Section 06-00: Brake System, Service
1996 F-150, F-250, F-350, F-Super Duty Chassis Cab, Motorhome Chassis and Bronco Workshop Manual
DIAGNOSIS AND TESTING

Symptom Chart — Brake System Diagnosis

 
SYMPTOM CHART — BRAKE SYSTEM DIAGNOSIS
ConditionPossible SourceAction
  • Power Brake Booster Chatter, Brake Pedal Vibration
  • Slipping drive belt (F-Super Duty).
 
  • Worn brake drums.
  • REPAIR or REPLACE brake drums.
 
  • Low fluid level in power steering pump (F-Super Duty).
  • FILL brake master cylinder reservoir. CHECK for external leaks.
  • Accumulator Leaks Down; Reserve System Does Not Hold Charge (F-Super Duty)
  • Two-function valve is faulty.
  • REPLACE power brake booster.
 
  • Accumulator seal is faulty.
  • REPLACE power brake booster.
 
  • Pneumatic accumulator is faulty.
  • REPLACE power brake booster.
  • Excessive Brake Pedal Effort
  • Loose, glazed or broken drive belt (F-Super Duty).
 
  • No brake fluid in brake master cylinder reservoir.
  • FILL brake master cylinder reservoir and CHECK for external leaks. REFER to Section 06-06.
 
  • Leaks in system, power steering right turn pressure hose, power steering left turn pressure hose or power steering return hose (F-Super Duty).
  • TIGHTEN connections or REPLACE faulty parts.
 
  • Leaks at tube fittings and connections.
  • TIGHTEN fittings or REPLACE tube seats or O-rings.
 
  • Leakage at pneumatic accumulator seal (F-Super Duty).
  • REPLACE power brake booster.
 
  • Leakage at piston seal.
  • REPLACE power brake booster.
 
  • Leakage at input seal.
  • REPLACE power brake booster.
 
  • Leakage at cover-to-housing seal.
  • REPLACE power brake booster.
 
  • Leakage at spool plug seal (F-Super Duty).
  • REPLACE power brake booster.
 
  • Leakage at ball plug (F-Super Duty).
  • Unit Self-Applies (F-Super Duty)
  • Restriction in power steering return hose.
  • CLEAR or REPLACE power steering return hose.
 
  • Power steering return hose incorrectly connected.
  • CORRECT plumbing.
 
  • Dump valve faulty.
  • REPLACE power brake booster.
  • Slow Brake Pedal Return
  • Excessive seal friction in power brake booster.
 
  • Flared reaction end.
  • REPLACE power brake booster.
 
  • Broken piston return spring.
  • REPLACE power brake booster.
 
  • Restriction in power steering return line hose (F-Super Duty).
  • CLEAR or REPLACE power steering return line hose.
 
  • Power steering return line hose incorrectly connected (F-Super Duty).
  • CORRECT plumbing.
 
  • Broken spool return spring (F-Super Duty).
  • REPLACE power brake booster.
 
  • Heavy brake pedal.
  • Grabbing Brakes
  • Broken spool return spring (F-Super Duty).
  • REPLACE power brake booster.
 
  • Faulty spool action due to contamination (F-Super Duty).
  • FLUSH steering while pumping brake pedal. REFER to Section 11-00.
 
  • Damp brake shoe and linings.
 
  • Low pump flow (F-Super Duty).
  • Brake Warning Light On
  • Low brake fluid level.
  • ADD fluid, CHECK for leaks and BLEED system as required.
 
  • Ignition wiring routed too closely to fluid level indicator assembly.
  • REROUTE wiring as required.
 
  • Damaged float assembly.
  • REPAIR or REPLACE as required.
 
  • Shorted light circuit.
  • CORRECT short in warning circuit.
 
  • Worn or damaged brake fluid level indicator.
  • REPLACE brake master cylinder reservoir.
 
  • Leak in brake system.
  • REPAIR leak.
 
