Help me with Soft Brake Pedal after Upgrade

Discussion in '2005+ Mustang GT 4.6L Tech' started by 1950StangJump$, Apr 1, 2019.

  1. MizterGT

    MizterGT Junior Member

    So I have to resurrect this thread. I recently installed the 2015 performance pack (brembo style) 4 piston front calipers. I am having the same issue.

    First, lots of travel and no engagement until the second pump. Messed with it, bled the lines multiple times, etc.
    Then I fixed an issue with a twisted line. Next day I went out and bled them once. Finally normal engagement, but on road test it just didn’t feel like it was stopping home it should. So I bled one more time thinking that would be good, annnddd no brake pressure.

    When you say the pedal goes to the floor do you mean literally the floor? Mine now goes way down and while the pedal is not resting on the floor, when i push in all the way I can feel it hitting something which I am assuming is “the floor”.

    Bled 3 more times and same thing. I have no idea why it would get pressure and then I bleed again and it’s gone???
  2. 1950StangJump$

    1950StangJump$ forum member

    Are you sure there are no leaks where the brake lines bolt to the caliper? I had that problem once.

    From there, I'd consider getting the ABS bled
  3. 08MustangDude

    08MustangDude Resident Fuktard

    Mine did the same thing till I bled them by the triple pump and hold
    method. I had brakes, but it was soft, and almost to the floor, unless
    I did a quick 2nd pump, then it was more firm. After I replaced ALL the
    brackets and calipers, bled the system, it's awesome.

    However, beforehand, the both rear brakes were 100% frozen; both the slide
    pins, and the caliper piston. Only one side was barely working, so those
    all the pads were new when I replaced the rears. I believe this was the main
    reason for the spongy pedal. Anyhow, as I said, I have ALL new hardware
    and it's fine.

    You may want to upgrade to stainless lines to the calipers as well. When the
    hoses get older, they will expand more with fluid pressure, that will also
    sponge up the brakes. Going to stainless braided lines will eliminate the
    hose swell, thus instant pressure to the pistons. The old rubber ones act
    like a buffer, and you don't want that.
  4. Juice

    Juice forum member

    Did you guys let all the brake fluid leak out swaping calipers?

    I never let that happen when doing any brake work, even just replacing the flex hoses. Service one wheel at a time, swap the part, and let it gravity bleed. Then move to the next/other wheel.

    If I want to change All the brake fluid, I syphon the master cyl and add fresh fluid before starting the work.
  5. ghunt81

    ghunt81 New parts on old junk! S197 Team Member

    Well one thing I wondered about with those 2015+ calipers was increased brake travel. The pistons in them are almost as big as the two in the factory calipers, but you have 4 now. So that is going to require more pedal travel to move them.
  6. Juice

    Juice forum member

    Possibly, but pedal feel should still be firm.
  7. 08MustangDude

    08MustangDude Resident Fuktard

    Not 100% true, but kind of... Once the calipers are full, it requires a tad more more
    volume to move 4 pistons -vs- two. However, the pedal travel should still be the same.
    IF what you said was true, then 4-piston braked cars equipped from the factory would
    need different pedal travel specs, and different master cylinder. If you can find that
    the S197 GT500 has a different pedal spec, and different master cylinder, then that can be
    partially true.
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