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  •  » Brake issues

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    2/24/2024 8:07 PM  #1

    Steve69
    Senior 24-7 FYI Addict

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    From: Madison Wisconsin
    Registered: 4/01/2013
    Posts: 2,615

    Brake issues

    He guys,

    Working on my son’s 68 mustang brakes.  The problem we’re having when you first hit the brakes with engine running the pedal goes 3/4 the way down.  Push the pedal again it’s where it should be.  The pedal is firm after bleeding with nice stream of fluid with no air bubbles.  It has Granda brakes on the front with explorer disk brakes on the rear.  We’ve bled them 4 times and no air bubbles.  The brake booster is new with 2001 Mustang V6 master cylinder.  We made sure the brake booster rod was adjusted properly to the master cylinder.  Maybe a bad brake booster?  With the engine not running and the car jacked up all the wheels locked the brakes with the pedal 1/4 pushed down.

    Thanks for the help.

     

    2/25/2024 1:34 AM  #2

    Ron68
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    From: Mukilteo, Washington
    Registered: 4/01/2013
    Posts: 1,399

    Re: Brake issues

    Did you bench bleed the master cylinder?

    68 coupe - 351W, 4R70W, 9" 3.25 -- 65 convertible - 289 4v, C4, 8" 3.00
     

    2/25/2024 9:19 AM  #3

    Steve69
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    From: Madison Wisconsin
    Registered: 4/01/2013
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    Re: Brake issues

    I don’t think we did.  But we do fluid coming to the calipers .

       •Thread Starter
     

    2/25/2024 9:36 AM  #4

    BobE
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    From: White Plains, NY
    Registered: 4/04/2013
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    Re: Brake issues

    The issue could be the volume of brake fluid being pushed to the calipers in the first stroke of the pedal requires more fluid to the caliper pistons to move the pads to the rotor, the second pedal stroke (before fluid can return to the master cylinder, and the piston/pads retrack) will adequately fill and engage the pads at a higher pedal travel.  Residual valves are the answer.
     

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    2/25/2024 10:21 AM  #5

    Nos681
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    From: Atlantic Mine, Michigan
    Registered: 7/14/2016
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    Re: Brake issues

    Might want to see if rear seal on brake master cylinder is leaking?

    May want to verify correct operation of the vacuum check valve on brake booster.

    Last edited by Nos681 (2/25/2024 10:24 AM)

     

    2/25/2024 12:27 PM  #6

    MS
    Forum Originator

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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 11,725

    Re: Brake issues

    Explorer rear discs have really large pistons.
    Also, be sure front calipers have bleeders pointing toward the rear of the car, not straight up.

    What booster and break pedal does it have?

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    2/26/2024 8:18 AM  #7

    John Ha
    I FYI 24-7

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    From: Mitchell, SD
    Registered: 4/02/2013
    Posts: 736

    Re: Brake issues

    MS wrote:

    What booster and break pedal does it have?

    "break" pedals are aka "push for a beer and a tinkle" pedals

    Founding Member of the Perpetually Bewildered Society
     

    2/26/2024 11:22 AM  #8

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 11,725

    Re: Brake issues

    John Ha wrote:

    MS wrote:

    What booster and break pedal does it have?

    "break" pedals are aka "push for a beer and a tinkle" pedals

    You have known me long enough to know that I know how BRAKE is spelled. I was shocked to see that incorrect word. I know I did not type break instead if brake. My SMART phone must have slipped it in when I wasn’t looking. I was going to quietly edit it to read BRAKE, but you had already made the mistake part of my permanent record, so I guess we just have to let this one go.

    I am typing this right now while I am taking a Pepsi break from working on my brakes.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    2/26/2024 3:28 PM  #9

    John Ha
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    From: Mitchell, SD
    Registered: 4/02/2013
    Posts: 736

    Re: Brake issues

    MS wrote:

    John Ha wrote:

    MS wrote:

    What booster and break pedal does it have?

    "break" pedals are aka "push for a beer and a tinkle" pedals

    You have known me long enough to know that I know how BRAKE is spelled. I was shocked to see that incorrect word. I know I did not type break instead if brake. My SMART phone must have slipped it in when I wasn’t looking. I was going to quietly edit it to read BRAKE, but you had already made the mistake part of my permanent record, so I guess we just have to let this one go.

    I am typing this right now while I am taking a Pepsi break from working on my brakes.

    You are correct.  I am sorry I did that (well, a little)   Please feel free to delete my post if you so desire.

    Last edited by John Ha (2/26/2024 3:28 PM)

    Founding Member of the Perpetually Bewildered Society
     

    2/26/2024 9:11 PM  #10

    Steve69
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    From: Madison Wisconsin
    Registered: 4/01/2013
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    Re: Brake issues

    MS wrote:

    Explorer rear discs have really large pistons.
    Also, be sure front calipers have bleeders pointing toward the rear of the car, not straight up.

    What booster and break pedal does it have?

    It’s a MS brake pedal and a EBay booster.  I believe the booster for the 68 mustang.

       •Thread Starter
     

    2/26/2024 9:56 PM  #11

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 11,725

    Re: Brake issues

    Aftermarket or a Bendix or a Midland?  There is a seal between the booster output shaft and the booster body. It should have silicone grease on it to seal the vacuum chamber.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    3/01/2024 12:24 PM  #12

    Steve69
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    From: Madison Wisconsin
    Registered: 4/01/2013
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    Re: Brake issues

    MS wrote:

    Aftermarket or a Bendix or a Midland? There is a seal between the booster output shaft and the booster body. It should have silicone grease on it to seal the vacuum chamber.

      Im pretty sure its the Bendix.  Ill check that seal.  Thanks
     

       •Thread Starter
     

    3/02/2024 9:18 AM  #13

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 11,725

    Re: Brake issues

    The symptoms do point towards a defective booster.
    Excessive travel tight before actuation. Assuming the output shaft is properly adjusted. This is not a definitive answer, though without actually seeing it

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    3/04/2024 7:23 PM  #14

    Steve69
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    From: Madison Wisconsin
    Registered: 4/01/2013
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    Re: Brake issues

    MS wrote:

    The symptoms do point towards a defective booster.
    Excessive travel tight before actuation. Assuming the output shaft is properly adjusted. This is not a definitive answer, though without actually seeing it

     
    Thanks!

       •Thread Starter
     

     

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