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Brake goes to the floor after replacing Master Cylinder

Tiny
JIM MATUSKA
  • MEMBER
  • 2010 MERCURY MILAN
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 80,000 MILES
I found the brake master cylinder reservoir empty, refilled and the brakes felt spongy. Took it to a dealer and they said I need a new master cylinder; I didn't let them repair it because of their price. ($940.00) Took it to another Ford dealer they had about half price to replace cylinder. ($500.00) Told them to do it. They called me, said after replacing the master cylinder pedal goes to the floor. Said I need two ABS modules replaced. ($1,700.00) I picked it up and paid them for what they did. ($572.00) Drove it home with parking brake. I can pump the pedal quickly and get a small amount of resistance but still the pedal goes to floor. No lights are on the dash, no check engine lights.
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Tuesday, December 14th, 2021 AT 3:50 PM

10 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,268 POSTS
If a module fails, you shouldn't have the brake go to the floor. That would be a serious hazard. Did you recheck the master cylinder reservoir level again? Also, did they happen to mention the module names?

To the best of my knowledge, there is one ABS module. See pic below.

Let me know.

Joe
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Tuesday, December 14th, 2021 AT 6:29 PM
Tiny
JIM MATUSKA
  • MEMBER
  • 6 POSTS
Thanks for the quick response. The said I needed ABS module and HCU.
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Wednesday, December 15th, 2021 AT 12:37 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

There is a safety recall on the HCU. Was it ever replaced or repaired under the recall? I know you mentioned it was at a dealership. Contact them and request they check if this falls under the recall. Note: The issue with the HCU is certain brake fluids cause the valves to stick open. See pics below. If the HCU is bad, the module will not function properly.

Go to this link for more information:

https://ford.oemdtc.com/4966/safety-recall-19s54-anti-lock-brake-system-hydraulic-control-unit-valve-function-2006-2010-ford-lincoln-mercury

Let me know if this helps or if you have other questions. Also, this recall was published in September of 2020, so it's not that old.

Take care,

Joe

See pics below. Note: I circled the recall number and highlighted the potential effects. You shouldn't have to pay for this repair.
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Wednesday, December 15th, 2021 AT 6:07 PM
Tiny
JIM MATUSKA
  • MEMBER
  • 6 POSTS
Today I took the lines off of master cylinder, screwed the adaptors on and plastic lines and pumped the master cylinder with brake pedal until I only had a few small bubbles, connected lines back up and pedal still goes to floor. I am thinking now that there is no fluid at all in the lines going to the wheels. What do you think?
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Thursday, December 16th, 2021 AT 2:20 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,268 POSTS
Hi,

It's possible. Did you check on the recall? Also, if you open one of the bleeders and allow it to sit, gravity should cause the fluid to eventually start coming out. Or there is a vacuum pump for the system that will draw the fluid through the system.

As far as the vacuum bleeder, most parts stores will lend you one.

Let me know what you find.

Joe
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Thursday, December 16th, 2021 AT 5:05 PM
Tiny
JIM MATUSKA
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  • 6 POSTS
No, I have not checked on the recall yet, I will when I get it running. I know we had the airbags replaced. I will get my son to help bleed them next week and I will see what I find. I will let you know. Thanks
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Thursday, December 16th, 2021 AT 6:36 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Sounds like a plan. Keep in mind, if valves in the HCU are stuck open, you won't get a solid pedal. I just don't want you to go crazy trying to get one.

Take care,

Joe
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Thursday, December 16th, 2021 AT 6:42 PM
Tiny
JIM MATUSKA
  • MEMBER
  • 6 POSTS
Okay, let me tell you what I have done and maybe someone can help me with this problem. I checked with Ford, and they do have a recall the HCU on my model and year car, but it doesn't include my SN.#. Since the last time I posted I have bled the brakes using the Phoenix reverse bleeder and was able to get good operating brakes, stops the car well, but they don't in gauge until an inch or two from the floorboard. After that I bled them the conventional way with two people and bleeding from the calipers. About the same results. Any help you guys can give me I would appreciate it.
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Thursday, December 30th, 2021 AT 6:11 PM
Tiny
JACOBANDNICKOLAS
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Hi,

I found the bleeding procedures right from my manual. I attached them below. I suspect you have already performed it this way but wanted you to see it.

Now, if you did it this way without change, then we need to check the HCU. If a valve is stuck open, it may be causing the issue.

By any chance, did you get the diagnostic trouble codes from the dealer that said it needed two modules replaced?

Let me know,

Joe

See pics below.
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Thursday, December 30th, 2021 AT 9:31 PM

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