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Brake Issues...Cold morning confusion

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  • Brake Issues...Cold morning confusion

    I've been parking my car outside at night, and it's been getting cold lately.

    When I go to start the car in the morning, there is no movement in the brake pedal. My procedure is to park the car in gear. I get in, put my foot on the clutch and brake and start it up.

    The brake pedal is so stiff I can't push it down. The second I start turning the car over it feels normal. Why does it get so stiff sitting over night? When it's warm out I don't have that problem. Once the car is started the brakes feel absolutely normal, there is nothing wrong with them, function perfectly.

    Any ideas? Do I have some air in my line or something? It's always done this, I've just had a garage for the last 2 years so I forgot about it. Plus, in the summer when it's warm at night the car doesn't do this. Thanks for the advice

    '90 M3

  • #2
    I think the problem is with your brake booster loosing vacuum.

    I'd try replacing your non return valve first, because it's relatively cheap and easy to swap out. Follow the vacuum line coming off the brake booster, you'll see the non-return valve near the firewall. It's connected to the #4 throttle body.

    If that doesn't cure the problem you may have to replace your brake booster. It could have some dried out seals that work ok when warm but when they get cold they leak.


    • #3
      cool, thanks for the tip mick. I probably won't get to it until the car goes into storage because it's my only car at the moment. But thanks anyway, I appreciate the tip



      • #4
        What ^ he said.

        Disclaimer: Remember, I know absolutely nothing, but it doesn't prevent me from having an opinion or suggestion. :


        • #5
          Don't forget the vacuum hose that goes from the booster to the non-return valve.