Brake pedal drops

Tiny
ABILENEGASDIESEL
  • MEMBER
  • 2015 FORD F-350
  • 6.7L
  • V8
  • TURBO
  • 4WD
  • AUTOMATIC
  • 166,500 MILES
We received this unit having trouble with vibration, found to need calipers and rotors which were replaced. While replacing tech left brake hoses draining so he did not plug the hoses, put all back together and brake pedal would go all the way down. Bled the system both with scanner and manually, took out all air. Then same problem had no brakes, therefore replaced master cylinder, bled once more both with scanner and manually and still same issue. When pushing pedal 2-3 times it stays up but after releasing and pushing once about a minute later the pedal drops all the way down. We sent to Ford dealership and seemed to not really be able to find issue, later stated that it could be the hydraulic booster however not too sure that could be issue, don't really believe could be that therefore trying to get more insight on this issue before going that route?
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Tuesday, August 25th, 2020 AT 5:09 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

It sounds like air in the system since you can get a pedal. But, it sounds like you did everything as far as bleeding. Do me a favor. Here are the directions from Alldata. See if there is anything that was missed. I noted you are a mechanic so I assume the bleeding procedures started at the right rear and worked to the closest wheel to the MC. I know that can make a difference on this system.

Just for curiosity, when it goes to the floor, do you have any functional braking? I assume this has a hydroboost set up. I wonder if that has something causing issues.
_______________________________________________

2015 Ford Truck F 350 4WD Super Duty V8-6.7L DSL Turbo
Brake System Bleeding
Brake System Bleeding
BRAKE SYSTEM BLEEDING
206-00 Brake System General Information 2015 F-250, 350, 450, 550 Super Duty
GENERAL PROCEDURES
Brake System Bleeding

General Equipment
Brake/Clutch System Pressure Bleeder/Filler
Fluid Container and Hose
Pressure

WARNING: Do not use any fluid other than clean brake fluid meeting manufacturer's specification. Additionally, do not use brake fluid that has been previously drained. Following these instructions will help prevent system contamination, brake component damage and the risk of serious personal injury.

WARNING: Carefully read cautionary information on product label. For emergency medical information seek medical advice. In the USA or Canada on Ford/Motorcraft products call the Poison Control Center at: 1-800-959-3673. For additional information, consult the product Material Safety Data Sheet (MSDS) if available. Failure to follow these instructions may result in serious personal injury.

WARNING: Do not allow the brake master cylinder to run dry during the bleeding operation. Master cylinder may be damaged if operated without fluid, resulting in degraded braking performance. Failure to follow this instruction may result in serious personal injury.

NOTICE: Do not spill brake fluid on painted or plastic surfaces or damage to the surface may occur. If brake fluid is spilled onto a painted or plastic surface, immediately wash the surface with water.

NOTE: Pressure bleeding the brake system is preferred to manual bleeding.

NOTE: The HCU bleeding procedure and a second brake system pressure bleed must be carried out if a new HCU has been installed.

All Vehicles

NOTE: Make sure the area around the master cylinder cap is clean and free of foreign material.

Pic 1

Fill the reservoir with clean, specified brake fluid. Refer to Specifications in this section.

Pic 2

NOTE: Master cylinder pressure bleeder adapter tools are available from various manufacturers of pressure bleeding equipment. Follow the instructions of the manufacturer when installing the adapter.

Install the bleeder adapter to the brake master cylinder reservoir and attach the bleeder tank hose to the fitting on the adapter.
NOTE: Make sure the bleeder tank contains enough specified brake fluid to complete the bleeding operation. Refer to Specifications in this section.

Open the valve on the bleeder tank.
Apply 207-345 kPa (30-50 psi) to the brake system.
With the vehicle in NEUTRAL, position it on a hoist. Section 100-02.
Bleeding steps must be followed in the order indicated in the graphic.

Pic 3

pic 4

pic 5

pic 6

Loosen the bleeder screw 180 and leave open until clear bubble free brake fluid flows and then tighten the bleeder screw.

Pic 7

Vehicles with rear integral parking brake calipers

NOTE: Due to the complexity of the fluid path within the rear integral parking brake calipers, it is necessary to press and release the parking brake during the bleed procedure.

Apply and release the parking brake 5 times. Loosen the rear bleeder screw. Leave open until clear, bubble-free brake fluid flows, then tighten the rear bleeder screw.
Repeat until clear, bubble-free fluid comes out.

Pic 8

All vehicles

Tighten the bleeder screw to specification. Refer to Specifications in this section.
Remove the fluid container and hose.

Pic 9

pic 10

Repeat steps 7-13 at the remaining wheel ends.
Close the bleeder tank valve and release the pressure. Remove the tank hose from the adapter and remove the adapter.
Fill the reservoir with clean, specified brake fluid. Refer to Specifications in this section.

Pic 11

pic 12

Vehicles with a new HCU installed.

NOTE: The HCU bleeding procedure and a second brake system pressure bleed must be carried out if a new HCU has been installed.

Using the diagnostic scan tool, follow the ABS Service Bleed instructions.
Repeat the brake system pressure bleeding steps.

___________________________________

Let me know.

Joe
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Wednesday, March 17th, 2021 AT 12:22 PM
Tiny
ABILENEGASDIESEL
  • MEMBER
Yes, brake system bleeding was done correctly therefore looks like it may be an issue then with the hydro-boost. We are going to replace that and hope that it fixes the issue as it looks to be all that is left that could be causing this issue. Thank you so much for all your help.
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Wednesday, March 17th, 2021 AT 12:22 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Happy to help. Do you need directions for the hydro-boost? Also, is it doing the same thing with the new master cylinder as it did with the old one? It's possible you have a bad MC even though it's new.

Let me know if I can help.

Joe
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Wednesday, March 17th, 2021 AT 12:22 PM

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