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Odd noise at speed, help please!

Discussion in 'Gen 2 Prius Technical Discussion' started by tomellis, Oct 3, 2016.

  1. tomellis

    tomellis Junior Member

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    About two weeks ago I took my 2005 Prius up a mountain road that turned out to be much steeper than I had thought. Too narrow to turn around until I had gone quite a ways up (more than a mile), I went slowly and the car seemed to do fine. Because the road was both very steep and fairly long I put the transmission into B mode on the way down to help brake with the engine so I wouldn't burn out the brakes. Probably the only time I have ever driven in B mode. Once off the hill I put the car back into D before continuing.

    On the drive home I thought I was hearing/feeling a noise at freeway speeds that I had not heard before. Very much related to the speed of the car, almost sounded like a conventional engine turning high RPMs. However, the noise was there whether the engine was running or not, even going downhill. Mileage on the trip was good, ~50MPG for 150 plus mile run.

    Since then I have noticed the same noise whenever I drive the car at speed. First start to hear it at ~40mph, and the pitch/volume increases as I go faster. When I intentionally force the engine to turn on and run hard, the noise is still there and is clearly a separate sound. Definitely a function of how fast the wheels are turning. And I am not certain, but I think my mileage has dropped off. I usually get ~45 MPG for my usual driving but now am getting closer to 40. But not enough distance to be sure that is really happening.

    No warning lights of any kind. I have not yet had a chance to plug in an OBD but plan to borrow one from a friend and see what codes show up.

    I would very much like to hear any ideas anyone has for what is going on here. I am afraid I have damaged the tranny, but if anyone has other thoughts, or is just able to confirm my fears, I'd like to hear your thoughts.

    Thanks in advance for any help!
     
    #1 tomellis, Oct 3, 2016
  2. fotomoto

    fotomoto Senior Member

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    A common wear item on the prius that causes funky noises are wheel bearings. I would check them first. The hard mountain drive may have been the straw that broke the camels' back.
     
    #2 fotomoto, Oct 3, 2016
  3. tomellis

    tomellis Junior Member

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    Any hints for best ways to check the bearings?
     
    #3 tomellis, Oct 3, 2016
  4. tomellis

    tomellis Junior Member

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    Any hints for best ways to check the bearings?
     
    #4 tomellis, Oct 3, 2016
  5. bisco

    bisco cookie crumbler

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    how many miles on her?
     
    #5 bisco, Oct 3, 2016
  6. tomellis

    tomellis Junior Member

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    Just over 90k. Spent first 5 years in New England with my wife's parents, less than 30k when we got her.
     
    #6 tomellis, Oct 3, 2016
  7. ILuvMyPriusToo

    ILuvMyPriusToo Senior Member

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    If you have access to a lift, get the wheels off the ground and turn them. A mechanics stethoscope or piece of tubing can help you hear if it isn't running smoothly.

    Also possible you have a frozen brake caliper that is dragging. That might affect the mileage more than a noisy bearing. (I had a bad front bearing - to the point where you had to raise your voice to talk in the car - but mileage was still OK). Feel your wheel hubs (carefully) after driving and see if they get hot.

    There is no DTC code associated with either condition, so the reader may not be informative.
     
    #7 ILuvMyPriusToo, Oct 3, 2016
  8. ILuvMyPriusToo

    ILuvMyPriusToo Senior Member

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    My bad bearing had to be replaced around 65K, and others have had issues before 90K too.

    Winter weather with salt can be rough on both the brakes and the bearings.
     
    #8 ILuvMyPriusToo, Oct 3, 2016
  9. tomellis

    tomellis Junior Member

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    Sounds like I need to get the car up in the air and see how much noise/roughness there is when I spin the wheels. Sure would rather have this be the issue rather than the transmission!

    Car has been in Seattle for last 6 years, but those first few years in New England may have given everything plenty of salt. Thanks for your suggestion, I'll report back after I check out the bearings and brakes.
     
    #9 tomellis, Oct 3, 2016
  10. ILuvMyPriusToo

    ILuvMyPriusToo Senior Member

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    Good luck!
     
    #10 ILuvMyPriusToo, Oct 3, 2016
  11. ILuvMyPriusToo

    ILuvMyPriusToo Senior Member

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    Folks here would tell you that it might be a good time (anyway) to change your CVT fluid (if you haven't done so before), and that would let you check the drain plug for any metal shavings. But I would try to sort out your current issue by checking the axle/bearings/brakes before addressing anything else.
     
    #11 ILuvMyPriusToo, Oct 3, 2016
  12. greasemonkey007

    greasemonkey007 Active Member

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    You dont necessarily have to get it on a lift. You can jack up one front wheel, set the park brake, and put it in drive, preferably with the aid of an assistant. Then you can listen to each side separately, as only the wheel in the air will be turning. Listen for a growling or a roaring sound.
     
    #12 greasemonkey007, Oct 4, 2016
  13. valde3

    valde3 Senior Member

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    Faulty wheel bearing can also be lose. My (front) wheel bearing didn’t even make much noise but I could easily tell it being lose by just jacking the wheel up. And then when pressing brake pedal the looseness disappeared which tells you clearly that it’s faulty bearing. After removing the knuckle (with bearing) I could also tell that bearing was notchy.

    My method of testing for brake drag:
    Drive something like 10km or 6miles without touching the brake pedal and then stopping without brake pedal (In a Prius you can use B to slow down and then reverse to stop completely). Brakes should be cool. But test the rim then the caliber and only then the disk to avoid burning yourself.
     
    #13 valde3, Oct 5, 2016
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