GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC Suburban - 4WD 🢒 Brakes 🢒 Hydraulic Brakes 🢒 Brake System Diagnosis

Belt Tension

When servicing any part of the brake system, check the power steering pump belt for the following conditions:

    • Improper belt tension
    • Wear

The serpentine belt is not adjustable. Refer to Drive Belt Diagnosis in Engine Cooling.

Power Steering Fluid Level

When servicing any part of the brake system, check the fluid level in the power steering fluid reservoir. Check the fluid level at regular intervals. Add fluid as needed. Refer to Checking and Adding Power Steering Fluid Power Steering System.

Brake System Diagnosis

Symptom

Causes

Excessive Brake Pedal Travel
    • Leaking brake pipe, hose, or connection. Refer to Brake Fluid Leak
    • Leaking piston seal. Refer to Seal Leak Diagnosis
    • Leaking master cylinder (internal). Refer to Master Cylinder Diagnosis
    • Air in brake system. Refer to Hydraulic Brake System Bleeding
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling
    • Improper thickness variation. Refer to Brake Rotor Thickness Variation Check in Disc Brakes, or Brake Drum Inspection in Drum Brakes.
    • Uneven brake lining wear. Refer to Brake Pad Inspection in Disc Brakes, or to Brake Shoe Inspection 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 Brake Shoe Inspection in Drum Brakes.

Brake Pedal Travel Gradually Increases
    • Leaking brake pipe, hose, or connection. Refer to Brake Fluid Leak
    • Leaking piston seal. Refer to Seal Leak Diagnosis
    • Leaking master cylinder (internal). Refer to Master Cylinder Diagnosis
    • Restricted Passage in the Vacuum Booster. Refer to Vacuum Booster Diagnosis
    • Damaged Vacuum Booster System. Refer to Vacuum Booster Diagnosis
    • Restricted Brake Fluid Passage. Refer to Hydraulic Brake System Bleeding

Excessive Brake Pedal Effort
    • Leaking Booster/Vacuum System. Refer to Vacuum Brake Booster Hose Replacement
    • Restricted Passage in the Vacuum Booster. Refer to Vacuum Booster Diagnosis
    • Damaged Vacuum Booster System. Refer to Vacuum Booster Diagnosis
    • Worn Out Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Glazed Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Incorrect Brake Lining Material. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Contaminated Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Brake Lining Damage By Abuse. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Restricted Brake Fluid Passage. Refer to Hydraulic Brake System Bleeding
    • Brake Pedal or Brake Linkage Interference (Binding). Refer to Brake Pedal Replacement
    • Operator Riding the Brake Pedal.

Excessive Braking Action
    • Damaged Vacuum Booster System. Refer to Vacuum Booster Diagnosis
    • Worn Out Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Uneven brake lining wear. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Incorrect Brake Lining Material. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Brake Lining Damage By Abuse. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Rotor Surface or Drum Surface Finish. Refer to Brake Rotor Refinishing in Disc Brakes, or Brake Drum Refinishing, 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 Brake Shoe Inspection in Drum Brakes.

Brakes Slow To Respond
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling
    • Leaking Vacuum System. Refer to Brake Hose and Pipe Diagnosis
    • Restricted Passage in the Vacuum Booster. Refer to Vacuum Booster Diagnosis
    • Damaged Vacuum Booster System. Refer to Vacuum Booster Diagnosis
    • Glazed Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Restricted Brake Fluid Passage. Refer to Hydraulic Brake System Bleeding
    • Brake Pedal or Brake Linkage Interference (Binding). Refer to Brake Pedal Replacement
    • Sticking Caliper or Caliper Pistons. Refer to Brake Caliper Inspection

Brakes Slow To Release
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling
    • Restricted Passage in the Vacuum Booster. Refer to Vacuum Booster Diagnosis
    • Damaged Vacuum Booster System. Refer to Vacuum Booster Diagnosis
    • Restricted Brake Fluid Passage. Refer to Hydraulic Brake System Bleeding
    • Brake Pedal or Brake Linkage Interference (Binding). Refer to Brake Pedal Replacement
    • Sticking Caliper or Caliper Pistons. Refer to Brake Caliper Inspection in Disc Brakes.
    • Parking Brake not Releasing. Refer to Park Brake Cable Service/Adjustment in Parking Brake.

