Help me with Soft Brake Pedal after Upgrade

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

  1. 1950StangJump$

    1950StangJump$ forum member

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    2008 Mustang GT.

    So, installed new OEM style calipers/hawk pads/rotors on the back. New 14" rotors, hawk pads, and 4 piston (Brembo style) calipers on front.

    When I started by removing the old right/rear caliper, a bunch of fluid dripped out before it dawned on me to keep the master cylinder topped off. I topped it off, and it took about 1/3 quart, but I didn't think to look to see if MC had run dry. Besides, I didn't pump the brakes or do anything to suck air in. So, I went along with the install, topping off the MC occasionally going forward.

    Anyway, got everything installed, bled, and pads properly bedded per Hawk instructions. The brakes stop the car fine, but the pedal goes further down than I *THINK* it is supposed to before engaging. Once engaged, the car stops fine and the pedal never goes to the floor. But, it feels like it goes an inch or two before any engagement. In contrast, my 2017 Fiesta ST will jerk you forward when you press the pedal 1/2".

    I used a Motive bleeder and bled until nothing but nice clear, new fluid was coming out. I went in the right order for the 4 corners (RR, LR, RF, LF). But, I apparently did the wrong order on the 4-piston calipers, cause I bled the outside bleeder first. I don't think that would have mattered. All the pads appear to be lightly resting on the rotors as they should, and the handbrake works fine.

    Now, I'm starting to wonder if I'm going to have to pay someone to bleed out the ABS . . . and perhaps the master cylinder?
     
  2. stkjock

    stkjock ---- Madmin ---- Staff Member Administrator Super Moderator S197 Team Member

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    this is a common issue with these cars, there are several threads on the board about bleeding the system, IIRC the consistently best method was using a vac-pump on the Master Cyl to get the air out.

    IIRC - since the brakes/clutch work on the same system, have you noticed any issue with your clutch?
     
  3. 1950StangJump$

    1950StangJump$ forum member

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    No issues at all with the clutch.

    I loved how easy the Motive was . . . used the "dry" method by just pumping it to 12 lbs dry and pushing the fluid through when the bleeder was cracked open. Then, just released pressure after every corner and topped off the MC.

    I have used the vacuum method on other cars. My only beef with it is that you pull air around the bleeder. So, you see small bubbles when no air is actually in the caliper . . . so it becomes a guessing game about when the caliper is actually done.
     
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  4. 1950StangJump$

    1950StangJump$ forum member

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    I misunderstood. You're talking about using a vacuum pump on the top of the reservoir, then relieving the pressure quickly in order to "shock" the bubbles up to the top?
     
  5. stkjock

    stkjock ---- Madmin ---- Staff Member Administrator Super Moderator S197 Team Member

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  6. 1950StangJump$

    1950StangJump$ forum member

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    Thanks. I saw those when poking around. I guess I can try and bleed it a few more times, or I can take it to someone with the ability to bleed the ABS module and be sure it's done.

    I hate relying on someone else for a job I *thought* I knew how to do
     
  7. JeremyH

    JeremyH 3V Fuel Guru S197 Team Member

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    Since it does firm up and doesnt go all the way to the floor you have almost all the air out. Drive it for a week or so, pedal engagement will firm up as any remaining air makes it through the abs module and ends up in the calipers then a quick bleed again on all 4 corners and should be good to go.
     
    Villian likes this.
  8. Marble

    Marble forum member

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    I had the same problem and bleed the brakes twice and it still sucked. Turns out my caliper had twisted a few times, thus twisting the brake line. Just a thought.

    You have air in the line most likely...
     
  9. 86GT351

    86GT351 forum member

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    You can try to just gravity bleed all 4 wheels. With the Master Cylinder Cap off, open the bleeders individually in the correct order. If there is 1 Air Bubble in the system, it can easily aerate into more bubbles causing the softer pedal feel. I would let each wheel bleed for a few minutes. If that does not work then look into professionally bleeding including the ABS. If the system went low enough on fluid and pressure, air can get trapped in the module.
     
