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Shifting Noise


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I can hear a shifting sound from my brakes each time i turn on the car. I can sorta feel it on my foot when my foot is on the brake. But even without my foot on the brake, I can hear the noise. Its only for about 4-6 seconds than goes away but continues to make the sound every now and then when i get to a traffic light or while driving at a slow speed than coming to a stop. I hear the noise when my car is idle or while going 10-30 mph, not when im driving at fast speeds. Lexus dealer told me its my ABS brakes shifting and the sound lets me know that its "doing its job". I just dont believe lexus engineers would want to get on someones nerves like that. Anyone have this problem or know what im talking about? please help. thx

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The sound is the hydraulic booster pump maintaining system pressure. As brake system pressure is not vacuum assisted in this car, this is by design.

After a few applications of the brakes, the system pressure reserve drops and the pump kicks in. The pumps runs until the pressure builds up and turns off. It is rather annoying, I do agree. You can verify this by starting the car. Listen for the pump to turn off. Press the brake fully a few times until you hear the sound again. It should run for a few seconds and stop. You can repeat this as many times as you like.

The worst part of this design is when descending a hill. After you touch the brakes a few times, the pump will sometimes kick in just as you apply the brakes causing the car to jerk forward a bit. I simply was besides myself when I realized this was how the system was designed. While this may or may not be as noticeable in some cars or to some drivers, I have felt it in every GS I have driven.

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Thank you! I also felt that slight jerk while driving and said "what the hell?". "is this normal?". Oh well, at least now I know its not a problem and thats just the way the car was built. Thanks again for the detailed explanation.

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