedal effort applied by the driver. If excessive pedal effort is required while applying the brakes, it indicates there is a concern within the brake system.

Possible Sources

• Brake pads
• ABS / HCU

• Ignition ON.

• Using a diagnostic scan tool, CARRY OUT the PCM self- test. DIAGNOSE all PCM Diagnostic Trouble Codes (DTCs).

• Inspect the brake pads.

Normal Operation and Fault Conditions

Some squealing noise from the brake system is acceptable under certain conditions such as cold start or low speed brake application. Under all other general driving conditions, the vehicle must come to a stop on brake application and the brake system operation must not create noise. A rattling noise from the brakes indicate a concern with the brake system.

Possible Sources

• Caliper guide pins or guide pin bolts
• Missing or damaged anti-rattle clips or springs
• Loose brake disc shield

• Inspect the caliper guide pins and guide pin bolts.

• Inspect anti-rattle clips or springs for missing or damage.

• Inspect brake disc shield and bolts.

Normal Operation and Fault Conditions

During driving, there should not be any squealing noise except while cold start, low speed and intermittent. A continuous squealing noise from the brakes indicates a concern with the brake system.

Possible Sources

• Brake pads

• Perform a road test and confirm the concern.

• Is the squealing noise:
  • upon cold start
  • at low speeds
  • intermittent

• Perform a road test and confirm the concern.

Normal Operation and Fault Conditions

Some squealing noise from the brake system is acceptable under certain conditions such as cold start or low speed brake application. Under all other general driving conditions, the vehicle must come to a stop on brake application and the brake system operation must not create noise. A groaning noise from the brake system at low vehicle speeds or light application of the brake pedal indicates a concern with the brake system.

Possible Sources

• Brake pads

• Ignition ON.

• Perform a road test, apply brake lightly at low speeds and check groaning noise.

Normal Operation and Fault Conditions

Some squealing noise from the brake system is acceptable under certain conditions such as cold start or low speed brake application. Under all other general driving conditions, the vehicle must come to a stop on brake application and the brake system operation must not create noise. A continuous grinding or moaning noise from the brake system on application of the brakes indicates a concern with the brake system.

Possible Sources

• Brake pads
• Brake disc

• Ignition ON.

• Perform a road test, apply brake and check groaning noise.