  • Parking brake engaged.
  • Excessive Brake Pedal Travel, Brake Pedal Feels Spongy When Fully Applied
  • Rear brakes out of adjustment.
 
  • Front wheel bearing out of adjustment.
 
  • Brake master cylinder or power brake booster dash unit mounting loose.
 
  • Front or rear disc brake caliper attachment loose.
 
  • Worn or damaged self-adjusters.
  • REMOVE brake drum and CHECK rear brake shoe and lining for proper adjustment. REPLACE brake shoe adjusting lever. REFER to Section 06-02.
 
  • Brake pedal or support improperly mounted.
 
  • Worn or damaged brake linings.
 
  • Brake drum out-of-round or front or rear disc brake rotors with excessive runout.
 
  • Worn or damaged four wheel ABS hydraulic control unit (Bronco only).
 
  • Worn or damaged RABS valve accumulator (F-Series only).
 
  • Brake tubing improperly positioned.
  • CHECK brake tubing for misposition near heat source. Fluid can boil and result in spongy pedal response.
 
  • Low brake fluid level.
  • FILL as required.
 
  • Clogged brake master cylinder filler cap hole.
  • REPAIR or REPLACE brake master cylinder filler cap.
 
  • Air in system.
  • Loss of Brake Fluid
  • Improperly positioned brake master cylinder filler cap or gasket.
  • REPOSITION cap and gasket.
 
  • Leaking brake master cylinder reservoir grommets.
  • REPLACE grommets and brake master cylinder reservoir as required.
 
  • Hydraulic system leakage.
  • Excessive Brake Pedal Effort to Fully Apply Brakes
  • Overloaded vehicle.
  • LIGHTEN load and ADVISE owner of correct load limits of vehicle.
 
  • Insufficient vacuum to power brake booster.
 
  • Restricted air filter on power brake booster.
  • CLEAN or REPLACE filter.
 
  • Power brake booster and brake pedal linkage binding caused by worn bushings or corrosion.
  • REPLACE worn brake master cylinder push rod bushing or CLEAN and LUBRICATE linkage.
 
  • Worn or damaged power brake booster.
 
  • Brake shoe and lining worn, glazed, contaminated or improper type.
  • REPLACE brake shoe and lining in axle sets.
 
  • Brake shoe and lining improperly installed.
 
  • Seized pistons in rear wheel cylinders or seized disc brake calipers.
 
  • Restricted brake lines or hoses.
  • REPAIR or REPLACE as required.
 
  • Inoperative brake load sensor proportioning valve (F-Super Duty only).
  • CHECK vehicle ride height and control linkage. REFER to Section 06-06.
  • Brake Pedal Eases Down Slowly
  • External leak.
  • REPAIR as required.
 
  • Internal leak.
  • Intermittent Loss of Brake Pedal Feel
  • Hydraulic system.
 
  • Front wheel bearings out of adjustment (on F-Super Duty vehicles, front or rear wheel bearings out of adjustment).
 
  • Drum brakes out of adjustment, worn, bad wear pattern or cracked brake drums.
 
  • Loose or improper attachment of brake pedal, pedal support, power brake booster and brake master cylinder.
 
  • Misaligned disc brake anchor plate.
  • Brakes Pull to One Side
  • Unequal air pressure in tires.
 
  • Grease or fluid on linings. Contaminated linings.
 
  • Improper size or type of lining on one wheel.
  • REPLACE with correct brake shoe and lining in sets.
 
  • Improper size rear wheel cylinder on one wheel.
  • REPLACE with correct rear wheel cylinder.
 
  • Stuck or seized pistons in rear wheel cylinders or seized disc brake calipers.
 
  • Restricted brake lines or hoses.
  • REPAIR or REPLACE as required.
 
  • Insufficient release of disc brake caliper due to lack of lubrication.
  • LUBRICATE the caliper rails and inner knuckle shoe groove (F-150 only).
 
