1998 Toyota Camry • 4 cylinder FWD Automatic • 120,000 miles

I have a Camry 98 XLE 4 cyl. Recently, I had the front left hub bearing replaced to fix the rattling noise when I drive the car. However, noise still exists. The mechanic said that he found that the contact between the bearing and the knuckle was somewhat loose after he replaced the bearing and couldn’t make the noise completely gone. He recommended having the knuckle replaced as well, but I didn’t have. Dose the worn knuckle often make the wheel rattling noise? (One note is that the bearing I had replacement with was an aftermarket part that was said to be compatible to both Solara and Camry.)
Thanks ahead for the advice.
April 7, 2011.

Wheel bearings don't make rattling noises. They hum like an airplane engine when they get noisy. Something has been overlooked. There is a tool called a "Chassis Ear" that is real helpful in finding noises. It is six microphones, a switch box, and head phones. You clip the microphones to suspect points, then listen and switch between them while driving. Be aware that many mechanics have never heard of or even seen this tool.

Loose brake pads and worn anti-sway bar links commonly rattle. The brake pads will stop rattling anytime you have light pedal pressure applied. Anti-sway bar links aren't real serious but they do affect how a car corners. Metal shields can work loose too.

Apr 7, 2011.
I should have used the correct word. The noise is more like airplane hum. It sounds only when the wheel is rotating. The faster the car is running, the faster and louder the hum sounds. I feel the noise is a bit louder when the car is turning right or left.

That is typical of a wheel bearing. On cars with the more expensive but easier-to-replace bolt-on style, it is almost impossible to determine which side is the noisy one. It can sound like the left side, it can get louder when turning slightly right, (more weight is transferred onto the left side), and it can still turn out to be the right bearing.

The only reliable way to tell for sure is to run it in gear on a hoist and listen next to each one with a stethoscope.

The single biggest cause of repeat bearing failure is improper installation procedures. It is absolutely critical that no vehicle weight be placed on the bearing until the axle nut is tightened to specs. The outer cv joint / stub axle is what holds the bearing together. Some people install the wheel and set the car down on the tire to hold it from turning so they can torque the axle nut. At that point the damage has already been done.

Apr 8, 2011.
Actually, I had both of the front hub bearings replaced. I had had a wheel hum a year ago, and had the front right bearing replaced. The humming noise was completely gone at that time.

Since about a month ago however, I started hearing the humming on the left side. I had the front left bearing replaced as well. However, this time the humming noise is not gone after the replacement. The mechanic said that he found that the contact between the bearing and the knuckle was somewhat loose after the replacement. He suspected the knucke is worn due to age and recommended the knuckle to be replaced as well.

My quest is whether the real cause is the knuckle or not. Dose the worn knuckle often make the humming noise? Or, do you know any missing imprortant check points that the mechanic missed checking. (One note is that the bearing I had the replacement with was an aftermarket part that was said to be compatible to both Solara and Camry.)

The front bearing is still a pressed-in design that has to fit tightly in the spindle. It's hard to believe the new one is loose because it would be wobbling around and spinning, and that would continue to eat the spindle away. You would hear knocking and rattling, and that wheel would wobble around when you grab it and tug back and forth sideways on it. That wear would continue to worsen over time, but that alone won't cause a hum. The hum comes from tiny dents in the bearing "races". Those are the two smooth hardened steel surfaces the steel marbles or rollers ride on. Those dents develop from an impact such as hitting a pot hole really hard, or when the bearing isn't held together tightly with the axle nut.

If the bearing assembly really was loose in the knuckle, both mating surfaces will be very shiny from the polishing action the parts created when they moved across each other, or they will be rough and chewed up if there was excessive movement taking place between them. Normally the bearing and the hole in the knuckle will be a dull gray or silver color and there will be very small scratches going straight in and out from the previous removal and installation of the bearing. Those are some clues to tell if the bearing assembly was loose in the knuckle. There is also going to be a plate that bolts on to hold the pressed-in bearing from working its way out. That plate will have a shiny ring where the bearing ground the surface rust off if it really was loose. That still would not cause the humming sound though. It's hard to say for sure, but for such an early repeat failure, I would be thinking the axle nut wasn't tightened to the proper value. A lot of do-it-yourselfers set the car down on the tire to hold the axle from spinning so they can tighten that nut with a torque wrench. At that point the damage has been done to the new bearing.

For the noise to not return for a year suggests the nut was tightened but not enough or the old axle nut was reused. Your bearing comes with a new nut. Some of them are a "torque-to-yield" design which means tightening it stresses it to a calculated, designed-in amount. That can only be done once. When that type of nut is reused, you MIGHT get lucky and not have problems, but it isn't worth taking the chance.

Apr 11, 2011.
I appreciate your detailed explanation. I'll check them.

One last question is about a seal ring. Does Camry 98 XLE 4 cyl need a seal ring in between the bearing and the knuckle. I heard the older model of Camry needs a seal ring between them.

The bearings are sealed assemblies. Grease can't get out and dirt and water can't, ... Well, ... Isn't supposed to get in. Once the bearing is pressed in place, another seal is tapped in behind it. Its lip seal runs on a smooth machined surface on the cv joint. If by chance someone forgot to install that seal, I would guess the life of the bearing might be reduced by about five percent. The bearing won't die a sudden death because of a missing seal but it won't help it any either.

The bearing doesn't have to be removed to install a new seal. Just the cv joint / axle has to be removed. That seal is more of a dust shield. It is not as important as, say the lip seals in a water pump or brake master cylinder. If you drive through deep water, that seal can hold the water out of the bearing for a little while, but there is no matching seal on the other side. Water can seep past the plate that holds the bearing in place but typically you would have to park, (get stalled) in that deep water for a long period of time.

Apr 12, 2011.
I appreciate your answer.