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An inexplicable grinding noise coming from the brakes


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Six-speed touring 2016 Mazda6
Two technicians are perplexed by a mysterious braking noise. After having the brakes and rotors serviced, something occurred. Have had them recut with no success. There is zero wheel trembling or dragging. Several times, in order to examine the brakes, they were taken apart. The pins were adjusted by the mechanic, but nothing happened.
Reverse braking does not result in this.

The last moments of braking, when you come to a complete stop, are accompanied by a very pronounced and loud noise.







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The video's quality isn't great, but the problem doesn't seem to be a broken axle. This is just conjectural, however I have heard a similar noise in a customer's car and one of my own. There is no noise produced by the front suspension while the car is on the rack and the weight is not pressing down on it. Finally, with the use of a sound meter, I was able to pin the increased noise level during mild braking on the output shaft seal. Since the axles often had a lot of miles on them, I went ahead and swapped out the whole assembly, bearings if necessary, and output shaft seal. There is no longer any noise.

The argument is that the suspension was hanging in an abnormal position, speeding up the wear on the axle or seal, and the noise only started when the brakes were used.

All I have to go on is hearing what I assume was a familiar sound and seeing the incredibly brief and low-quality recordings.

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Videos make it hard to hear, but when the vehicle is going faster than roughly 15 mph, you can hear a squeaking sound that is reminiscent of the low brake pad warning when you use the brakes. The other sound, which I'll grant sounds like a suspension sound, is only audible at extremely low speeds, but disappears as soon as you release the brake.

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However, I must admit that the noise began after I had a local mechanic work on the brakes. They went back three times, at which point they attempted recutting and replacing the pins because they thought there could be some wiggle room.
Mazda checked them out since I was taking the car in to get the tensioner replaced under warranty. After I inquired about the noise, they decided to have the struts replaced.
The report concluded, "Well, we do see some hot spots on the rotors."

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Okay, reread my first response: plenty of noises may result from applying force. The fact that the sound disappeared when the brakes were adjusted is proof here. The noise is probably not coming from the brakes, but rather the axles. Just have another "qualified" individual listen to it without knowing anything about the recent brake work. This manner, they won't automatically assume that the problem is due to the brakes. This is why I recommend having it checked out at Firestone. Instead of being baffled by the brakes, the mechanic will observe the newer components and check elsewhere for the source of the noise. I'll have one of my Technicians analyze the situation and give some attention to their diagnosis if I have a client who appears to know more than me (LOL) and if there is a condition that I now have stuck in my head from that "smart" customer as to what it was.

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