  • Insufficient clearance of inner brake shoe.
  • Minimum clearance with brake shoe hold-down spring removed .25mm (0.01 in.) side-to-side, .71mm (0.028 in.) end-to-end. REPAIR or REPLACE as required. REFER to Section 06-02, Section 06-03 (F-150 only) or Section 06-04 (F-Super Duty only).
 
  • Front side-to-side torque variations.
  • SWAP front disc brake rotors and linings from side-to-side. If pull direction changes REPLACE pads and TAKE light cut off front disc brake rotors. REFER to Section 06-03.
 
  • Worn or damaged rear brake.
  • CHECK for contaminants, broken components, seized parking brake and improperly installed parts. REPAIR or REPLACE as required. REFER to Section 06-02.
 
  • Incorrectly adjusted rear brake shoe and lining.
 
  • Other brake components.
      Improper adjustment of drum brakes.Improper positioning of disc brake pad and lining in the disc brake caliper.Improperly adjusted, damaged or worn wheel bearings.Distorted rear brake shoe and lining.Worn brake linings.Missing, broken or stretched retracting or retaining springs and clips.
  • INSPECT, ADJUST, REPAIR or REPLACE as required. REFER to applicable Section in Group 06.
  • GO to Pinpoint Test A.
 
  • Other components.Suspension.Steering.Tires.
  • REFER to the appropriate section in Group 04 or Group 11.
  • Brakes Grab or Lock Up When Applied
  • ABS HCU: defective outlet (dump) valve (Bronco ONLY).
 
  • RABS Valve: defective outlet (dump) valve (F-150, F-250, F-350).
 
  • Brake load sensor proportioning valve or linkage binding, out of adjustment or defective.
  • Brakes Drag, Slow or Incomplete Release
  • Parking brake levers binding.
  • REPAIR, LUBRICATE or REPLACE parts as required. REFER to Section 06-05.
 
  • Brake pedal binding.
  • REPAIR, LUBRICATE or REPLACE parts as required.
 
  • Front wheel bearing out of adjustment.
 
  • Worn or damaged brake master cylinder.
  • CHECK brake master cylinder for damage. REPAIR or REPLACE. REFER to Section 06-06.
 
  • Brakes out of adjustment.
  • ADJUST brakes.
 
  • Restriction in hydraulic system.
 
  • Seized rear wheel cylinders or disc brake calipers.
 
  • Stoplight switch out of adjustment.
 
  • Lack of lubricant on front disc brake caliper slides.
  • LUBRICATE front disc brake caliper slides.
 
  • Speed control dump solenoid inoperative.
 
  • Hydraulic power Hydro-Boost (F-Super Duty and Motorhome Stripped Chassis) system restricted or routed incorrectly.
 
  • Brake pedal to bell crank rod adjusted incorrectly (F-Super Duty Motorhome Chassis).
  • Noise at Wheels When Brakes Are Applied — Snap or Clicks
  • Cracked welds at rear brake shoe web.
 
  • Rear brake shoe and lining binding at backing plate ledges.
  • CLEAN and LUBRICATE ledges.
 
  • Machining marks on brake drums.
  • REFINISH or REPLACE brake drums.
 
  • Brake backing plate ledges worn.
  • REPLACE brake backing plate and LUBRICATE ledges.
 
  • On disc brakes — loose or missing anti-rattle clips.
 
  • Improper finish on brake rotor.
  • REFINISH front disc brake rotor.
  • Noise at Wheels — Brakes Applied — Squeak or Squeal
  • Rear brake shoe and lining and/or front disc brake rotor surface contamination.
  • REMOVE disc brake caliper from front wheel spindle and REMOVE inner and outer linings. HAND SAND the linings and both braking surfaces of rotor using Garnett Paper 100A (medium grit) or equivalent or aluminum oxide 150J (medium) or equivalent. REFER to Section 06-03 or Section 06-04.
 
