Initial Inspection and Diagnostic Overview
Inspection and VerificationWARNING: Use of any brake fluid other than the approved DOT 3 will cause permanent damage to brake components and will render the brakes inoperative. Failure to follow these instructions may result in personal injury.
WARNING: Carefully read cautionary information on product label. For EMERGENCY MEDICAL INFORMATION seek medical advice. In the USA or Canada on Ford/Motorcraft products call: 1-800-959-3673. For additional information, consult the product Material Safety Data Sheet (MSDS) if available. Failure to follow these instructions may result in personal injury.
CAUTION: Brake fluid is harmful to painted and plastic surfaces. If brake fluid is spilled onto a painted or plastic surface, immediately wash it with water.
NOTE: Always check the fluid level in the brake master cylinder reservoir before carrying out the test procedures. If the fluid level is not at the correct level, clean the reservoir cap before removing, then add clean, specified brake fluid.
NOTE: Prior to carrying out any diagnosis, make sure the red brake warning indicator is functional. Refer to Instrument Panel, Gauges and Warning Indicators.
The first indication that something may be wrong in the brake system is a change in the feeling through the brake pedal. The brake warning indicator in the instrument cluster and the brake fluid level 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 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 concern. 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.
Road Test
The technician should have a thorough knowledge of the brake system operation and accepted general braking guidelines in order to detect any 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.
For low or spongy brake pedal concerns:
^ bleed the brake system and retest the brake pedal feel.
^ if the brake pedal is still low or feels spongy, check the brake pedal mounting for looseness and incorrect installation. Check the brake booster and the brake master cylinder for loose mounting. Correct as necessary and retest the system for normal operation.
^ check the fluid level. The fluid level must be at or above the minimum mark. If the fluid level is below the minimum mark, check the system for leaks.
For a slow or incomplete brake pedal return concern:
^ inspect for binding, damage, incorrect installation or interference at the brake pedal.
^ check the brake booster for binding, damage and incorrect installation.
Brake Pads
NOTE: New brake pads are not required if friction material properties are within guidelines. New brake pads are not required when the brake discs are machined.
^ Remove the brake pads.
^ Inspect and measure the thickness of the brake pad friction material.
- Install new brake pads if the thickness of the friction material is less than 3.0 mm (0.118 inch).
- Compare all 4 front or rear pads for uneven wear. Install new brake pads if the thickness of the friction material varies from pad to pad by more than 2.0 mm (0.079 inch).
- Install new brake pads if there are missing chunks or cracks in the lining through to the backing plate.
- If the friction material shows taper wear (i.e. the thickness varies by more than 3.0 mm [0.118 inch] in any direction), or if the pads show uneven wear (2.0 mm [0.079 inch] difference between the inboard and the outboard pad), verify the caliper guide pins are functioning correctly.
Brake Discs
CAUTION: Using an impact tool without a torque socket leads to unevenly tightened wheel nuts. This causes brake disc on-vehicle lateral runout and brake roughness.
NOTE: It is generally not required to install new brake discs to address noise issues.
^ Remove the brake disc.
^ Inspect the brake discs and measure the brake disc thickness in a minimum of 4 places around the circumference of the brake disc. Record the measurements.
- Install new brake discs if any thickness measurement is less than the minimum specification.
- Install new brake discs if cracked.
- Machine the brake discs if the diagnosis has revealed vibration in the steering wheel, seat, or pedal while braking. Heavily scored brake discs, similar to that caused by pads worn down to the backing plate, should also be machined. In order to machine, discs must be above the minimum thickness to machine specification.
Brake Caliper
Inspect the brake calipers for:
^ brake fluid leaks.
^ torn or cracked boots and seals.
^ bound or corroded caliper piston.
^ correct guide pin operation.
Brake Caliper Guide Pins
CAUTION: Do not use power tools for caliper guide pin bore cleaning.
The guide pins should slide with a reasonable amount of hand force. If the brake pads show taper wear or the guide pins are difficult to move, carry out these steps.
NOTE: If a guide pin kit is not available, install a new caliper assembly.
^ Disassemble the guide pins.
^ Use a wire brush, rolled-up sandpaper or emery cloth to remove all corrosion and foreign material from the caliper guide pin bores. Clean remaining foreign material from the bores with brake parts cleaner and compressed air.
