Mud Makes Mazda Hum
Some 2009-2013 Mazda6 vehicles may exhibit an unusual humming noise from the front wheel bearings. This may be caused by muddy water entering the wheel bearings, which causes rust.
The bearing seal has been improved to eliminate this concern. Replace the affected wheel bearings with P/N GS3L-33-047A for vehicles equipped with a 2.5L engine; or GS4H-33-047A with a 3.7L engine.
When front wheel bearings are replaced, Kia also recommends replacing the retaining clip, locknut and dust cover.