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Thread: Brake "Feel" Question

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    Brake "Feel" Question

    Hello everyone!

    I searched through the forum for an answer to this but couldn't really find an answer to my inquiry...

    I've just made the change to the 500e from an i3 since I missed having a smaller car. My biggest disappointment with the car has been with the braking system. The brake pedal is very "heavy" relative to the i3's. My car is a 2014 with just 18K miles. I've requested the service history from the dealer that I purchased it from to see if they have been serviced. Meanwhile, do you mind sharing with me how your brakes "feel" under normal and hard braking? Additionally, I too feel the brake pedal buzzing when at a stop light waiting. I found a post earlier with this issue, but no resolution was posted. Please comment if you have had this issue, too!


    Cheers!

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    All I can advise is that my brake pedal feels "normal", like any other car I've owned. Of course the 500e doesn't have the high regen your i3 had.

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    The brake feel is "not light", but I wouldn't call it underboosted.

    The buzzing you're feeling is the assist charge pump. The brake booster works hydraulically. A pump charges up an accumulator with brake fluid, and that pressure is used to help "push" the pedal. ("Normal" cars use a vacuum booster, however some models use hydraulic boosters too. My 88 Audi and 03 Ford Powerstroke used the power steering system.)

    I'd recommend you change the brake fluid in the master cylinder reservoir. Because the accumulator is charged with brake fluid, the fluid level in the reservoir changes a bunch all the time. This draws air into the reservoir, which contaminates the fluid with moisture and turning it very dark. When we got our 2013 I had to change the fluid in the reservoir a couple times before it would stay clear. Just suck the old fluid out, and pour new fluid in (don't suck all the fluid out - leave a little in the bottom so you don't get air into the system).

    -J
    2013 500e
    2012 Passat TDI, 2004 Touareg V10 TDI, 1999.5 Jetta TDI, 1991 350SDL

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    It's definitely taking some adjustment for me. Occasionally the car comes to more abrupt stop than I like, but mostly I think it's a matter of adjusting to the car. (i frequently have similar trouble with rentals)

    i'll update if I feel like I can't reliably dial it in.

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    Thanks to everyone that replied.

    @CraigM - I haven't driven a "normal" car in a about three years but the rentals that I've had in this time had a much lighter feel to the brake pedal. Perhaps it will just take some time to adapt!

    @compu_85 - Thanks for sharing your experience and the insight as to how the 500's braking system is set up. I had a look at the reservoir earlier this week and it all looked well. I'll draw a bit of it to test the color. Did you flush your system with a vacuum system via the bleeder nipples? This is how I've typically gone about flushing brake systems in the past.

    @robus - I too have experienced this a few times. I'll say that it has gotten a little better over the four days that I have had the car. Perhaps it has sat for too long and there was some crud that accumulated on the braking system. Let us know how you feel after further adjustments!

    Thanks again to everyone!

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    Quote Originally Posted by compu_85 View Post
    The brake feel is "not light", but I wouldn't call it underboosted.

    The buzzing you're feeling is the assist charge pump. The brake booster works hydraulically. A pump charges up an accumulator with brake fluid, and that pressure is used to help "push" the pedal. ("Normal" cars use a vacuum booster, however some models use hydraulic boosters too. My 88 Audi and 03 Ford Powerstroke used the power steering system.)

    I'd recommend you change the brake fluid in the master cylinder reservoir. Because the accumulator is charged with brake fluid, the fluid level in the reservoir changes a bunch all the time. This draws air into the reservoir, which contaminates the fluid with moisture and turning it very dark. When we got our 2013 I had to change the fluid in the reservoir a couple times before it would stay clear. Just suck the old fluid out, and pour new fluid in (don't suck all the fluid out - leave a little in the bottom so you don't get air into the system).

    -J
    I ran to my car to check the brake fluid and can confirm that it's indeed a bit dark. It's likely that it's the original load. I'll have it changed and update you guys.

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    I drive a 2015 and have always felt the brake was heavy and grabby as well. There's nothing subtle about the feel of their braking system. I've become used to it but have never really like it.

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    I've noticed that if I get in the car and immediately start driving, the first couple of times the braking will be very sensitive and grabby. If I step on the brakes a couple of times before starting out (until I hear the buzzing of the brake pump), then the brakes feel normal. I think it is an issue of the hydraulics not always being primed.

  9. The Following User Says Thank You to rkw For This Useful Post:

    FFB500 (08-01-2017)

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    Quote Originally Posted by rkw View Post
    I've noticed that if I get in the car and immediately start driving, the first couple of times the braking will be very sensitive and grabby. If I step on the brakes a couple of times before starting out (until I hear the buzzing of the brake pump), then the brakes feel normal. I think it is an issue of the hydraulics not always being primed.
    Doesn't that sound like Air in the brake lines?

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    Quote Originally Posted by forby View Post
    Doesn't that sound like Air in the brake lines?
    Air in the brake line makes the brakes feel soft, spongy and unresponsive. In my case, the brakes are grabbing suddenly while braking with light pressure.

    In a gas engine car, the running engine is used to keep the brake hydraulics continually pressurized. In the 500e, the pressure is provided by an electric pump that runs periodically (the brief buzz or whirr you can hear) and I think this may the cause of uneven behavior.

  12. The Following User Says Thank You to rkw For This Useful Post:

    FFB500 (08-01-2017)

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