Brakes Drag
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling
    • Brake Assembly Attachments Missing or Loose. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Restricted Brake Fluid Passage. Refer to Hydraulic Brake System Bleeding
    • Improperly adjusted Stoplamp Switch. Refer to Stop Lamp Switch Replacement
    • Improperly adjusted Cruise Control Vacuum Dump.
    • Brake Pedal or Brake Linkage Interference (Binding). Refer to Brake Pedal Replacement
    • Improperly Adjusted Parking Brake. Refer to Park Brake Cable Service/Adjustment in Parking Brakes.
    • Loose Front Suspension Attachments. Refer to Fastener Tightening Specifications in Front Suspension.
    • Operator Riding the Brake Pedal.
    • Sticking Caliper or Caliper Pistons. Refer to Brake Caliper Inspection

Uneven Braking Action (Side to Side)
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling
    • Worn Out Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Uneven Brake Lining Wear. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Glazed Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Incorrect Brake Lining Material. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Contaminated Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Brake lining Damage By Abuse. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Heat Spotted or Scored Rotors. Refer to Brake Rotor Tolerance
    • Brake Assembly Attachments Missing or Loose. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Restricted Brake Fluid Passage. Refer to Hydraulic Brake System Bleeding
    • Incorrect Front End Alignment. Refer to Wheel Alignment Specifications
    • Incorrect Tire Pressure. Refer to Tire Inflation Description
    • Loose Front Suspension Attachments. Refer to Fastener Tightening Specifications in Front Suspension.
    • Sticking Caliper or Caliper Pistons. Refer to Brake Caliper Inspection
    • Parking Brake not Releasing. Refer to Park Brake Cable Service/Adjustment in Parking Brake.

Uneven Braking Action (Front to Rear)
    • Leaking brake pipe, hose, or connection. Refer to Brake Fluid Leak
    • Leaking piston seal. Refer to Seal Leak Diagnosis
    • Leaking master cylinder (internal). Refer to Master Cylinder Diagnosis
    • Air in brake system. Refer to Hydraulic Brake System Bleeding
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling
    • Worn Out Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Uneven Brake Lining Wear. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Glazed Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Incorrect Brake Lining Material. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Contaminated Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Brake lining Damage By Abuse. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Heat Spotted or Scored Rotors. Refer to Brake Rotor Tolerance
    • Brake Assembly Attachments Missing or Loose. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Restricted Brake Fluid Passage. Refer to Hydraulic Brake System Bleeding
    • Improperly Adjusted Parking Brake. Refer to Park Brake Cable Service/Adjustment in Parking Brake.
    • Sticking Caliper or Caliper Pistons. Refer to Brake Caliper Inspection

Scraping Noise From Brakes
    • Worn Out Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Uneven Brake Lining Wear. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Contaminated Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Brake lining Damage By Abuse. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Brake Assembly Attachments Missing or Loose. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Loose Front Suspension Attachments. Refer to Fastener Tightening Specifications in Front Suspension.

Brakes Squeak Without Application
    • Worn Out Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Uneven Brake Lining Wear. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Glazed Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Incorrect Brake Lining Material. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Contaminated Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Brake lining Damage By Abuse. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Heat Spotted or Scored Rotors. Refer to Brake Rotor Tolerance

Brakes Squeak During Application
    • Worn Out Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Uneven Brake Lining Wear. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection Drum Brakes.
    • Glazed Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Incorrect Brake Lining Material. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Contaminated Brake Lining. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Brake lining Damage By Abuse. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Heat Spotted or Scored Rotors. Refer to Brake Rotor Tolerance
    • Brake Assembly Attachments Missing or Loose. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.

Brakes Chatter (Roughness)
    • Heat Spotted or Scored Rotors. Refer to Brake Rotor Tolerance
    • Improper thickness variation. Refer to Brake Rotor Thickness Variation Check in Disc Brakes, or Brake Drum Inside-Diameter Check.
    • Excessive lateral runout. Refer to Rotor Inspection.
    • Brake Assembly Attachments Missing or Loose. Refer to Brake Pad Inspection in Disc Brakes, or Brake Drum Inspection in Drum Brakes.
    • Loose Front Suspension Attachments. Refer to Fastener Tightening Specifications in Front Suspension.
    • Out-Of-Balance Wheel Assemblies. Refer to Tire and Wheel Balancing in Vibration Diagnosis.

Brakes Groan At End Of Stop

Brake lining Damage By Abuse. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.

Brake Warning Lamp ON
    • Leaking brake pipe, hose, or connection. Refer to Brake Fluid Leak
    • Leaking piston seal. Refer to Seal Leak Diagnosis
    • Leaking master cylinder (internal). Refer to Master Cylinder Diagnosis
    • Air in brake system. Refer to Hydraulic Brake System Bleeding
    • Contaminated or improper brake fluid. Refer to Brake Fluid and Brake Fluid Handling
    • Uneven Brake Lining Wear. Refer to Brake Pad Inspection in Disc Brakes, or Brake Shoe Inspection in Drum Brakes.
    • Park Brake Switch Circuit Grounded.
    • Parking Brake not Releasing. Refer to Park Brake Cable Service/Adjustment in Parking Brake.
    • Low Brake Fluid. Refer to Master Cylinder Reservoir Filling