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X3 brake "chatter" while driving

Discussion in 'E83 X3 (2004-2010)' started by Igor, May 29, 2012.

    • Member

    Igor

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    I recently purchased a 2008 BMW X3 with 31k miles on it. Within a few days of owning it, the front shock started leaking. Although the car was no longer under warranty, the dealer took care of the problem and replaced the front shocks. So I pick up the car and start driving it home on the freeway. About 3 to 4 miles into the trip, the car starts shaking and vibrating. Thinking one of the wheels is loose, I pull over and inspect the car. No issues. No warning lights. Nothing.

    I limp the car back to the dealer. Upon closer inspection, it appears that the breaks are “pulsing” on/off causing the car to vibrate. The symptom becomes more obvious at 40mph+. When I finally get back to the dealer, the brake smell is very pronounced (I did not check which rotor/rotors got hot though). Now I'm thinking that during the shock replacement, someone messed up one of the wheel sensors. Once the ABS/traction control system got confused, it started pulsing the brakes. However, I would have expected some warning light. Since there is no light, I’m thinking it’s the ABS – note, however, that the pulsing was subtle enough where it could not be felt in the brake pedal itself.

    I get a call back from the dealer today and their diagnosis is “bad e-brake cable and rear rotors”. Certainly might explain the lack of warning lights but really, e-brake cable and rotors? The car had no break shimmying when braking and had great stopping performance before the shock service. How can the e-brake be pulsing the brakes even if the cable was bad? Any insight would be greatly appreciated. I usually do most of the work on my cars and this one makes no sense.
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    MGarrison

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    Weird - good question for Mike Miller. Me, I'd suspect something related to what they worked on, ie - the front. Bad ABS sensor, broken sensor wire (or, broken internally, presumably within the length that's in the wheel-well to the strut), or something that would cause the ABS to go nuts. I'd ask how they came to their diagnosis. If all they did is plug in the computer and are relaying what the computer says, the question is why would they trust the computer considering what was just done, & why wouldn't they physically examine the front by getting it on a lift and pulling the front wheels and checking all front ABS plugs/wire/connections/sensors at least visually? Then, the next question is how did they isolate this issue and ID it to the back, where no work was done (assuming no work to the rear brakes _was_ done)? Any possibility of a haywire ABS ecu/brain? I'd ask them if they think if the diagnosis makes sense in light of what work was just completed - also, get a clear understanding of what they'll intend to do to fix the problem if their diagnosis is wrong, and you've paid for the work based on the wrong diagnosis - will you be on the hook again for another service bill if they get it wrong the next time, or just what? I'm no X3 expert (hey, there's a personalized X3 plate - XP3RT), so I'd hold out the possibility their diagnosis is correct - but, like you, seems odd to me since the brake work just completed was at the front end.
    • Member

    Igor

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    Thank you for the feedback. Just to close this one out, the dealer was correct. After replacing the e-brake cable and rear rotos (with pads), all returned back to normal. Apparently, when the car was in for the front shock service, the technician used the e-brake. A loose aftermarket stereo box in the center console caused the right rear cable from not releasing. After a few miles on the highway, once the rotor started glowing red, it warped causing the chatter.
    • Member

    MGarrison

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    The game of "Clue" solution then is that Mr. Aftermarket Stereo Box did it in the console with the cable...

    Appreciate the update!

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