Brake issues

1979 FORD BRONCO
87,000 MILES • 6.6L • V8 • 4WD • AUTOMATIC
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JOJO BROWN
  • MEMBER
  • 3 POSTS
Okay, this is a project vehicle. I replaced the master cylinder and brake booster 2 years ago. I have recently replaced brake hoses, calipers, wheel cylinders, and everything inside the back drums. I’m getting fluid to all of my calipers and wheel cylinders when bleeding. If the vehicle is off, I have good pressure, but once I start it up it goes almost to the floor and only has back brakes and nothing in the front. Please help me before I pull my hair out!
Feb 19, 2022 at 11:14 AM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,240 POSTS
Hi,

I have no hair left to pull out, so I'll try my best. LOL

I realize you replaced the master cylinder a couple of years ago, but it sounds like it is bad. When the engine is off, can you pump up the pedal and get a solid pedal?

Take a look through this link and let me know if it helps:

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

I have a feeling the primary plunger in the master cylinder which supplies pressure to the front brakes has failed. The little pedal you get is to the rear.

Let me know.

Joe
Feb 19, 2022 at 12:06 PM
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JOJO BROWN
  • MEMBER
  • 3 POSTS
Yes, it is a fairly solid pedal with the vehicle off.
Feb 19, 2022 at 12:15 PM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,240 POSTS
Okay, with the vehicle off, apply pressure to the brake pedal and see if it slowly goes down. I feel the master cylinder is the issue. The brake booster is making the issue easier to recognize.

Let me know.

Joe
Feb 19, 2022 at 1:16 PM
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JOJO BROWN
  • MEMBER
  • 3 POSTS
That was the issue thank you for your help!
Mar 1, 2022 at 12:54 AM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,240 POSTS
Hi,

You are very welcome. I'm glad to know you got it fixed.

Please feel free to come back anytime in the future if you have questions. You are always welcome here.

Take care,

Joe
Mar 1, 2022 at 10:57 AM
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