^ Install new brake pads if the lining is not within specifications.
^ Assemble the caliper guide pins using new caliper seals, boots and guide pins. Use an ample amount of grease to lubricate the bores and guide pins.
Brake Hoses and Tubes
CAUTION: Never use copper tubing. It is subject to fatigue, cracking and corrosion, which could result in brake tube failure.
^ Double-wall steel tubing is used throughout the brake hydraulic system. All brake tube fittings must be correctly double flared to provide strong, leakproof connections. When bending tubing to fit the underbody or rear axle contours, be careful not to kink or crack the tube.
^ If a section of the brake tube is damaged, the entire section must be installed new with a tube of the same type, size, shape and length.
^ When installing the hydraulic brake tubing, hoses or connectors, tighten all connections to specifications. After installation, bleed the brake system.
^ The wet appearance on the outer cover of rubber brake hoses is called sweating. This is a normal condition for neoprene rayon-braided hose and is not a sign of leakage or cause to install a new hose.
Install a new flexible brake hose if the hose shows signs of softening, cracking or other damage.
When installing a new brake hose, position the hose to avoid contact with other vehicle components.
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 under these conditions:
^ Missing or poorly-fitted brake master cylinder filler cap
^ Punctured or otherwise damaged brake master cylinder reservoir
^ Missing or damaged brake master cylinder filler cap gasket
^ Missing, damaged or poorly-fitted sealing grommets between the brake master cylinder and the brake master cylinder reservoir.
The brake master cylinder reservoir grommets are not repairable and must be installed new as part of a new brake master cylinder reservoir.
Brake Master Cylinder - Normal Conditions
These 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 rises during brake application and falls during release. The net fluid level (such as after brake application and release) remains unchanged.
Condition 2: A trace of brake fluid exists 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 decreases 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. Symptom Related Diagnostic Procedures
Brake Booster
Inspect the brake booster:
^ for excessive corrosion or damage.
^ vacuum connections for leakage.
^ vacuum hoses for kinks or leakage.
^ check valve for correct operation.
Changes in the brake pedal feel or travel are indicators that something could be wrong in the brake system. GO to Symptom Chart for abnormal condition diagnosis. Symptom Related Diagnostic Procedures
Parking Brake
Check the operation of the parking brake system with the vehicle on a hoist and the parking brake control fully released. Check for any damaged cables and install new components as necessary. Check the rear brake adjustment or carry out the brake system diagnosis.
Adjustable Pedal With or Without Memory Feature
1. Verify the customer concern.
2. Visually inspect for obvious signs of mechanical or electrical damage.
Visual Inspection Chart
Visual Inspection Chart:
3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
4. For adjustable pedals without memory, if the cause is not visually evident, GO to Symptom Chart. Symptom Related Diagnostic Procedures
5. NOTE: Make sure to use the latest scan tool software release.
For adjustable pedals with memory, if the cause is not visually evident, connect the scan tool to the data link connector (DLC).
6. NOTE: The vehicle communication module (VCM) LED prove out confirms power and ground from the DLC are provided to the VCM.
If the scan tool does not communicate with the VCM:
^ Check the VCM connection to the vehicle.
^ Check the scan tool connection to the VCM.
^ Refer to Information Bus (Module Communications Network), No power to the scan tool, to diagnose no communication with the scan tool.
7. If the scan tool does not communicate with the vehicle:
^ Verify the ignition key is in the ON position.
^ Verify the scan tool operation with a known good vehicle.
^ Refer to Information Bus (Module Configuration) to diagnose no response from the powertrain control module (PCM).
8. Carry out the network test.
^ If the scan tool responds with no communication for one or more modules, refer to Information Bus (Multiplex Communications Network).
^ If the network test passes, retrieve and record continuous memory diagnostic trouble codes (DTCs).
9. Clear the continuous DTCs and carry out the self-test diagnostics for the driver seat module (DSM).
10. If the DTCs retrieved are related to the concern, go to the Driver Seat Module (DSM) Diagnostic Trouble Code (DTC) Index. For all other DTCs, refer to Body Control Systems (Multifunction Electronic Control Module). Driver Seat Module (DSM) Diagnostic Trouble Code (DTC) Index
11. If no DTCs related to the concern are retrieved, GO to Symptom Chart. Symptom Related Diagnostic Procedures