Sinking brake pedal

Tiny
WILLIAM MORRIS2
  • MEMBER
  • 2002 DODGE DURANGO
  • 4.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 200 MILES
Sinking brake pedal I replaced master cylinder and bled all brakes. I have vacuum on the check valve to the intake of I pull the valve out of the booster the pedal does not sink but as soon as I put the valve with vacuum back into the booster the pedal will sink. I pumped the brakes to empty vac and held my foot in the pedal and started car it does not indicate bad booster. Help I am stumped. Please.
Friday, December 30th, 2016 AT 11:19 AM

2 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
Forget the power booster. That has absolutely nothing to do with how far the brake pedal moves; only how easily it moves.

Do you have anti-lock brakes? If you do, there is a chance air got into the chambers in the hydraulic controller. You will need a scanner to command those valves to open so the air can be bled out.
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Friday, December 30th, 2016 AT 2:30 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Hey,

Also check the caliper slides becasue if they are sticking it will cause the caliper to back up slightly giving you a low pedal.

Here is a guide on how to service the slides.

https://www.2carpros.com/articles/how-to-replace-front-brake-pads-and-rotors-fwd

Please let us know happens so it will help others.

Best, Ken
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Saturday, December 31st, 2016 AT 2:31 PM

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