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Thread: Brake pedal staying put

  1. 06-17-2020, 06:51 AM #1
    damsroy
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    Brake pedal staying put

    Took the car yesterday for a spin and i could feel that something was not right. The car was stopping very fast when coming to a stop at a stop sign/light and not move even on a small incline.
    No wheel was hotter than the others so i ruled out one caliper being stuck or the handbrake being always on.
    After a quick investigation i realized that the brake pedal was staying put and that i had to pull the pedal by hand to release the brakes.

    What can cause the brake pedal to stay put? Where should i start my investigations?
    I replaced all the brakes and redid the calipers a few years ago. I didn't replaced the master cylinder.
    The car is not being driven enough but not sure this can cause the pedal to stay put.
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  2. 06-17-2020, 08:17 AM #2
    davep
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    The pedal cluster is seizing. That means a rebuild is required, and quite possibly a new master cylinder. The MC can leak into the pedal cluster and cause the seizing.
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  3. 06-17-2020, 08:54 AM #3
    NorthernThrux
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    If the brake pedal does not return to it's fully up position, it is keeping the MC pressurized. It is very typical even with a brand new MC that if you keep pressure on the brake pedal for a prolonged period that fluid will leak past the MC seal into the footwell. This creates more damage as the brake fluid is quite caustic.
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  4. 06-17-2020, 10:38 AM #4
    damsroy
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    Thank you both for chiming in. So bottom line i need to take he pedal cluster out and check it first?

    It is weird that it is happening right after i removed the brake/hand throttle assembly to replace the white plastic piece in the tunnel for the hand throttle but i don't see how both situations can be linked....
    Last edited by damsroy; 06-17-2020 at 04:39 PM.
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  5. 06-17-2020, 12:14 PM #5
    NorthernThrux
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    Coincidence, as the cables in the tunnel can't interact with the brake hydraulics. You don't have to take the cluster out to start. Just remove the wood pedal board and check for the full range of motion on the pedals. And the piston for the MC protrudes into that area, so you can easily see if fluid is leaking from that. Before you even do that, if you can easily look under the car, remove the metal tray that protects the MC and the steering rack and look at this hole on the firewall. If the MC is leaking from the piston seal, you will get brake fluid coming out of this hole eventually. That's how I knew my MC need to be replaced (that and the firmness of the pedal, despite 3 gravity bleeds, just sucked).

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    Early 911S Registry # 2395
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  6. 06-17-2020, 05:40 PM #6
    30westrob
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    The reason your brake pedal does not return is caused by swelling in the pedal bushings. When the plastic bushings come in contact with brake fluid they swell and bind. Your fix is to rebuild or replace the MC and replace all pedal bushings. Rob
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  7. 06-18-2020, 04:36 AM #7
    damsroy
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    Thank you. I will start putting together a list of all the bushings needed (unless such a list exist somewhere on this forum???)
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  8. 06-18-2020, 08:42 AM #8
    NorthernThrux
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    There was someone here offering full pedal assembly reconditioning for a reasonable price some time ago. I can't remember who, but they sure looked pretty. More than the cost of some bushings certainly, but depends of course on how far you want to go.
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  9. 06-18-2020, 11:20 AM #9
    RSTarga
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    Rebuild kits are available with the better bronze oilite bushings. Not a big job, but the rebuilt assemblies offered here are really nice, powdercoated pedals and all.
    David

    '73 S Targa #0830 2.7 MFI rebuilt to RS specs
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  10. 06-18-2020, 11:54 AM #10
    Arne
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    These are the bomb...

    https://www.early911sregistry.org/fo...=pedal+cluster
    - Arne
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