Problem:
Coming up with an accurate diagnosis for unitized style wheel bearing.
Cause:
The sealed design of the wheel bearing sometimes makes identifying which bearing is the source of the complaint difficult.
Solution:
There are several techniques available that can help pinpoint a failing bearing. They are listed below:
Test Drive
Wheel bearings can cause many different types of noises when driving. The noise will usually be more pronounced when the bearing is in a loaded condition, such as during a turn.
Vibration Test
Failing wheel bearings will often cause a roughness during wheel rotation. The vehicle’s strut and spring act like an amplifier and allow easy diagnosis of a rough bearing. Place your hand on the spring and rotate the wheel assembly. A rough bearing will produce a pronounced vibration through the spring. Repeat the procedure on the opposite side.
Stethoscope Test
Failing bearings will often make a noise when they start to fail. The noise is not always easy to identify. The use of a stethoscope can make pinpointing the problem bearing easier. Once the vehicle is both on the rack and in gear, you can use the stethoscope. Start by placing the stethoscope on the knuckle as close to the bearing as possible. If the bearing is failing, it will produce a noticeable hum or grinding sound. It may be necessary to turn the wheel slightly to duplicate the bearing noise on the rack.
Caution: It is essential to take extreme care when working near a rotating wheel.
Isolation Test
In some cases, it will be necessary to isolate the bearing to determine its condition. For instance, for most FWD vehicles, this is a relatively straightforward process. First, remove the caliper and rotor. Next, disconnect the outer tie rod end and low ball joint. Continue by removing the CV axle nut. Next, disconnect the knuckle from the lower ball joint and remove the CV joint from the hub. The bearing is now isolated. Finally, rotate the bearing while feeling for roughness.
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