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Groan/Hum at Low Speed

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    #1

    Groan/Hum at Low Speed

    I need some help diagnosing a weird noise. It appears to be coming from the front of the car since I can occasionally feel a vibration in the steering wheel. It's an auto (shut up!) and only happens when accelerating from a stop or very low speed and goes away after accelerating past 15-20 miles (my guess, but its a low speed). It appears to only happen once I've driven a few miles. It's a hum or groan that comes and goes (as in hum, hum, hum, hum) and it doesn't matter if you are going straight or turning.

    Front Susp. Parts Replaced:
    tie-rods
    control arms/bushings
    strut/shocks
    E36 ps rack
    hubs/wheel bearings (only parts replaced to fix this problem)

    I replaced everything but the wheel bearings mid last year. When I replaced the wheel bearings a few weeks ago due to this noise I thought the problem was fixed because the noise was gone. Two days later the noise was back. So i thought maybe my brakes were bad (warped rotors, rubbing, etc) but my own visual check and a shops inspection didn't find a problem with the suspension or brakes.
    The weird thing is that after I got the car back from the shop the noise was gone for the entire day, just like when I replaced the wheel bearings. On my way to the shop, noise. After the shop, no noise... until the following day.
    In both cases the front was lifted to remove the wheels. Could this be a weight shifting issue? I bring this up because someone may recommend that my guibo, csb or driveshaft may need to be inspected but I just have trouble linking these parts to the noise when I feel it in the steering wheel and the noise was "gone" after the front was inspected. I should mention that I don't get the clunks that people experience with a bad csb or driveshaft.
    So any clues? Any and all help is appreciated. Thanks.
    Tags: None
    #2
    tranny mount?
    '87 325i "Chewey" (RIP, my beloved)
    current:
    '01 e46 325iT "Dot" - #datwagonlife
    '87 e30 325i "Tui" - she has her mother's eyes

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      #3
      I had an e34 that did this in reverse (on deceleration below 10 mph or so) that turned out to be a bad universal joint on the driveshaft. It doesn't necessarily cause a clunk. I could feel it in the steering wheel and everything. It's worth checking.

      Edit: just realized this could be confusing. It didn't do it when I was going in reverse.
      Last edited by mistertonylee; 06-02-2011, 07:09 AM.

      Comment

        #4
        I think my first suspect would be the power steering.
        The car makes it possible, but the driver makes it happen.
        Jim Levie, Huntsville, AL

        Comment

          #5
          Sorry for not getting back sooner.

          What, exactly, about the power steering would you suspect? I did swap the stock rack with an e36 rack a few months ago. No issues steering and the noise isn't there at higher speeds. Also makes no difference if I'm driving straight or turning.

          And I thought about the driveshaft u-joint as well but I can "feel" the noise in the front, left driver side.

          One thing I am noticing is that the noise will go away if I brake. If I step on the brake pedal the noise will go away and will come back when I release the brake pedal (all at low speed). The brakes don't feel bad though. I noticed this a few days ago. However, the shop didn't find anything wrong with my brake set up.

          The real pain in the ass is that I don't have room in my garage to do any type of inspection on my car. I really want to get underneath the car to re-check my brakes and also the guibo, csb and driveshaft but until I get my parts car out of my garage I have to live with this annoying noise. Im kind of using all of your suggestions as a what-to-check list when I do get under there.

          Comment

            #6
            One thing I am noticing is that the noise will go away if I brake. If I step on the brake pedal the noise will go away and will come back when I release the brake pedal (all at low speed). The brakes don't feel bad though. I noticed this a few days ago. However, the shop didn't find anything wrong with my brake set up.
            That changes things and makes me change my mind about the prime suspect. If the car is traveling in a straight line and the use of the brakes makes the noise go away or come back, I'd look to the wheel bearing (even a new part can be bad), caliper, or backing plate. A sticking caliper could do this or if the backing plate were lightly rubbing on the rotor application of the brakes could flex the rotor away from the backing plate.
            The car makes it possible, but the driver makes it happen.
            Jim Levie, Huntsville, AL

            Comment

              #7
              Thanks, Jim. I'm seriously starting to suspect my brakes as well. I have heard that even new wheel bearings may be bad but the noise is coming from the same general area as before. And the fact that the noise goes away after I "mess around" with the wheel and brakes leads me to believe that it must be in the brake area.

              Do you know if heat plays a role in causing a caliper to stick? Like I mentioned before, the noise is not there when the car has not moved for a while. I will usually notice this noise in the morning or after leaving work in the afternoon, once the car has been driven for a few miles.

              Now, if I could only fast-forward a few weeks so that my parts car is stripped and removed from my garage I would be a happy man.

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