The brake pedal goes to the floor when running

Tiny
CALFMAN
  • MEMBER
  • 2005 BUICK LESABRE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 58,000 MILES
We needed new front rotors, and pads all around. It had a full pedal when the car was not running but pedal sank to floor while applying pressure when car was running. We then assumed an internal leak in master cylinder. We replaced the master cylinder with no improvement. We were told that it was the ABS computer module, we replaced that too, no improvement. What can cause this? We bled brakes three times, no air! Can it be a sensor or what? Asked a local GM mechanic, and he has not come across this one yet! Need help! Thanks, Calfman
Wednesday, November 10th, 2010 AT 3:13 PM

1 Reply

Tiny
SQM
  • MECHANIC
  • 6,383 POSTS
Hello,

You might have to bleed the brake system again. As this vehicle with ABS requires a special brake bleeding procedure with a scan tool to communicate with the ABS module.
Without the tool it will not bleed properly and will have braking issues.

Here is a helpful video on how to bleed ABS:

https://youtu.be/nQRnKyVyMuQ

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

I have attached the step-by-step instructions for the ABS bleeding below.

Please let me know if you have any questions.
Thank you.
Was this
answer
helpful?
Yes
No
Monday, January 31st, 2022 AT 1:19 PM

Please login or register to post a reply.

Sponsored links