Pedal goes to floor, brake light

Tiny
NNHALO360NN
  • MEMBER
  • 2003 CHEVROLET TAHOE
  • 4.8L
  • V8
  • 2WD
  • AUTOMATIC
  • 11 MILES
I am an 18 wheeler mechanic so my knowledge of hydraulic brakes is slim. Just changed front and rear brakes. When I changed the front left brake fluid overflowed from the reservoir when I compressed the caliper but only on that wheel. After replacing all the brakes I went to test drive but brake light was on and pedal goes to the floor. I tried engine off and pump the brakes hard then start engine but still did not help much at all. When I unplugged the sensor in the proportioning valve the light goes off. I read somewhere I need to reset the valve but unsure how. Main question, should I try and reset the valve or is my problem else where? Also I did not bleed the brakes.
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Saturday, March 30th, 2019 AT 3:51 PM

3 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good evening,

This sounds like the seals failed in the master cylinder. I would get a replacement master cylinder, bench bleed it and install. Then bleed all the wheels.

Roy
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Saturday, March 30th, 2019 AT 6:52 PM
Tiny
NNHALO360NN
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Would this be why so much fluid leaked back out when compressing the calipers?
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Saturday, March 30th, 2019 AT 7:07 PM
Tiny
ASEMASTER6371
  • EXPERT
When you pushed back the calipers, the fluid went back up into the master cylinder and forced its way out of the cap. That is normal.
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Saturday, March 30th, 2019 AT 7:34 PM

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