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For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 1998 🢒 S/T Isuzu - 4WD 🢒 Brakes 🢒 Hydraulic Brakes 🢒 Brake System Diagnosis

Brake System Diagnosis

Symptom

Causes

Excessive Braking Action
    • Vehicle loading. Refer to Loading Your Vehicle in the Vehicle Owner's Manual.
    • Leaking brake pipe, hose, or connection. Refer to Brake Fluid Leak .
    • Air in the brake system. Refer to Hydraulic Brake System Bleeding .
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling .
    • Improper rear brake adjustment. Refer to Drum Brake Adjustment in Drum Brakes.
    • Leaking wheel cylinder or caliper piston.
    • Leaking rear axle oil seal. Refer to Oil Seal and/or Bearing Replacement in Rear Drive Axle.
    • Uneven brake lining wear. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Improper thickness variation. Refer to Brake Rotor Thickness Variation Check in Disc Brakes, or to Brake System Diagnosis in Drum Brakes.
    • Excessive lateral runout. Refer to Brake Rotor Lateral Runout Check in Disc Brakes.
    • Brake assembly attachments missing or loose. Refer to Brake Pad Inspection in Disc Brakes, or to Brake Pads Replacement in Drum Brakes.
    • Leaking master cylinder (internal). Refer to Master Cylinder Diagnosis .

Excessive Brake Pedal Travel
    • Leaking brake pipe, hose, or connection. Refer to Brake Fluid Leak .
    • Leaking wheel cylinder or caliper piston.
    • Leaking rear axle oil seal. Refer to Oil Seal and/or Bearing Replacement in Rear Drive Axle.
    • Restricted brake fluid passage. Refer to Hydraulic Brake System Bleeding .
    • Excessive lateral runout. Refer to Brake Rotor Lateral Runout Check in Disc Brakes.
    • Leaking master cylinder (internal). Refer to Master Cylinder Diagnosis .
    • Damaged booster. Refer to Power Vacuum Brake Booster Replacement .

Brake Pedal Travel Gradually Increases
    • The operator is riding the brake pedal.
    • Leaking booster / vacuum system. Refer to Vacuum Brake Booster Hose Replacement .
    • Low engine vacuum. Refer to Vacuum Brake Booster Hose Replacement .
    • Vehicle loading. Refer to Loading Your Vehicle in the Vehicle Owner's Manual.
    • Restricted brake fluid passage. Refer to Hydraulic Brake System Bleeding .
    • Brake pedal or brake linkage interference (binding). Refer to Brake Pedal Replacement .
    • Rotor surface or drum surface finish. Refer to Brake Rotor Refinishing in Disc Brakes, or to Brake Drum Refinishing in Drum Brakes.
    • Contaminated brake lining. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Worn out brake lining. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Incorrect brake lining material. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Brake lining damaged by abuse. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Damaged booster. Refer to Power Vacuum Brake Booster Replacement .

Excessive Brake Pedal Effort
    • Heat spotted or scored rotors. Refer to Brake Rotor Tolerance in Disc Brakes.
    • Brake assembly attachments missing or loose. Refer to Brake Pad Inspection in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Brake lining damaged by abuse. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Worn out brake lining. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Uneven brake lining wear. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Incorrect brake lining material. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Damaged booster. Refer to Power Vacuum Brake Booster Replacement .

Brakes Slow To Respond
    • Leaking booster / vacuum system. Refer to Vacuum Brake Booster Hose Replacement .
    • Low engine vacuum. Refer to Vacuum Brake Booster Hose Replacement .
    • Brake pedal or brake linkage interference (binding). Refer to Brake Pedal Replacement .
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling .
    • Restricted brake fluid passage. Refer to Hydraulic Brake System Bleeding .
    • Sticking caliper or caliper pistons. Refer to Brake Caliper Overhaul in Disc Brakes.
    • Damaged booster. Refer to Power Vacuum Brake Booster Replacement .

Brakes Slow To Release
    • Park brake not releasing. Refer to Park Brake Cable Service/Adjustment in Park Brake.
    • Brake pedal or brake linkage interference (binding). Refer to Brake Pedal Replacement .
    • Restricted brake fluid passage. Refer to Hydraulic Brake System Bleeding .
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling .
    • Sticking caliper or caliper pistons. Refer to Brake Caliper Overhaul in Disc Brakes.
    • Damaged combination valve. Refer to Combination Valve Replacement.
    • Damaged booster. Refer to Power Vacuum Brake Booster Replacement .

Brakes Drag
    • Operator Riding the Brake Pedal.
    • Improperly Adjusted Park Brake. Refer to Park Brake Cable Service/Adjustment in Park Brake.
    • Brake pedal or brake linkage interference (binding). Refer to Brake Pedal Replacement .
    • Loose front suspension attachments. Refer to Fastener Tightening Specifications in Front Suspension.
    • Restricted brake fluid passage. Refer to Hydraulic Brake System Bleeding .
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling .
    • Sticking caliper or caliper pistons. Refer to Brake Caliper Overhaul in Disc Brakes.
    • Brake assembly attachments missing or loose. Refer to Brake Pad Inspection in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.

