While driving randomly the brake pedal goes to the floor

Tiny
STEVE SANTAMARIA
  • MEMBER
  • 1999 CHEVROLET TAHOE
  • 0.5L
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
I’ve replace master cylinder brake booster, rear drums/shoes in addition to the front calipers/pads and hub assembly and bled the brakes by having my son pump and hold the brakes. I completely removed all air bubbles. My issue is the brake pedal randomly goes from normal to all the way down while driving. When I press it down and it feels normal the truck still rolls, In other words it doesn’t stop the way it should. Can the ABS be bad?
Monday, August 5th, 2019 AT 10:41 AM

1 Reply

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

You need a scan tool to bleed the ABS module. You cannot bleed it through normal bleeding procedures.

Roy

TWO PERSON PROCEDURE
1. Raise the vehicle in order to access the system bleed screws.
2. Bleed the system at the right rear wheel first.
3. Install a clear hose on the bleed screw.
4. Immerse the opposite end of the hose into a container partially filled with clean DOT 3 brake fluid.
5. Open the bleed screw 1/2 to one full turn.
6. Slowly depress the brake pedal. While the pedal is depressed to its full extent, tighten the bleed screw.
7. Release the brake pedal and wait 10 - 15 seconds for the master cylinder pistons to return to the home position.
8. Repeat the previous steps for the remaining wheels. The brake fluid which is present at each bleed screw should be clean and free of air.
9. This procedure may use more than a pint of fluid per wheel. Check the master cylinder fluid level every four to six strokes of the brake pedal in order to avoid running the system dry.
10. Press the brake pedal firmly and run the Scan Tool Automated Bleed procedure (below 15,000 GVW) once, or run the Function Test (above 15,000 GVW) four times. Release the brake pedal between each test.
11. Bleed all four wheels again using Steps 3 - 9. This will remove the remaining air from the brake system.
12. Evaluate the feel of the brake pedal before attempting to drive the vehicle.
13. Bleed the system as many times as necessary in order to obtain the appropriate feel of the pedal.
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Tuesday, March 16th, 2021 AT 10:09 AM

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