Annoying/intermentaly hum sound when slowly reversing and pressing the brake pedal on e46

[ItsMeScottG]

Does anyone know what would intermentaly cause a humming sound when slowly reversing an e46 and pressing the brake pedal? I know it's coming from the rear of the car, it only happens sometimes, and this is the last issue that I have to fix with this car. It's annoying and it's been happening off and on since I bought the car. I checked the rear brakes and they look good, any suggestions?

This video shows the exact sound I'm experiencing with my zhp.

http://m.youtube.com/watch?v=HwV2rZ5B4s0

[Simmsled]

Could have buildup in/on the rear brakes.
I get that sound after washing the car in the driveway, when a bit of rusty haze forms.

Have you considered a few quick stops from 40+ mph to clean off the rotors?

[ItsMeScottG]

It's been happening off-and-on since I got the car a year ago. I daily the car and i have put 17k miles on it since I bought it. I can't see that being the issue. Brakes look good

[Simmsled]

When you pull up your parking brake, how far does it go (or how many clicks) before engaging?

[ItsMeScottG]

I will test the Parking break in just a little bit and report back on here

[RITmusic2k]

I get that too, intermittently as you do. I've always chalked it up to brake dust but never considered that I never hear it when braking gently while moving forward. I can change brake pedal pressure to make it go away but it's still an occasional embarrassment.

If it's just a matter of adjusting the parking brake that'd be wonderful!

[ItsMeScottG]

Ok well I just tested my parking brake.

At 3-4 clicks, the parking brake doesn't hold at all.

At 5 clicks, the parking brake holds while in neutral.

At 7 clicks, the packing brake holds while in gear (reverse).

I am able to pull up the parking brake handle a total of 12 clicks.

Opinions?

[az3579]

It's not parking brake, it's your brake pads. I used to get that but ONLY with my Hawk HP+ brake pads. Whenever I swapped back to my street pads, the noise went away.

[ItsMeScottG]

Yeah I forgot to update this thread. I went ahead and adjusted my parking brake so it's perfect now. Also when I was adjusting my parting brake I noticed that my pads were actually getting thin, I just we tabard and installed new front and rear brakes including new rotors. I just went with factory Bmw pads and rotors. Car is now issue free

[billyjack]

Maybe not your issue but it can help clean some corrosion by pulling up the parking brake a little while you're coasting. Safer to do it while you're coming to a stop sign in a neighborhood for example. Push the button and hold it and gently pull the brake until you feel it grab. I do it every couple of months.

(I'm not responsible if anyone spins their car or gets rear-ended.... common sense rules apply )