Noise when applying brakes then pedal goes to the floor

Tiny
KLUTHIN
  • MEMBER
  • 2003 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 145,000 MILES
Sometimes when applying my brakes it makes like a ssh. Sounds kind of like air in it and brakes go to floor, also have a hard time stopping. It does not do not all the time but more then not. My ABS light is on also as check engine light. Is it my master cylinder that needs replaced? Only car I have and I am kind of scared to drive it. Specially going down a hill it does not want to stop when applying the brakes so I just keep pumping them to try to get it to stop.
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Saturday, April 7th, 2018 AT 6:38 PM

2 Replies

Tiny
CARADIODOC
  • EXPERT
Intermittent loss of pedal does point to a bad master cylinder. If there was an external leak, you would have a low pedal all the time and you would be losing brake fluid. If the fluid level is going down in the reservoir, the best suspect is a leaking rear wheel cylinder. Sometimes they can seal after the brakes are released, and sometimes they can leak, depending on the orientation of the rubber lip seals when they retract.
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Saturday, April 7th, 2018 AT 7:01 PM
Tiny
ASEMASTER6371
  • EXPERT
Good evening.

The noise you hear is a vacuum leak from the power brake booster. It is leaking vacuum. That could be the cause of the hard stopping. It needs to be confirmed to be sure.

If it is, you will need to replace the booster.

As far as the ABS light, there is a malfunction in the electronic controls. A code is stored in the system. You can have this code read at a parts store for free. Once we know the code, it will give us a clue as to the area of failure. In most cases, it is a wheel speed sensor but needs to be confirmed.

Roy
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Saturday, April 7th, 2018 AT 7:13 PM

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