Brake pedal goes to the floor?

Tiny
JB3
  • MEMBER
  • 1997 FORD F-150
  • 4.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 180,000 MILES
I have changed all brake parts, new calipers, new wheel cylinders, new pads, new master cylinder and booster and the cylinder rod adjusted. The problem is when I depress the brake pedal it goes normal until close to the bottom and then continues about a quarter inch with a clunk at the bottom. This issue did not appear until the brake service was done. I have had three different mechanics look into this with no resolve. Any help would be greatly appreciated.

Thank you in advance.
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Friday, November 24th, 2017 AT 6:05 AM

64 Replies

Tiny
PATENTED_REPAIR_PRO
  • EXPERT
It sounds like they did not bench bleed the master here are two guides that will help us fix the problem

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

and

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

Please run down these guides and report back.
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Friday, November 24th, 2017 AT 7:23 AM
Tiny
JB3
  • MEMBER
The noise appears to be in the pedal but did not exist until the brake job was done. I will check these things as you suggest but find it hard to understand how this is now all of a sudden happening after a complete brake job.

Thank you for your assistance.
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Friday, November 24th, 2017 AT 7:28 AM
Tiny
KEN
  • ADMIN
If there is no air in the brake system then the only two other things that can cause this problem is a defective master or the rear shoes are out of adjustment. Here are a couple of guides to help you get the problem fixed.

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

and

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

and

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

The clunk you feel is normal when the master cylinder bottoms out.

Please let us know what happens.

Cheers, Ken
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Sunday, November 26th, 2017 AT 7:09 PM
Tiny
GLEN WORSTALL
  • MEMBER
I have a 98 Ford f150 4-wheel drive with a 4.6 Triton that we put new calipers new brakes new bleeders new banjo bolts and everything in it tried bleeding it with no success
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Friday, August 23rd, 2019 AT 7:58 PM
Tiny
GLEN WORSTALL
  • MEMBER
I need to figure out what's wrong with this truck.
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Friday, August 23rd, 2019 AT 8:00 PM
Tiny
KEN
  • ADMIN
Hello,

Does this truck have ABS? if so you will need to have the the ABS unit valves opened when bleeding using a scan tool.

This guide should help us:

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

Please run down this guide and report back.
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Monday, August 26th, 2019 AT 11:54 AM
Tiny
SSTANELLE
  • MEMBER
Could air trapped in the ABS unit be causing the sinking brake pedal? It's my understanding that if the master cylinder is replaced, the ABS unit must be bled in conjunction with wheel-based bleeding. Can an expert confirm or deny this? I took into my local mechanic for a spongy brake pedal. He assumed it was the master cylinder. But after bleeding the brakes, the problem still exists. He then replaced the brake booster and bled the brake system again. Still the spongy brake pedal problem exists. He also replaced the front brake pads and rotors because it was needed to be done anyway after a complete inspection of the brake system. I didn't ask him yet if he bled the ABS unit because I don't know if that is a legitimate concern or not. Hopefully someone here can answer. I also don't know if he is equipped to do so as I believe it requires a scan tool to open the valve for each wheel independently. Also, can an expert tell me how far the brake pedal should normally travel? Thanks!
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Wednesday, August 28th, 2019 AT 9:37 AM
Tiny
KEN
  • ADMIN
The brake pedal should travel about 3 inches, you will need a scan tool to open the ABS control valves to get he air out, here is a guide that should help.

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

Please run down this guide and report back.
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Thursday, August 29th, 2019 AT 10:40 AM
Tiny
NOEL RIVOTA
  • MEMBER
  • 1997 FORD F-150
Brakes problem
1997 Ford F150 Four Wheel Drive Automatic

When we turn the wheel to the left the brake pedal sinks all the way to the floor as if it has no brakes, when we turn to the right it does not do that.
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Monday, January 6th, 2020 AT 11:58 AM (Merged)
Tiny
MASTERTECHTIM
  • MEMBER
Check the front wheel bearings. If a bearing is loose it will rock in and cause the caliper to compress and then you will need to pump pedal to get it to come back out
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Monday, January 6th, 2020 AT 11:58 AM (Merged)
Tiny
UNPLUGGED_IN_MN
  • MEMBER
  • 1997 FORD F-150
  • 6 CYL
  • 4WD
  • MANUAL
  • 170,000 MILES
I changed the right front caliper on my 97 F-150. Every thing was working correctly prior to the change, besides the caliper hanging up. I installed the new caliper and it bled fine. However, after a min of sitting the peddle goes to the floor. You can pump them up in the pumps but then start the ignition and the peddle goes to the floor again. Any thoughts?
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Monday, January 6th, 2020 AT 11:58 AM (Merged)
Tiny
CARADIODOC
  • EXPERT
Hi unplugged_in_mn. Welcome to the forum. What does "You can pump them up in the pumps" mean? Let's hope there is still air trapped in the line. A quick fix, now that the caliper is pumped up and applied is to use a flat blade screwdriver to pry the piston back into the caliper to push the fluid back up to the reservoir. That will wash any air up there too.

A fairly common problem is caused by pedal-bleeding if the pedal is pressed all the way to the floor. Corrosion and debris build up in the bottom halves of the bores in the master cylinder where the lip seals don't normally travel. By pushing the pedal to the floor, the lip seals get torn on that debris. I always instructed my students to pretend there was a block of wood under the pedal and to never push it more than half way to the floor. Still, every year I had someone wreck a master cylinder. Typically you will notice the pedal sinking slowly to the floor when you hold steady pressure on it if the seals are ripped. In most cases a rebuilt master cylinder actually costs less than the rebuild kit that lets you do it yourself.

