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-   -   did brake job/rear shock mount, have strange noise now (http://www.bimmerfest.com/forums/showthread.php?t=672409)

natman589 01-25-2013 08:27 PM

did brake job/rear shock mount, have strange noise now
 
last weekend i replaced the rear brakes/rotors and shock mounts, as they were both due to be done.

while working on the left side of the car, it was nice enough to slip the stand and fall. it fell into the wheel that had been removed, so the rotor fell into the bottom of the rear left wheel, if that makes sense. it did not hit the ground.

in any case, now the car makes a low-pitched, pulsating sound when moving forward at very low speeds (i.e. idle speeds) or when turning left. as the car speeds up, the pulsating noise is more frequent.

the guy i was working on the car with suggested i look at the 'splash guard' behind the rotor to see if it had been bent and pressing up against the rotor. i looked and it had been flattened, so i bent it back into shape away from the rotor, however the noise continues.

ive entertained the idea that it may be a bad wheel bearing, but would be interested to see if anyone thinks it could be something else. braking power seems to be normal, and the noise is there regardless of application of the brakes.

any ideas would be appreciated

natman589 01-25-2013 08:36 PM

also, since the job, my parking brake has suddenly become much harder to engage - i need to pull the lever all the way up, waaaay past where id normally have to, just to have any kind of braking power through the parking brake

jvr826 01-25-2013 08:43 PM

Did you bed in the parking brake shoes on the new rotors? If not, that is why the parking brake isn't working. You do this at low speeds in a safe area, parking lot. Drive along, press in the release button on the parking brake lever, and engage the brake. You'll do this several times until it starts to grab well. What you're doing is depositing some pad on the inside of the rotor hat.

I wouldn't freak out on the noise just yet. Go thru the procedure a few times and see if it goes away. If not, lift the corner of the car and spin the wheel manually to see if you can pinpoint it better.

jhurless 01-25-2013 10:33 PM

I'll bet the backing plate is just barely contacting a spot on the rotor. The clearances are very tight.

As stated by jvr826 your best bet is to lift up the car and spin the wheel.

natman589 01-26-2013 10:01 AM

the squeal is still there, just not as bad as before i took pliers to it, so im going to go at it again and see what i can do.

Also, i had never heard of needing to bed in your parking brake, although it makes sense. i gave it a go 5-6 times, and it doesnt seem to have improved any. since the parking brake does actually hold the car on my driveway, would it be acceptable to simply adjust the parking brake to a tighter level?

SJBimmer 01-26-2013 02:23 PM

Quote:

Originally Posted by natman589 (Post 7339567)
the squeal is still there, just not as bad as before i took pliers to it, so im going to go at it again and see what i can do.

Also, i had never heard of needing to bed in your parking brake, although it makes sense. i gave it a go 5-6 times, and it doesnt seem to have improved any. since the parking brake does actually hold the car on my driveway, would it be acceptable to simply adjust the parking brake to a tighter level?

Yes. You probably need to adjust the parking brake at each back wheel. Only if this does not do it do you tighten the adjustment at the parking brake handle in the car. Also as jhurless mentioned, you have a bent backing plate. Do not try to bend it back with pliers. You need a small pry bar between the backing plate and the rotor. Wedge it back into place or you will butcher it.

natman589 01-26-2013 09:45 PM

Quote:

Originally Posted by SJBimmer (Post 7339960)
Yes. You probably need to adjust the parking brake at each back wheel. Only if this does not do it do you tighten the adjustment at the parking brake handle in the car. Also as jhurless mentioned, you have a bent backing plate. Do not try to bend it back with pliers. You need a small pry bar between the backing plate and the rotor. Wedge it back into place or you will butcher it.

sounds like a plan. ill tackle it in the next day or two.

as for the backing plate, how necessary is it actually? i dont plan to remove it, just curious really

SJBimmer 01-27-2013 08:43 AM

Quote:

Originally Posted by natman589 (Post 7340611)
sounds like a plan. ill tackle it in the next day or two.

as for the backing plate, how necessary is it actually? i dont plan to remove it, just curious really

It's just to keep large stones, gravel, ect out of the braking system. If it was purely a track car, I would suggest removing them for better brake cooling, but for a street car, I suggest you leave them on.

jvr826 01-27-2013 09:52 AM

Quote:

Originally Posted by natman589 (Post 7339567)
Also, i had never heard of needing to bed in your parking brake, although it makes sense. i gave it a go 5-6 times, and it doesnt seem to have improved any. since the parking brake does actually hold the car on my driveway, would it be acceptable to simply adjust the parking brake to a tighter level?

Did you make any changes to it during the brake job? If not, and it worked well before, keep at the bedding until it works better. I might have done it 10-15 times before I could get mine to hold the car on a hill. If you didn't clean the new rotor with brake-kleen to remove any of the oil coating, then this may also be contributing and require more tries before it will grab well.

You risk making it too tight by adjusting it if it's not needed.


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