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EricFromCT
EricFromCT, Auto Technician
Category: Mazda
Satisfied Customers: 3411
Experience:  20 years dealership experienceASE Certified L1-L2
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Look isolating a steady-state low pitch whine from left side

Customer Question

Hi,
Look for help isolating a steady-state low pitch whine from left side front that presents as classic worn wheel bearings on a 2009 CX-9.
My mechanic replaced wheel bearings twice with no improvement (second time with new hub). Now a different mech suggests the knuckle may not be cylindrical and wants to replace it with yet another bearing. I don't believe its the knuckle. How should this be properly diagnosed and shouldn't a dealer have the micrometers and acoustic tools to properly isolate the humming What else presents like a worn bearing, dissapates when turning (carrier bearing?) Thanks
Submitted: 1 year ago.
Category: Mazda
Expert:  EricFromCT replied 1 year ago.

Hi. Is your Mazda 2wd or 4wd?

Customer: replied 1 year ago.
2wd
Expert:  EricFromCT replied 1 year ago.

Ok. Thanks. I agree with you. It is common for the carrier bearing for the axle to cause this noise. I never heard of a knuckle being out of round causing this. They need to make sure they are replacing the correct bearing to start with. And if all the bearings have been replaced then they need to check the carrier.

Customer: replied 1 year ago.
Thanks. I'm sure the mechanic is guessing at this point. I assume it's not much more effort to replace the carrier bearing while the wheel bearing is being replaced? Curious if there's any half shaft condition you've seen that replicates a worn wheel bearing? If the half shaft was out of balance, I assume the humming wouldn't be steady state or would completely dissipate while turning. I hate throwing away a lot of hard earned money on pure guessing games.
Expert:  EricFromCT replied 1 year ago.

I understand. an axle would not replicate a wheel bearing type noise. tires would replicate that. but that can easily be determined by driving the car on the lift and seeing if the noise goes away. the carrier bearing is easy to change. does not matter if you were doing the wheel bearing or not. thank you

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