Caradiodoc
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Monday, January 6th, 2020 AT 11:58 AM (Merged)
Tiny
PHIL RAINS
  • MEMBER
  • 1997 FORD F-150
  • 4.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 136,000 MILES
I have installed new calipers, pads, front brake lines, master cylinder, rear wheel cylinders, bled all the air from the system and have to pump the brake peddle several times to have any peddle with the engine off. As soon as I start the engine the peddle goes straight to the floor. I do not understand it, the brakes were fine before I installed the new calipers. Any suggestions?
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Monday, January 6th, 2020 AT 11:58 AM (Merged)
Tiny
ED-WEEZY21
  • EXPERT
It sounds like you may either still have air trapped in the brake system or you might have a bad brake booster. You replaced a lot of components so that is a lot of time for air to get into the system. If manually bleeding it does not work, try gravity bleeding the system. Just crack all the bleeder screws loose and let it be for about thirty minutes while making sure the reservoir does not run dry. Also make sure not to depress the brake pedal. As for the brake booster, make sure there are no leaks where the brake pedal rod goes into or where the master cylinder bolts into. Also make sure all applicable vacuum lines are attached.
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Monday, January 6th, 2020 AT 11:58 AM (Merged)
Tiny
PHIL RAINS
  • MEMBER
Gravity bleeding did not help at all.
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Monday, January 6th, 2020 AT 11:58 AM (Merged)
Tiny
PHIL RAINS
  • MEMBER
I am going to take it to a brake shop.
But thank you just the same.
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Monday, January 6th, 2020 AT 11:58 AM (Merged)
Tiny
CHAD READ
  • MEMBER
  • 1997 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 1,000 MILES
I replaced the master cylinder, replaced brake booster, new brake pads, turned rotors, replaced calipers. Tried bleeding brakes in sequence over and over, bench bled master cylinder. Front brakes squeeze together and won't let go. And pedal still sinks to the floor.
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Thursday, September 24th, 2020 AT 11:46 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
HI and thanks for using 2CarPros.

It sounds like an issue with one of the rubber brake hoses to the caliper. I need you to try this for me and let me know what happens.

First, safely lift the front wheels off the ground so you can turn them. Apply the brakes so the caliper locks. Open the bleeder on the brake caliper. Does the caliper release?

If so, do this. Apply the brakes to lock caliper. Release pressure at the master cylinder. If it doesn't release the caliper, replace the rubber brake hoses.

Here are the directions specific to your vehicle for brake hose replacement. The attached pictures correlate with these directions

Front brake hose
Removal:
Warning: brake fluid contains polyglycol ethers and polyglycols. Avoid contact with eyes. Wash hands thoroughly after handling. If brake fluid contacts eyes, flush eyes with running water for 15 minutes. Get medical attention if irritation persists. If taken internally, drink water and induce vomiting. Get medical attention immediately.

- Raise and support the vehicle.

Warning: the electrical power to the air suspension system must be shut off prior to hoisting, jacking or towing an air suspension vehicle, this can be accomplished by turning off the air suspension switch located in the right hand kick panel area. Failure to do so may result in unexpected inflation ()r deflation of the air springs which may result in shifting of the vehicle during these operations.
Disconnect Front Brake Hose
see picture 1

- Disconnect the front brake hose.
1 Remove the front brake hose bolt.
2 Remove and discard the copper washers. Plug the front brake hose.
3 Disconnect the front brake hose.

Remove Front Brake Hose
see picture 2

- Remove the front brake hose.
1 Disconnect the front brake tube fitting and plug the tube.
2 Remove the plug;
3 Remove the two brake hose frame bolts.
4 Remove the front brake hose.

INSTALLATION:

Front Brake Hose Torque Specifications
see picture 3
Front Brake Hose Torque Specifications
see picture 4

- To install, reverse the removal procedure.
Bleed the front brakes; refer to procedure in this section section.
Let me know what you find.

________________________________________________

Also, since both the booster and master cylinder were replaced, you really should check the push rod adjustment between the two. Here are the directions for adjustment, Pic 5 correlates with this process.

Remove the brake master cylinder: refer to the Master Cylinder, Brakes.

Power Brake Booster To Master Cylinder Push Rod Torque Specification

see picture 5

-Adjust the power brake booster to brake master cylinder push rod.
1 Measure the power brake booster to brake master cylinder push rod.
2 If necessary, adjust the screw to the proper length.

Let me know what you find or if you have other questions.

Take care,
Joe
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Thursday, September 24th, 2020 AT 11:46 AM (Merged)
Tiny
CHAD READ
  • MEMBER
I forgot to mention I also replaced the brake hoses.
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Thursday, September 24th, 2020 AT 11:46 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Okay. Did you adjust the push rod? It sounds like something isn't put together correctly there. If nothing leaks, everything is new, either the master cylinder is bad or the push-rod is not properly adjusted and getting stuck causing the pressure to remain on the calipers. Try the release procedure I suggested. At least that way we will know if the problem is at the master cylinder or after it. THis guide can help us

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

Please run down this guide and report back.
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Thursday, September 24th, 2020 AT 11:46 AM (Merged)

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