  • Improper lining parts.
 
  • Brake drums — damaged or incorrect brake shoe retracting springs, loose or damaged shoe retainer pins, springs and clips, and grooved backing plate ledges.
 
  • Worn lining indicators.
  • INSPECT, REPLACE lining in axle sets.
  • Noise at Wheels — Brakes Not Applied — Squeak or Squeal
  • Wheel covers improperly attached.
  • SEAT the wheel covers with a rubber mallet. REPAIR flanges or REPAIR cover. REFER to Section 04-04.
 
  • Loose lug nuts.
  • TIGHTEN to specified torque. REPLACE wheel if stud holes are elongated.
 
  • Worn, dry or improperly adjusted wheel bearings.
 
  • Bent or warped brake backing plate or rotor shield causing interference with brake drum or front disc brake hub and rotor.
 
  • Contaminated linings — adjustment too tight (rear brakes).
  • REMOVE contamination or REPLACE linings. ADJUST brakes properly.
 
  • Improper machining of drum, causing interference with backing plate or shoe.
  • REFINISH brake drum or FILE off material contacting brake backing plate as needed. REFER to Section 06-02.
 
  • Other brake system components:Loose or extra parts in brakes.Drum brakes — weak, damaged or incorrect retracting springs.Drum brakes — grooved backing plate ledges.Improper positioning of pad in disc brake caliper.Outside diameter of front disc brake rotor rubbing front disc brake caliper housing.Lack of correct lubricant on disc brake caliper slides and pins.Improper installation of brake shoe hold-down spring.Excessive runout of front disc brake rotor.
  • Noise at Wheels When Brakes Are Applied — Scrape or Grind (Loud, Harsh Rubbing Noise)
  • Contaminated linings — if caliper is not bound, brake linings are not worn to the steel plate, and rotor is scored at least 13mm (0.5-inch) wide by 1.5mm (1/16-inch) deep.
  • REPLACE or TURN front disc brake rotor. REMOVE and REPLACE contaminated lining as required. REFER to Section 06-03 or Section 06-04.
 
  • Wheel bearings not lubricated. Verify noise is coming from bearings.
 
  • Worn brake linings or foreign material between lining and brake drum or front disc brake rotor.
 
  • Brake shoe interference with back of brake drum, or shield-to-rotor clearance also binding at backing plate guide ledges.
  • INSPECT. REPLACE as required. LUBRICATE guide ledges.
 
  • Caliper to wheel or rotor interference.
  • REPLACE as required.
 
  • Other brake system components:Warped or bent backing plate or splash shield causing interference with brake drum.Cracked drums or rotors.
 
  • Tires rubbing against chassis or body.
 
  • Rotor to spindle interference.
  • Noise at Wheels — Brakes Applied — Groan, Roughness or Chatter at Wheel; A Harsh Feeling While Braking in Neutral Evidenced by a Pulsating Brake Pedal Feel
  • Loose lug nuts.
  • TIGHTEN to specified torque. REPLACE wheel if stud holes are elongated. REFER to Section 04-04.
 
  • Contaminated disc brake rotor or lining surfaces.
 
  • Worn, damaged, dry or improperly adjusted wheel bearings.
 
  • Loose or worn front suspension components.
  • INSPECT, REPAIR or REPLACE as required.
 
  • Disc brake rotor thickness variation.
 
  • Disc brake caliper anchor plate loose or missing parts. Also, loose or bent disc brake rotor shield.
 
  • Rear brake roughness.
  • ATTEMPT stopping the vehicle using the parking brake. If roughness is present, CHECK brake drums for excessive wear or runout. REFINISH or REPLACE as required. REFER to Section 06-02.
 
  • Brake drum cracked or out-of-round.
  • REFINISH or REPLACE brake drum as required. REFER to Section 06-02.
 
  • Wheel/tire imbalance.
 
