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

Step

Action

Normal Result(s)

Abnormal Result(s)*

1

Check the master cylinder fluid level.

Master cylinder fluid level between ADD and FULL.

Master Cylinder Reservior Filling.

2

Check the power steering fluid level.

Power steering fluid level between ADD and FULL.

Fluid Level Adjustment in Power Steering System.

3

Perform Hydraulic Booster Fuctional Test. Refer to Hydraulic Booster Functional Test .

Brake pedal falls away and then pushes back.

Accumulator Leak-Down System Not Holding Charge.

4
  1. Turn ignition OFF.
  2. Park brake not applied.
  3. Start the engine.

Brake warning indicator illuminates briefly (approximately 5 seconds).
    • Brake Warning Indicator Always ON.
    • Brake Warning Indicator Inoperative.

5

With the vehicle in PARK, perform the Brake Pedal Travel Test. Refer to Brake Pedal Travel .
    • Brake pedal moves steadily towards floor, approximately 2-3 in.
    • Brake pedal stops and is firm against the pressure (Hydraulic brake booster may hiss or clunk/click/clatter with high brake pedal effort).
    • Brake Pedal Excessive Travel.
    • Brake Pedal Travel Gradually Increases.
    • Brake Pedal Excessive Effort.
    • Hydraulic Brake Booster Noisy.

6

Depress the brake pedal.

Brake pedal returns to normal height.

Brake Pedal Slow Return.

7
  1. Press the brake pedal.
  2. Shift vehicle into DRIVE.
  3. Perform the Brake System Test. Refer to Brake System Testing .
    • Braking action starts after applying the brakes.
    • Brakes do not grab - brake pedal does not vibrate.
    • Vehicle stops without excessive pedal effort.
    • Vehicle stops without pulling to one side.
    • Front and rear brakes apply evenly.
    • Vehicle stops without noise coming from the brakes.
    • Vehicle stops without noise coming from the hydraulic booster.
    • Brakes do not drag after releasing the brake pedal.
    • Brakes do not make noise while driving.
    • Brake System Slow Response.
    • Brake Pedal Excessive Effort.
    • Braking Uneven - Side to Side.
    • Braking Uneven - Front to Rear.
    • Brake System Noise with Brakes Applied.
    • Brake System Groan at End of Stop.
    • Hydraulic Brake Booster Noisy.
    • Brakes Drag.
    • Brakes System Noise with Brakes Not Applied.

8

While driving the vehicle, turn the steering wheel without pressing the brake pedal.

Brakes do not apply while turning the steering wheel.

Brakes Self-Apply When Turning Steering Wheel.

* Refer to the appropriate symptom diagnostic table for the applicable abnormal result.