Muddy waters and the bearing blues
Some 2009-2013 Mazda6 vehicles equipped with the 2.5L engine (built before Feb. 15, 2012) and the 3.7L engine (built before July 18, 2012) may exhibit an unusual humming noise from the front wheel bearings. This may be caused by muddy water entering the wheel bearings, resulting in rust. The bearing seal has been improved to eliminate this concern.
With the vehicle on a lift, turn the front wheels by hand to identify the affected side(s).
Perform the wheel bearing excessive play inspection according to the MS3 online instructions or workshop manual section 03-11.
Replace the affected wheel bearing(s). Be sure to replace the retaining clip, dust cover and locknut with new ones during wheel bearing replacement.