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Thread: Brakes locking on

  1. 03-05-2014, 06:26 AM #1
    michael70st
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    Brakes locking on

    I have had a problem with the brakes on my car sticking on. not just 1 but on all 4 at the same time without warning. Everything is going fine then I can feel the car dragging. The car then comes to a stop and the brakes are hard on. No amount of peddle pumping seams to do any good but if I open any of the bleed valves its all okay again instantly.

    I am assuming its something to do with the master cylinder but could do with some pointers before I pull it all apart. All of the callipers have been rebuilt and all the brake lines are new. I did rebuild the master with new seals. it went back together following the diagram in the manual so should be right and works fine 99.9% of the time with excellent pressure etc.

    This has only happened twice but its always when you could do without it and would be dangerous on a fast road.

    Any one had this before. Thanks

    PS: its a 1970 2.2 spec car all be it in ST trim
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  2. 03-05-2014, 06:40 AM #2
    Flieger
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    Did you make sure the brake pedal rod is not touching the master cylinder, but has a small amount of clearance?
    1971 911S, 2.7RS spec MFI engine, suspension mods, lightened
    Early 911S Registry Member #425
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  3. 03-05-2014, 07:43 AM #3
    M_deJong
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    Expanding on what Flieger said... anything that keeps the master cylinder piston from resetting to its proper rest position where the compensation hole is uncovered. Bad spring, debris in MC, bad pushrod adjustment...
    Mike de Jong | '71 911T/E 2.4 Tangerine | '74 911S 3.2 Ice Green
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  4. 03-05-2014, 12:39 PM #4
    michael70st
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    Thanks I will take a look at that. At the moment I have about 15mm of free play movement at the pedal before it makes contact. maybe this is too much. I re-bushed the assembly and the spring was replaced as part of the kit so it does sound like adjustment.
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  5. 03-05-2014, 04:04 PM #5
    beh911
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    Quote Originally Posted by M_deJong View Post
    bad pushrod adjustment...
    This.........
    1969 S Coupe #761
    Early S Registry #1624
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  6. 03-05-2014, 04:51 PM #6
    merbesfield
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    Did you check the lock nut on the adjust rod? I have had mine come lose causing the rod to come out of adjustment and lock the brakes on.
    Mark Erbesfield
    2018 911 Carrera T 7spd manual 😊
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  7. 03-05-2014, 10:59 PM #7
    michael70st
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    The lock nut was loose. and the rod had backed off giving all that free play. Thanks to you all for your help with this. Its saved me hours of work.
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