Uneven Braking Action (Side to Side)
    • Incorrect Tire Pressure. Refer to Tire Inflation Description in Tires and Wheels.
    • Improperly Adjusted Park Brake. Refer to Park Brake Cable Service/Adjustment in Park Brake.
    • Park brake not releasing. Refer to Park Brake Cable Service/Adjustment in Park Brake.
    • Loose front suspension attachments. Refer to Fastener Tightening Specifications in Front Suspension.
    • Improper rear brake adjustment. Refer to Drum Brake Adjustment in Drum Brakes.
    • Incorrect Front End Alignment. Refer to Wheel Alignment Specifications in Wheel Alignment.
    • Restricted brake fluid passage. Refer to Hydraulic Brake System Bleeding .
    • Worn out brake lining. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling .
    • Incorrect brake lining material. Refer to Brake Pads Replacement in Disc Brakes , or to Brake Shoe Replacement in Drum Brakes.
    • Contaminated brake lining. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Brake lining damaged by abuse. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Uneven brake lining wear. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Heat spotted or scored rotors. Refer to Brake Rotor Tolerance in Disc Brakes.
    • Brake assembly attachments missing or loose. Refer to Brake Pad Inspection in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Rotor surface or drum surface finish. Refer to Brake Rotor Refinishing in Disc Brakes, or to Brake Drum Refinishing in Drum Brakes.
    • Sticking caliper or caliper pistons. Refer to Brake Caliper Overhaul in Disc Brakes.

Uneven Braking Action (Front to Rear)
    • Vehicle Loading. Refer to Loading Your Vehicle in the vehicle Owner's Manual.
    • Leaking brake pipe, hose, or connection. Refer to Brake Fluid Leak .
    • Improperly Adjusted Park Brake. Refer to Park Brake Cable Service/Adjustment in Park Brake.
    • Air in the brake system. Refer to Hydraulic Brake System Bleeding .
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling .
    • Damaged combination valve. Refer to Combination Valve Replacement.
    • Leaking wheel cylinder or caliper piston.
    • Leaking rear axle oil seal. Refer to Oil Seal and/or Bearing Replacement in Rear Drive Axle.
    • Worn out brake lining. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Uneven brake lining wear. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Incorrect brake lining material. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Contaminated brake lining. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Brake lining damaged by abuse. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Heat spotted or scored rotors. Refer to Brake Rotor Tolerance in Disc Brakes
    • Brake assembly attachments missing or loose. Refer to Brake Pad Inspection in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Sticking caliper or caliper pistons. Refer to Brake Caliper Overhaul in Disc Brakes.
    • Rotor surface or drum surface finish. Refer to Brake Rotor Refinishing in Disc Brakes, or to Brake Drum Refinishing in Drum Brakes.
    • Restricted brake fluid passage. Refer to Hydraulic Brake System Bleeding .
    • Leaking master cylinder (internal). Refer to Master Cylinder Diagnosis .

Scraping Noise From Brakes
    • Loose front suspension attachments. Refer to Fastener Tightening Specifications in Front Suspension.
    • Brake assembly attachments missing or loose. Refer to Brake Pad Inspection in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Worn out brake lining. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Contaminated brake lining. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Brake lining damaged by abuse. Refer to Brake Pads Replacement in Disc Brakes and to Brake Shoe Replacement in Drum Brakes.
    • Uneven brake lining wear. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.

Brakes Squeak
    • Worn out brake lining. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Incorrect brake lining material. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Contaminated brake lining. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Brake lining damaged by abuse. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Uneven brake lining wear. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Heat spotted or scored rotors. Refer to Brake Rotor Tolerance in Disc Brakes.

Brakes Chatter (Roughness)
    • Brake assembly attachments missing or loose. Refer to Brake Pad Inspection in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Improper thickness variation. Refer to Brake Rotor Thickness Variation Check in Disc Brakes, or to Brake System Diagnosis in Drum Brakes.
    • Excessive lateral runout. Refer to Brake Rotor Lateral Runout Check in Disc Brakes.
    • Heat spotted or scored rotors. Refer to Brake Rotor Tolerance in Disc Brakes.
    • Leaking master cylinder (internal). Refer to Master Cylinder Diagnosis .

Brakes Groan At End Of Stop
    • Loose front suspension attachments. Refer to Fastener Tightening Specifications in Front Suspension.
    • Out-of-balance wheel assemblies. Refer to Tire Inflation Description in Tires and Wheels.
    • Rotor surface or drum surface finish. Refer to Brake Rotor Refinishing in Disc Brakes, or to Brake Drum Refinishing in Drum Brakes
    • Brake lining damaged by abuse. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.

Brake Warning Lamp ON
    • Park brake not releasing. Refer to Park Brake Cable Service/Adjustment in Park Brake.
    • Parking brake switch circuit grounded.
    • Improper rear drum brake adjustment. Refer to Drum Brake Adjustment in Drum Brakes.
    • Leaking brake pipe, hose, or connection. Refer to Brake Fluid Leak .
    • Air in the brake system. Refer to Hydraulic Brake System Bleeding .
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling .
    • Leaking wheel cylinder or caliper piston.
    • Leaking rear axle oil seal. Refer to Oil Seal and/or Bearing Replacement in Rear Drive Axle.
    • Worn out brake linings. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Uneven brake lining wear. Refer to Brake Pads Replacement in Disc Brakes, or to Brake Shoe Replacement in Drum Brakes.
    • Leaking master cylinder (internal). Refer to Master Cylinder Diagnosis .
    • Damaged combination valve. Refer to Combination Valve Replacement.