Brake pedal going to the floor

Tiny
KELVIN MORRIS
  • MEMBER
  • 2001 GMC YUKON
  • 5.3L
  • V8
  • TURBO
  • 308,051 MILES
I replaced the brake calipers and master cylinder and the pedal is still sinking to the floor. What is the problem?
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Tuesday, September 13th, 2016 AT 2:48 PM

7 Replies

Tiny
HMAC300
  • EXPERT
Probably the ABS unit, try a power bleeder first if that does not work a mechanic will have to open valves in ABS with his scanner.
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Tuesday, September 13th, 2016 AT 3:16 PM
Tiny
DDUNCAN70
  • MEMBER
Did you ever get this figured out.I have the same problem no leaks new master cylinder new calipers. Had a mechanic pull it in to his garage to check for leaks and bleed the system still no pedal. They worked fine until a brake line blew out and I replaced some line two calipers and master cylinder. Everything was bled and checked for leaks
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Thursday, February 22nd, 2018 AT 8:00 AM
Tiny
KEN
  • ADMIN
Hello,

You need to have a scanner connected the ABS system so you can open the ABS valves which will get the air out.

This video will show you how to connect the the ABS system.

https://youtu.be/rTtAnsOlZU4

This guide can help as well

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

Please let us know what you find.

Cheers, Ken

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Saturday, February 24th, 2018 AT 12:47 PM
Tiny
DDUNCAN70
  • MEMBER
I bought a scanner and did an abs auto bleed. Still no luck you can feel the abs push against you when the pedal goes to the floor. You can hear humming when you hold the brakes to the floor.I have someone looking at it soon.I agree maybe it s in the abs
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Monday, February 26th, 2018 AT 7:52 AM
Tiny
KEN
  • ADMIN
Sure sounds like it but to be sure lets use four vise grips and gently close off the rubber flex hoses. Once complete check the brake pedal it should be hard if there is a wheel issue and soft if it is the master or ABS.

Please report back

Cheers, Ken
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Monday, February 26th, 2018 AT 12:07 PM
Tiny
DDUNCAN70
  • MEMBER
I took my Yukon to a second mechanic. Found out the calipers were on opposite sides. The bleeder valves have to be on top.I had replaced the rear calipers and those were fine but the front ones were mixed up. Not sure how they bled them before but if the bleeders are not on the top they are on wrong they won t bleed correctly. Thanks for the replies. Brakes are great now
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Saturday, March 3rd, 2018 AT 11:01 PM
Tiny
KEN
  • ADMIN
Yep the calipers need to be on the correct side that's for sure quick pictures of the brakes and I could have lead us to the conclusion. Glad you got it fixed.

Use 2CarPros anytime, we are here to help. Please tell a friend.

Cheers, Ken
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Monday, March 5th, 2018 AT 10:33 AM

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