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Thread: Donor front brake caliper question

  1. #1
    Senior Member Cobradavid's Avatar
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    Question Donor front brake caliper question

    My passenger-side front brake caliper isn't releasing fully and it drags on the rotor a little. It doesn't drag enough to make the roadster pull to that side, but there is slight resistance to rolling.
    Also, after diving the car a dozen miles or so, that wheel is hotter than the driver-side wheel.

    I've removed the caliper and cleaned and lubed the mounting pins and surfaces but the problem hasn't gone away.

    Build specifics:
    2001 Mustang GT hydraboost master cylinder and hydraboost unit
    2001 Mustang GT brakes (the PBR calipers). Donor had ~46k miles.
    New pads installed when I built the roadster. The roadster has 13k miles and there have been no issues with the brakes prior to this.

    Any thoughts on what could cause this dragging?

    David
    My Saving Grace: John 3:16

    FFR6687, Graduate #39 in the Class of 2009
    The Factory Five Forum March 2012 POM

  2. #2
    Gordon Levy's Avatar
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    Check the pushrod on the pedal and make sure you have some freeplay
    Go Fast Part and tech Specialist [email protected]
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  3. #3
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    Gordon, could you expand on that a little?

  4. #4
    Gordon Levy's Avatar
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    OK, when you hook up the brake pedal to the push rod, some use and adjustable push rod. Somethings the jam nut comes loose and the rod starts putting pressure on the master and the brakes start dragging. An easy way to tell is that the brake pedal has no freeplay. You need to have a little or this issue can arise
    Go Fast Part and tech Specialist [email protected]
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  5. #5
    Senior Member Cobradavid's Avatar
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    Thanks for the assistance, Gordon.

    The brake pedal has a little free play. Also, I don't see any jam nut between the pedal and the push rod. I used the stock pedals and pedal box from the 2001 GT. Is an adjustable push rod an after-market part or was that stock?

    Only the passenger side front brake is dragging, the driver side turns freely and that wheel doesn't get warm after driving like the passenger side does. Would the push rod jam nut affect just one side?

    When checking the pedal play and looking for a jam nut, I noticed a drop of ATF/power steering fluid on the brake pedal push rod, so I guess the hydraboost unit has a slight leak. Could that cause one corner to drag?

    Is there a caliper rebuild/replace task in my future?

    David
    My Saving Grace: John 3:16

    FFR6687, Graduate #39 in the Class of 2009
    The Factory Five Forum March 2012 POM

  6. #6


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    Jeff Kleiner's Avatar
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    Quote Originally Posted by Cobradavid View Post

    Is there a caliper rebuild/replace task in my future?
    I think so. The composite pistons in the PBR calipers have a reputation for sticking.

    Jeff

  7. #7
    Senior Member Cobradavid's Avatar
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    Thanks, Gordon and Jeff for sharing your expertise!

    Will a caliper re-build fix this or should I just bite the bullet and replace the front calipers. I'm a government employee and I'm not getting paid right now with the government shut-down, so I need to watch the expenses!

    David
    My Saving Grace: John 3:16

    FFR6687, Graduate #39 in the Class of 2009
    The Factory Five Forum March 2012 POM

  8. #8
    Gordon Levy's Avatar
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    You can replace 1 but I always do them in prs. You should be able to get rebuilts from your local parts house pretty cost effectively.
    Go Fast Part and tech Specialist [email protected]
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  9. #9
    Member FlyingCobra's Avatar
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    I'd replace the caliper with a rebuilt one. Rebuilt front calipers are pretty inexpensive, and I would replace it. I've had this issue on Fords over the years. If you check your local parts house or Rock Auto, you can find one pretty cheap. I usually buy mine locally from Advance or O'Reilly.

    It generally is considered better to replace the calipers in pairs to keep things even. That said, I have replaced single calipers on several occasions when they've stuck and I've never observed adverse effects from it. So if you're tight on funds now, I'd just replace the single caliper and that will probably work just fine for you.

  10. #10
    Senior Member Cobradavid's Avatar
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    Thanks, guys! A pair of replacement calipers is the plan now.

    David
    My Saving Grace: John 3:16

    FFR6687, Graduate #39 in the Class of 2009
    The Factory Five Forum March 2012 POM

  11. #11
    Senior Member AC Bill's Avatar
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    Check Amazon as well, Sometime you can get excellent prices and free shipping.

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  13. #12
    Senior Member CraigS's Avatar
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    Just replace the one that is sticking. I know a lot would say do both and that's fine if one wants to be preemptive. You could replace the rotors and pads too. You could replace the rears too. But if your budget is tight, fix what is wrong and move on.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

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