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Brake pedal goes to the floor

Tiny
LORIED12
  • MEMBER
  • 2002 FORD F-150
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 180,000 MILES
Replaced front pads, rotors, calipers, ABS pump and master cylinder. I bled everything; brake pedal goes to the floor but when I pump the pedal the brakes work. Where should I look next?
Tuesday, April 19th, 2022 AT 5:55 PM

17 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Hi,

First, was this the issue prior to replacing the components? Also, I want you to do something. Turn the key off and pump the brake pedal to make it solid. Hold a steady amount of pressure on it and see if it slowly goes to the floor.

Also, I attached the bleed procedure from my manual. Take a look through it and let me know if there is anything you may have missed.

Let me know.

Joe

See pics below.
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Tuesday, April 19th, 2022 AT 8:46 PM
Tiny
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The original issue was brake pads. The brake pedal stays when you apply pressure with the key off.
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Wednesday, April 20th, 2022 AT 5:12 AM
Tiny
JACOBANDNICKOLAS
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Hi,

Okay, then it's unlikely there is a problem with the new MC. I suspect you still have air in the system. When you start the vehicle, you get the power assist which allows the pedal to reach the floor.

Did you bench bleed the new MC? Also, when bleeding, did you follow the directions listed above?

Let me know.

Joe
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Wednesday, April 20th, 2022 AT 7:15 PM
Tiny
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Yes, I followed the instructions on the bench bleeding the master cylinder. The only other thing I haven’t done is bleed the brakes while cycling the ABS pump. I also bled the brakes according to the instructions you posted twice before I asked any questions about what else could be wrong.
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Wednesday, April 20th, 2022 AT 8:08 PM
Tiny
JACOBANDNICKOLAS
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Hi,

I suspect that is where there is air in the system, the ABS.

I attached the directions for bleeding the ABS. It requires a scan tool that can communicate with the ABS module.

Take a look through them and let me know if it is something you can have done or get the scan tool to do yourself.

Take care,

Joe

See pics below.
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Wednesday, April 20th, 2022 AT 9:09 PM
Tiny
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My son has a scan tool we’re going to do it this weekend.
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Thursday, April 21st, 2022 AT 7:24 AM
Tiny
JACOBANDNICKOLAS
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Hi,

Excellent! Let me know if that takes care of the problem.

Take care,

Joe
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Thursday, April 21st, 2022 AT 4:04 PM
Tiny
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We bled the ABS pump and that didn’t change anything. At this point the only other thing is I’m wondering if I bought a master cylinder that is bad. After I replaced the Master Cylinder, I have a brake light on the dash that I didn’t have before. I’m going to return the one I installed and get another one to see if this is the issue.
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Sunday, April 24th, 2022 AT 6:35 AM
Tiny
JACOBANDNICKOLAS
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Hi,

If there are no leaks and everything is bled, the only other thing I can think of is if the pushrod between the MC and the booster is out of adjustment.

I attached directions for adjustment below. Check this before returning the Master Cylinder.

Let me know what you find.

Joe

See pic below.
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Sunday, April 24th, 2022 AT 6:37 PM
Tiny
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I checked the length of the push rod, and it is good. I then replaced the master cylinder. The brake light also went away. I also found the vacuum line to the power booster had a hole in it and replaced that. I need to bleed the brakes again, but the pedal still seems to go right to the floor when I first step on it. When I pump the pedal a few times it comes up and works close to normal. If bleeding the brakes doesn’t solve the issue, I’m not sure what to do next.
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Saturday, April 30th, 2022 AT 4:20 AM
Tiny
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Hi,

Thanks for the update. When you bleed it, make sure to also perform the automated bleed.
Also, and don't laugh, make sure the rubber brake hoses at the calipers aren't expanding when you apply the brakes. I've seen it happen twice in my life, but it can happen.

Let me know.

Joe

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Saturday, April 30th, 2022 AT 7:28 PM
Tiny
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I have now bled the brakes and there is no air to be found. The pedal still goes to the floor. All the lines look good. So, at this point is it possible the power booster is bad?
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Monday, May 2nd, 2022 AT 6:52 PM
Tiny
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Hi,

The brake booster simply makes pressing the brakes easier. Anything is possible, but that doesn't make sense to me. Hydraulics can only travel so far.

Are you able to pump the brakes up with the engine running or off, and get a good solid pedal?

Joe
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Tuesday, May 3rd, 2022 AT 3:38 PM
Tiny
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It’s still a little spongy I was talking with some who asked me if I was sure I had the calipers on the correct side after checking I think I switched them. I have the bleeders facing down and from the pictures they should be facing up.
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Tuesday, May 3rd, 2022 AT 3:54 PM
Tiny
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Hi,

Absolutely that is the problem. You can't get rid of the air if the bleeder is pointing downward. It sounds like you found the problem. I know it can happen but never thought to mention it because you had done so much work, I assumed they were correct. Well, that is what happens when one assumes.

Let me know if that takes care of the problem. I am very confident it will.

Take care,

Joe
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Tuesday, May 3rd, 2022 AT 5:29 PM
Tiny
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Yes, it took care of it. When I started this whole deal, I was trying to go too fast and fighting to get the parts before the stores closed. Thanks for the help.
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Tuesday, May 3rd, 2022 AT 8:13 PM
Tiny
JACOBANDNICKOLAS
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Hi,

I appreciate the update. Also, it's good to hear the problem is resolved.

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

Take care,

Joe
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Wednesday, May 4th, 2022 AT 2:35 PM

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