Diagnose and replace a worn wheel bearing
Diagnosing a worn wheel bearing can be tricky. Many worn wheel bearings make noise
but others don’t. When noise is present, the bearing can make any of these sounds: snapping, grinding, knocking, or growling. However, worn suspension components and tires can also make these same sounds. So your job is to isolate the noise. Once way to do that is to drive the vehicle on a straight flat road and establish a baseline noise. Then turn the vehicle to see if the noise changes. Also increase and decrease speed to see if the noise changes with speed.
Check wheel bearing end play
Some wheel bearings have worn to the point where they have excessive endplay that causes vibration in the steering wheel and inability to keep the car going in a straight line. Sometimes, excessive wheel bearing wear can cause problems with the ABS wheel speed sensor, where you’ll get an intermittent ABS trouble light due to dropped out wheel speed sensor signals.
Check a wheel bearing with an automotive stethoscope
With the vehicle on jack stands, rotate the wheel by hand and listen for bearing noise. If you hear noise, use and automotive stethoscope to find the location of the noise. Touch the stethoscope probe to the steering knuckle. Read this post on how to use an automotive stethoscope
Check the wheel bearing for play
Grab the tire at the 2:00 and 6:00 o’clock position and pull and push to detect hub movement. Don’t confuse rubber movement with hub movement.
Then move your hands to the 3:00 and 6:00 o’clock positions and repeat.
Check for wheel bearing seal leakage
Many wheel bearings are permanently sealed. But if the seal deteriorates, the grease will leak out. So check for signs of grease leaking from the bearing. A wheel bearing with seals should never show signs of leakage. If it does, it’s bad. Any seal that’s leaking grease is a seal that’s also allowing water to enter the bearing.
How to replace a worn wheel bearing
If the hub bearing is a unit bearing assembly, you must replace the entire unit. Remove the axle nut (on a front wheel drive vehicle), and then remove the hub retaining bolts. You
may have to pry the old unit out from the knuckle.
If the wheel bearing is pressed into the knuckle, you must rent the proper tools (like a hub tamer)to remove it or remove the entire knuckle and take it to a machine shop and pay them to swap out the bearings.
Tightening the axle nut
Always replace the axle nut with a new part. The single biggest mistake you can make when reassembling the new bearing is to use an impact wrench to tighten the axle nut. The rapid impacts can chip the chrome plating off the roller or ball bearings and can damage the internal races. You won’t notice the damage right away, but the bearing will fail early due to damage you caused with your impact wrench.
So tighten the axle nut by hand using a ratchet and socket to seat the nut. Then use a torque wrench to set the pre-load according to spec. Failure to use a torque wrench can cause premature bearing failure!! Proper preload is critical! If the preload is less than spec, the bearing can separate.
What causes a wheel bearing to fail? See this post
©, 2015 Rick Muscoplat
Posted on by Rick Muscoplat