  • Drivetrain imbalance.
  • ATTEMPT stopping the vehicle in the neutral transmission position. If roughness is gone, drivetrain should be inspected.
  • Noise at Wheels — Brakes Not Applied — Growling, Click, Rattle, Clunk or Knock. Defined by a Series of Sharp, Short Sounds in Quick Succession
  • Stones or foreign material trapped inside.
  • REMOVE stones or foreign material as required.
 
  • Loose wheel lug nuts.
  • TIGHTEN to specified torque. REPLACE wheel if stud holes are elongated. REFER to Section 04-04.
 
  • Worn, damaged or dry wheel bearings.
 
  • Disc brake caliper loose or missing anti-rattle clips.
 
  • Drum brakes loose or extra parts.
 
  • Front disc brake rotor shield bent, loose or missing.
  • REPAIR as REQUIRED.
 
  • Loose grease cap.
  • REPAIR or REPLACE as required.
 
  • Drum brakes — rear brake shoe and lining binding at backing plate ledges.
  • LUBRICATE ledges.
 
  • Drum brakes — backing plate ledges worn.
  • REPLACE brake backing plate and LUBRICATE ledges.
  • Vibration When Brakes Are Applied — Front Brakes
  • Loose lug nuts.
  • TIGHTEN lug nuts to specification. REPLACE wheel if stud holes are elongated. REFER to Section 04-04.
 
  • Cracked front disc brake rotor.
 
  • Front disc brake rotor out-of-round or improper machining.
  • MACHINE front disc brake rotor or REPLACE as required.
 
  • Excessive front disc brake rotor runout.
  • REPLACE front disc brake rotor.
 
  • Excessive front disc brake rotor thickness variation.
  • REPLACE front disc brake rotor.
 
  • Worn or improperly adjusted wheel bearings.
  • ADJUST or REPLACE wheel bearings as required. REFER to the applicable section in Group 05.
 
  • Loose or worn front suspension components.
  • TIGHTEN loose components to specifications. REPLACE worn or damaged components. REFER to Group 04.
 
  • Excessive radial or lateral runout on wheel and tire assembly.
  • Vibration When Brakes Are Applied — Brake Drums
  • Loose lug nuts.
  • TIGHTEN lug nuts to specification. REPLACE wheel if stud holes are elongated. REFER to Section 04-04.
 
  • Cracked brake drum.
 
  • Brake drum out-of-round or improperly machined.
  • MACHINE drums or REPLACE as required.
 
  • Excessive radial and lateral runout on wheel and tire assembly.
  • ADJUST tires or wheel to eliminate runout or REPLACE wheel and/or tire as required.
  • GO to Pinpoint Test C.
  • Parking Brake Will Not Hold
  • Parking brake cable out of adjustment.
 
  • Rear brakes out of adjustment.
 
  • Parking brake linkage, cable, parking brake control, clevis or ratchet binding, worn or damaged.
  • REPAIR or REPLACE linkage or parking brake cables as required. REFER to Section 06-05.
  • Parking Brake Will Not Release or Fully Return
  • Manual release brake control components binding or damaged.
  • REPAIR or REPLACE manual parking brake control.
 
  • Parking brake linkage and cables binding.
 
  • Worn or damaged rear brake components.
  • CHECK brake shoe retracting springs and parking brake levers. REPAIR as required. REFER to Section 06-02.
  • Rough Engine Idle or Stall
  • Vacuum leak.
  • CHECK vacuum booster hoses and connections for leaks. REPAIR or REPLACE as required.
 
  • Worn or damaged power brake booster.
  • CHECK power brake booster for internal leaks. REPLACE if required. REFER to Section 06-06.
  • No or Low Vacuum
  • Loose vacuum pump drive belt.
 
  • Vacuum pump is locked up.
 
  • No vacuum from pump outlet.
 
  • Outlet manifold assembly outlet port.
 
  • Defective or worn vacuum hoses.
  • REPLACE as necessary.