Horrible vibration/rattling when braking, mechanics can't figure out

Maintenance/Repairs
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1

I drive a 2006 Chevy Cobalt. I will simply list the symptoms I am experiencing:

  1. I get a horrible vibration/rattling sound in the front end of my car when I use my brakes.
  2. This vibration can be felt in the steering wheel and the clutch pedal
  3. The intensity of the vibration and the loudness of the rattling are greatest when I brake while going between approximately 40mph and 55mph. For example, if I am driving at 70mph and use my brakes, as my speed falls from 70mph to 55mph the vibration and rattling sound are minimal, perhaps even nearly nonexistent. However, as my speed approaches 55mph, the vibration and rattling sound intensify dramatically, and it’s not just the strength of the vibration, but also the rapidity at which it occurs. Then, as my speed falls from 40mph, the vibration and rattling sound dramatically fall off, quickly becoming nonexistent.
  4. The vibration/rattling is better or worse at a given speed depending on the terrain I’m driving on. For example, braking from 55mph to stopped on one stretch of road might cause intense vibration, while braking from 55mph to stopped on a different stretch of road might cause a vibration that is only half as intense. This can be the case even when there is seemingly no difference between the two stretches of road.
  5. Slowing the car by downshifting does not cause this vibration or rattling sound.

I have had the car looked at by my mechanics. I had two brand new tires put on the front of my car, and I had my alignment done. The mechanics said that my passenger side front rotor was bad, but seemed to think that the vibration was too intense to be caused by the bad rotor. They are baffled as they said they can’t find anything that is loose or that would be causing the problem.

Any help on where to have them look would be greatly, GREATLY appreciated.

2

Didn’t any of your mechanics mention–and investigate–the possibility of an ABS malfunction?

3

They did not. Would an ABS malfunction cause the symptoms described above? I’m not really sure if my car has ABS.

4

I don’t know of a single REAL mechanic that would brush off a rotor that looks bad as not being the cause of a severe vibration while braking.

Sounds like you need a new mechanic.

Tester

3 Likes
5

Yes, your car came from the factory with standard ABS.
And, yes, an ABS malfunction could produce those symptoms, as could rotors that are in need of replacement.

I think that you need a new mechanic.

6

Thanks for the replies to both of you. I’ll go ahead and get my rotors and brake pads replaced and see if that solves the problem.

7

That sounds like a good step forward. It sounds like you need that job done anyway. If that doesn’t do the trick, on many cars the ABS can be temporarily disabled – removing its fuse for example – to prove or disprove it being the source. Loose or missing lug nuts, faulty wheel bearings, loose or faulty brake calipers, and loose steering and suspension parts can contribute to this symptom too.

8

That’s the dumbest thing I have ever heard. Even a slide rotor warp, unseen to the eye, will cause exactly what you are describing.