  10. 1950StangJump$

    1950StangJump$ forum member

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    Thanks, guys. I bled this morning again, and it is likely fine -- they feel pretty good now.

    Out of an abundance of caution, I am taking it tomorrow to get the ABS bled. I'm about 90% sure it won't change the feel I have now, but better safe than sorry.
     
  11. 86GT351

    86GT351 forum member

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    Good deal.
     
  12. PonyDNA

    PonyDNA Junior Member

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    OP,

    If the master was dry have the dealer bleed the master using the control module that activates the ABS. If they cannot bleed by ABS pump activation go where they have the controller that can do this.

    Additionally some brands of pads are naturally softer and have more compression, sometimes this changes after use slightly. I really noticed this when I rebuilt the brakes on my E36 M3 and switched to the then new EBC NXT pad material. The pedal was much stiffer under foot and faster to engage the rotors. Part of this may have been the replacement of the stock BMW caliper bushings with new stainless steel posts and bronze guides.

    But when I replaced the pads a few months later on my S197GT with the same EBC NXT compound for the 2-piece rotor big brake kit calipers I had the same high hard pedal with amazing feel for a street pad.

    Chip
     
  13. GriffX

    GriffX Member

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    Just a guess:
    If you install calipers with bigger volume and the master cylinder stays the same, shouldn't you press the pedal deeper than before to move a higher volume of fluid?
     
  14. 86GT351

    86GT351 forum member

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    Theoretically no. Larger volume but more fluid. Still can only compress a liquid so much with the spacing in the lines, etc. Good thought though
     
  15. 1950StangJump$

    1950StangJump$ forum member

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    Sad part is, I'm not even sure if the pedal that I feel is any different than it was before the brake upgrade. One of those things I didn't think to think about . . . until I did all the work and really started paying attention.

    I just know the pedal is not near as touchy/sensitive as my daily driver (a 17 Fiesta ST). That might be a function of 2008 vs. 2017 technology though.
     
  16. 01yellerCobra

    01yellerCobra forum member

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    FWIW, if you take the car somewhere that's slick and slam on the brakes a few times it'll do the same thing that the dealer is going to do. It's all about getting the ABS pump to activate. Last time I had to do that I took the car to a high school parking lot after it rained and slammed on the brakes a few times. The pedal felt better afterwards.
     
  17. 1950StangJump$

    1950StangJump$ forum member

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    I did that. Got the ABS activated easily enough. Like I said, I suspect the feel I have is what I can expect. But, will report back after the ABS is bled.

    Edit: If you're right, activating the ABS is just going to free up stuck air and send it to the calipers for later bleeding. That is the only way to logic through that. I think I'd rather just have someone activating it through the scanner and bleed it once and for all.
     
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  18. 1950StangJump$

    1950StangJump$ forum member

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    All good. So, the technician, who came highly recommended, came out to my car with the tool to bleed the ABS. I found him articulate and credible.

    But, he asked to take the car around the block, which I encouraged. He came back and said, "they feel great, there is no air in there." Since he just lost money, I have to assume he was being forthright.

    So, all's well that end's well. Might have been my last bleed that made the difference. I noted to the tech they still have a touch more travel than my aforementioned Fiesta ST . . . he responded that bigger calibers require more movement of the pedal because the pedal must push more fluid.

    I realize that idea is debatable (Post #14 above). I think if you need to "move" four pistons instead of two, it will naturally require more fluid movement. Whether the amount of additional movement is so minimal that you wouldn't notice it in the pedal travel . . . beats me.
     
  19. 01yellerCobra

    01yellerCobra forum member

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    I ended up doing something similar. Things never seemed right to me. I let a buddy take my car for a spin and didn't tell him about the caliper upgrade. After the first stop he asked what did I do to the brakes because they felt great.
     
    1950StangJump$ likes this.
  20. 1950StangJump$

    1950StangJump$ forum member

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    So often, I am paranoid or OCD about something I did to the car, and it's misplaced.

    But, I'm right just enough times to encourage such OCD the next time, LOL.