Have you ever noticed whining or grinding noises coming from underneath your car while driving down the road? If you heard something like this, chances are that one of the wheel bearings in your car is going bad. While replacing a wheel bearing is not that hard at all, tracking down the source of any noise can be tricky. Different issues within different components can sometimes sound similar. This can confuse and throw off-track even the most seasoned mechanics, which leads to unnecessary repairs. Luckily, there’s a couple of tricks that mechanics use to identify and locate a bad bearing. To help you with that, we have created this quick guide about the most common bad wheel bearing symptoms, how bearing works, and how to tell if you have a bad one.
What is a wheel bearing?
First things first. When you are driving down the road, your car travels in a linear motion while the wheels are rotating. Wheel bearings are the meeting point where these two motions come together, and this makes them very important. Although simple and quite reliable, they can cause a lot of trouble if you ignore early warning signs of upcoming failure.
Despite the differences in overall appearance because of their applications, all wheel bearings have similar components and operate in the same way. There is an outer race that is pressed inside the wheel hub and stationary, while the inner race rotates around the knuckle. Between these two races, there is a set of rolling elements, which can be steel balls or cylinders. Their task is to make the movement as smooth and effortless as possible. The grease packed inside the bearing makes this possible, as it reduces friction between moving parts and keeps the temperature down. A rubber or Teflon seal on each side completes the unit. The seal keeps the grease inside and stops the dust and water from coming in. When a bearing goes bad, it’s usually because the seal has failed to do its job.
What are the most common bad wheel bearing symptoms?
During their lifespan, wheel bearings have to cope with high rotational speeds and mechanical forces caused by potholes, curbs, and similar road obstacles. With time, these harsh conditions can take their toll, and the wheel bearing will fail. However, this is usually a gradual process, meaning you can recognize it in its initial phases.
The first warning sign you should notice is a humming noise appearing mostly at high speed. As with any wheel related noise, it will be more apparent as you drive faster. To make sure the sound is coming from the powertrain, check if it goes up and down as the speed of your car changes.
Wheel bearing noises will also sound louder when their load applied to the bearing. To test it quickly, drive around 30-40 mph and swerve from left to right and see if the noise comes and goes. If it does, you definitely have a bad wheel bearing. Doing so will also help you pinpoint on which side the faulty bearing is. The worn bearing will grind more when a load is applied. If you hear the noise louder when swerving right, it’s on the left side and vice versa.
How to check wheel bearing?
The first thing to do when suspecting a bad wheel bearing during a road test is to rule out any other possible faulty component causing the noise. A faulty tire, for example, can create a similar noise so make sure to rule this out before blaming the bearing. Rotate the tires or switch them from side to side and take the car out for another spin. If the noise changes side, the problem is with the tires and not the bearings.
Using a stethoscope
Once you are sure the noise actually comes from a bearing, life the car on a hoist or jack stands. The easiest way to identify a faulty bearing is by using an automotive stethoscope. Start by placing the tip of the stethoscope as close to the bearing as possible. Right around the bearing is best but if there’s not enough space, simply place it on the knuckle. If you are using a hoist and the suspected bearing is on a drive wheel, raise the car, ask a helper to put it in Drive, and step on the gas until it reaches 30-40 mph. If you are using jack stands or the suspected bearing is on an idler wheel, you’ll need to spin it by hand. While the wheel is turning, listen for any grinding or humming noises.
When in doubt, don’t hesitate to compare what you hear with the other wheels. If one of the bearings is grinding louder than the others, it probably needs to be replaced.
Using a screwdriver
If you don’t have a stethoscope, you can also use a big flathead screwdriver or a long ratchet extension. Simply place it like you would place a stethoscope and place your ear at the end. A screwdriver or any long metal rod will work just as well as a professional stethoscope if only that it’s sometimes a little more complicated to place. Stethoscopes are flexible making it easier to get through the suspension and steering system components.
Using your hands
Thanks to noise induction principles, another technique can be used. Since noise and vibrations travel through metal parts you can also put your hand on the suspension coil and see if you can feel vibrations while the wheel is turning. This technique works especially well when using a hoist and testing a bearing on drive wheels. It’s super easy and a lot quicker to just compare the vibration in the coils of the same axle and also requires no tools at all.
Another thing to check is if there is any play within the bearing itself by doing a quick shake test. To do this, you need to grab the wheel at opposite ends and shake it up and down. When doing this, pay special attention to where you put your hands. Always place your hand at 6 and 12. If you can feel the wheel being loose, look behind the bearing and make sure you can actually see the bearing move. A loose ball joint can also cause the same condition so make sure to rule that out. If you can’t really see the bearing that well, ask someone else to shake the wheel for you, place a finger between the inner and outer race, and see if you can feel it move. If there’s any play between both races, the bearing needs to be replaced, and that, even it doesn’t make any unusual grinding noise.
On the other hand, play in the wheel when placing your hands at 3 and 9, and shaking it from left to right may indicate a loose tie rod or tie rod end problem instead.
How long can I drive on a bad wheel bearing?
A bad wheel bearing, especially in its initial phases, will not put your car out of action straight away. Still, that doesn’t mean you should ignore it and drive around as if everything’s fine. A humming noise coming from the bearing results from excessive wear, which increases friction and causes high temperatures. This means that if you go on a lengthy journey with a bad bearing, it might seize up. However, your car might be good for shorter trips at lower speeds until you change the bearing.
On the other hand, wheel bearings with any amount of play are far more dangerous as they can fall apart. This is because wheel bearings are the only component that connects the wheels to the rest of your car. And even if it stays in one piece, excessive play inside the bearing will upset the steering and handling characteristics. To avoid any damage or potential hazards, replace the wheel bearing as soon as you notice any of these symptoms.
How much does it cost to replace a wheel bearing?
Despite slight differences according to the make and model of the car, wheel bearings come in two main types. The majority of older cars have a wheel hub with the bearing inside, making it possible to replace only the bearing. While the bearing itself is not expensive, the removal process requires the brake components to be removed.
Modern cars use a special wheel hub, which integrates the bearing, rim flange, and ABS ring into one assembly. Being a sealed and non-serviceable component, the only thing you can do is replace the entire unit. Although wheel hubs cost several times more than single bearings, the removal is much easier. On the other hand, bearing assemblies also come in two types: bolted or pressed in place. While bolted models are quite simple to replace, removing and reinserting pressed ones require a hydraulic press. In that case, it’s often better to just bring the car to a trustworthy mechanic.
On most vehicles, replacing a wheel bearing takes about an hour but that obviously depends on the car model. As a general rule, you can expect to pay about $400 for a wheel bearing replacement. The labor will be anywhere from $140-$180, while parts may cost as little as $200 or as much as $400.
OEM bearing usually cost more than aftermarket models. If you have a really tight budget, you might try to find a used wheel bearing from a local junkyard. It’s not uncommon for junkyards to receive recent vehicles with low mileage but damaged the point of no repair. If you are lucky enough, you might find a crashed car with good bearings for a fraction of the price of aftermarket ones.
Wheel bearings are one of the important components that keep your car rolling smoothly and effortlessly. As they are reliable and require no maintenance, most car owners don’t think much about them. However, if there is a humming or grinding noise while driving, your car might have a bad wheel bearing. Although this will not put your car out of action straight away, you shouldn’t ignore it. Your best bet to keep the repair cost as low as possible is to have your car inspected and fixed as soon as you first notice bad wheel bearing symptoms. When in doubt, look for the right troubleshooting and replacement procedure found in your car’s repair manual. Always remember that following the manufacturer’s recommended procedure is always the safest way to go.