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Discussion Starter · #1 ·
Hello- long time viewer- first time poster.

My wifes 2001 325i wagon 80k miles has developed an occasional mild steering wheel viration along with a nasty odor from the front brakes. The odor is only detectable from outside the car and is stronger by the front passenger side rotor. The vibration is barely detectable compared to how it vibrated when the control arm bushings went.

The car was in for service about 2 weeks ago and they flushed the brake fluid. Can air in the brake lines cause vibration in the steering wheel? Where could this odor be coming from. The car is not leaking any fluid externaly and is not make any strange noises.

Front control arms were changed at 40k miles.

thanks for the help
 

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Well depending on how they did the calipers, sometimes calipers stick when pushed back in for changing the pads. So you could have a caliper sticking.
 

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Brakes are fairly simple to diagnose, but we need a bit more info: Does the car stop normally, with no pulling to one side or the other? Is the pedal feel normal? Do you sense any vibration in the brake pedal when the brakes are applied? Is there any discoloration on either of the front rotors?

A stuck caliper can cause the pads to ride on the disk all the time, producing the heat and smell you mention. But without more info, it's difficult to be accurate.
 

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Discussion Starter · #4 ·
Thanks for the info,

I did the rotors and pads myself about 2 months ago. No problems until the dealer did a brake flush as part of routine maintainence / inspection.

the brake pedal feels fine and there is no discoloration. The car stops normally and does not pull to either side. The stuck caliper sounds like a good diagnosis. The probelm seems to come and go randomly. Does not happen everytime she drives the car.


How do I un-stick a caliper? Does it just need to be taken off the rotor and cleaned? Is it possible that both front rotors sometimes stick?
 

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With sliding calipers, there are two possibilities: The first is that the caliper is stuck in the bracket, and does not slide when the brake pedal is pushed. The second is that the hydraulic piston in the caliper is stuck.

Each is easy to check, but you are going to have to remove the wheels, jack up the car, and get your hands dirty here.
 

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^^^

I agree, but it is more likely a sticky hydraulic piston in the caliper. If so, best to just replace the bad caliper. There will be more brake dust build-up on the wheel with the sticky caliper. You may also need to replace or resurface the rotor as well. But, if you get real lucky you can just clean and lubricate the slides that the brake pads ride on.

GL!
 

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another "possiblity" is a failing hydraulic line. If it is collapsing, it may allow pressure to reach the caliper, but not allow it to depressurise sufficinetly, so the caliper thinks the brakes are still applied.
 

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Discussion Starter · #8 ·
I agree, its most likely an intermittant sticky caliper (piston). It only occurs occasionaly and is happening less and less often. It may be working itself out?? I will have to check this weekend to see which side has more brake dust and replace. Do both sides need to be done at the same time-- seems reasonable.

thanks for the info
 

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Discussion Starter · #9 ·
hello again,


the problem has re-surfaced again. Now the odor is confined to the passenger side front wheel. I took the wheel off again and the rotor is discolored and there are "white - orange" lines running around the rotor surface - its not rust. I have been reeding allot about rotor / pad deposition. These are new rotors and I changed the pads myself and definitely did not follow the break-in (had no idea I needed to do that :dunno:) procedure outlined here and many other sites.

Could the vibration be from uneven deposition? If so, how do I correct this problem? Can I replace the pads and re-bed? Or do I need to replace the rotor (Its about 2 months old)?

thanks,

Anthony
 

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Hey Anthony,
Were you able to get rid of this problem of steering wheel vibration and odour? I experienced a very similar thing today morning while driving to work. All of a sudden (within 1 mile of driving) my steering wheel started vibrating. Soon after getting outside the car, I could smell a burning odour, possibly from the pads, on the driver front side wheels. I checked for any leaking fluids or the burn smell from under the hood, but could not find any. This smell did not seem to come from other wheels, either.

FYI: I got the rotors and brake pads changed about 3 months back and haven't had any problems till today.

Bimmer folks: Is there a simple visual way to diagnose the problem? One way I can think of is to see if the pads are continuously sticking to the rotors by comparing the gap to other wheels. Are there other things I could check without taking off the wheel/tire?
 
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