Analyzing a Failed Bearing
Wheel Bearings can be inspected and a fault diagnosis can be made on why a wheel bearing has failed. Finding the source of the problem is important to make sure that the same problem does not cause the new wheel bearings to fail. Analyzing a failed bearing starts by removing the faulty wheel bearing and cleaning it thoroughly. When the bearing is clean a visual inspection needs to be done on all parts of the bearing. This will tell you the cause of failure.
If the bearing rolling elements and race surfaces show signs of rust or corrosion, you will need to inspect and replace the grease seals as well as the complete bearing assembly. If the bearing is so worn and there are metal shavings in the grease and wheel hub, a thorough cleaning of the wheel hub and stub axle shaft will need to be done with a suitable solvent so all those metal shavings are removed so none are left to destroy the new wheel bearing.
If you get a condition called Brinelling which causes the wheel bearing to be extremely noisy during operation, which is caused by damage to the bearing race when fitting or removing the bearing. Brinelling is identified by tiny dents on the rolling elements of the bearing, and excessive shock loading on the bearing.
Other wheel bearing failures occur when the outer or inner race either spin in the wheel hub or spin on the stub axle. This can lead to extensive damage of the wheel hub or stub axle. These components will then have to be replaced. Be sure to visually inspect the wheel hub and stub axle for damage every time the wheel bearings are serviced or replaced.
Repacking, Adjusting and Installing Wheel Bearings.
Wheel bearings should be serviced and checked at regular intervals according to the manufactures maintenance times or vehicle mileage. Another suggestion is if you are replacing brakes it is a good idea to check and repack the wheel bearings too. Make sure that only the recommended grease for your vehicle is used. Also, avoid mixing different types of greases by thoroughly cleaning all the old grease from the hub and wheel bearings.
When reinstalling wheel bearings it is important to follow the vehicle manufactures procedure. Always use new grease seals and split pins. This will prevent grease leaks and external contamination from entering into the new grease and bearings. The new split pin will prevent the adjusting nut from loosening off and causing an unsafe driving condition.
Removing, Cleaning and Inspecting Wheel Bearings.
Firstly remove the wheel bearing dust cap with a pair of adjustable pliers.
Then remove the locking mechanism. There are generally 2 types. There is either a split pin or a locking plate. The locking plate will need to be straightened so that a wrench can be placed on the outer of the two lock nuts to be loosened. Remove the split pin or outer lock nut to get to the adjusting nut.
Then remove the adjusting nut, the keyed washer, and outer bearing.
Refit the adjusting nut at least the with of the nut or about 5 turns back onto the stub axle spindle.
Now hold the drum at 11 o’clock and 5 o’clock and while putting upward and downward pressure, pull the drum towards you. The adjusting nut will stop the drum from flying off, but the inner bearing race and grease seal will be dislodged from there seat on the stub axle. Now remove the adjusting nut and drum assembly.
Now you will have to remove the grease seal from the hub to get to the inner bearing. Take an old rag and wipe off the grease from both bearings and do a quick visual inspection for damage. If there is damage you know that they need to be replaced but don’t forget to identify what caused the damage.
If the bearings look like they can be used again, then clean them, the races and hub thoroughly. When using a solvent to clean these parts make sure there is no grease left on the parts as this will mix with the new grease, and you won’t be able to do a final inspection correctly. Now do a final inspection to be sure you can reuse these bearings again.
Never rinse a bearing off with water as this will cause flash rust and pitting off the bearing. Never blow a bearing dry with compressed air because condensation is passed through the airline which will get onto the bearing and cause flash rust and pitting. Allow the bearing to dry in the sun before inspection.
How to Grease a Bearing by Hand.
Use a pair of latex gloves to protect your hands from the grease.
Put a golfball size glob of grease in the palm of your non-dominant hand.
Put the index finger of your other hand through the center hole of the bearing with the bigger diameter of the bearing facing down.
Force the bigger diameter of the bearing through the grease until it touches your hand. This will force grease in-between the rolling elements, bearing cage and bearing race. Continue this process until the grease comes out at the top of the bearing.
Then turn the bearing and repeat the process until the grease pushes through all the spaces in the bearing. Also, smear some grease on the outside of the rolling elements. Repeat this process for all bearings that need to be greased.
How To Replace the Bearing Race in the Hub.
Firstly remember to use safety glasses when replacing bearing races in the hub. Wheel bearings and races only need to be replaced when they are damaged. If one part of a wheel bearing is damaged, then all parts must be replaced especially a tapered roller bearing that is made in two pieces. With these bearings, the outer race is usually press-fitted into the hub and will need to be driven or pressed out and a new race pressed in. It is very important to make sure the seat in the in the hub is clean, with no burrs, so the new race will seat properly or else there will be a premature bearing failure.
The correct way to remove the bearing cones is to use a hydraulic press with the correct size dollys. If you don’t have this equipment then the next bet is a punch and hammer. Normally the hub will have small slots in the casting shoulder where the bearing race stops against, that allows a punch to sit on the back of the race to knock it out.
Clean the inside of the hub with a suitable solvent. Visually inspect the race seat for burrs. If there are burrs then dress them off with a metal file.
When installing the new ones use the old races to knock against so the new bearing races are not damaged. Press or knock the new races in until they are fully seated in the hub. When using a hammer and punch you should hear a sharp metallic sound then you know the race is fully seated. Verify by a visual inspection to be sure the race is fully seated. Repeat this process for all the bearing races that need to be replaced.
Installing Wheel Bearings.
Place the inner wheel bearing in its race. The narrow side facing towards the race.
Install the new grease seal. Use a seal driver or tap it in with a hammer, making sure the seal is installed straight. Put a little bit of grease on the seal lip for initial lubrication.
Remember to put a small amount of grease in the center of the hub. This is to ensure that the bearings are always fed with grease.
Carefully fit the hub over the stub axle spindle making sure that the inner bearing fully seats against the spindle flange. Install the outer bearing on the stub axle spindle and into the race.
Fit the keyed washer and adjusting nut on the spindle then tighten until finger tight. Then tighten the adjusting nut to the specified torque while turning the drum. This seats the bearings correctly in their races and squeezes the excess grease from between the bearings and races while seating the bearings.
Important is now to loosen the adjusting nut one quarter turn without turning the drum, and then retighten the adjusting nut to the specified torque.
Install the Locking Mechanism.
If you have a split type, insert the new split pin through the castled nut and spindle. If the holes don’t line up then turn the adjusting nut clockwise until the very next hole lines up. You won’t have to turn much. The long leg of the split pin should be facing towards you.
When the split pin is fully engaged in the notch, bend the long leg towards you and up and over the end of the spindle. Make sure the split pin does not touch the inside of dust cap. If it does cut the excess off with wire cutters.
If you have the tag style locking device, then place the tang washer against the adjusting nut and then turn the lock nut up against it. Torque the lock nut to the specified torque and bend the tang towards you and against a flat side of the locking nut with a small pry bar or big flat screwdriver to lock the adjustment.
If you have a locking nut style, then tighten the lock nut to the specified torque.
Install the dust cap. Make sure it is fully seated in the hub. Also, make sure the hub turns freely with no play nor any unusual noises.