Left Front Humming Noise After Pothole?

Hello people that are smarter than me (and smarter than the Mazda techs).

My wife hit a large pothole the other day and now we are hearing a humming noise from the left front, and a slight vibration through the steering wheel. The dealer told just balancing and rotating the tires would fix it, which it predictably did not. To me it sounds like a wheel bearing, but I am not a mechanic, nor did I stay at a Holiday Inn Express last night.

Could a pothole cause a wheel bearing to go bad? I pulled the offending wheel off and didn't see any bends or flat spots. It also doesn't feel like the vibration you would get from a bent wheel. Any other suggestions on things to look at? The noise seems to be getting worse since it happened.

The car is a 2015 Mazda 3 sedan.

From those symptoms it could've been a wheel balance problem (caused by wheel damage) although the humming should've been a suggestion that it wasn't. So yeah it's likely a damaged wheel bearing or hub.

The only other possibilities are axle or CV damage, but the fact that it started after hitting a pothole suggests bearing/hub.

Potholes can absolutely kill a wheel bearing due to impact damage to either the balls / rollers or the bearing race.  That's probably what happened.  

Wheel bearing was my first thought.

Is it normal for the bearing to be damaged and not the wheel? I have flat spotted wheels before, but never had the hub or bearing damaged.

Devilsolsi said:

Is it normal for the bearing to be damaged and not the wheel? I have flat spotted wheels before, but never had the hub or bearing damaged.

Depends on the car as far as how strong the wheels are and how tough the bearings are.  Usually the wheels will give first, but not always.  FWIW, based on a few people I've talked to, having a front wheel bearing get noisy after a pothole impact seems common on the 2nd gen Prius.  

It happens. If bearings didn't get damaged more easily than wheels, we'd be changing wheels more often than bearings!

Wheel damage is usually caused by tire underinflation (or sudden loss of pressure due to the same impact that bent the wheel) or pressure being sharply focused on one part of the wheel. It's entirely possible for the wheel to remain pristine while the bearing gets beat to death.

Based on your description it must be the hub bearing or CV joint. 

Automakers design/engineer cars where the wheel is designed to not fail before any of the normal suspension failure points. Bearings, tie rods, axles(CVJs)  were deemed to be basic failure locations. So it is very common for the tire and wheel to be fine but a hub bearing, axle component, or suspension joint failure to occur. Theoretically any failure should still allow you to guide the car to the side of the road.

I just replaced my front and rear bearings on the right side of my car just for this type of impact.

The dealer should know this and should fix it. Heck all of the responders to your post haven't even heard or seen the car and we all agree on the failure point. 

After a quick search I see that the front hubs are about $150 each they are a full assembly of studded hub with bearing and housing. These type are very easy (no press or exotic tools) to replace given no rust. You could do it with rented slide hammer and adapter tools from your local auto parts stores. Very large socket to fit the axle nut, new cotter pin, breaker bar, torque wrench with high-ish torque setting. 

Impact wrench to get things apart.

As it was a road damage incident I doubt it is covered under warranty. 

I assume you looked at all the joints already for torn lower control arm bushings etc. If after the hub replacement, you still have an issue then maybe the inner or outer tie rods have failed. I have had three inner tie rods fail on my rallycross car. They are a pain so I hope you just have a bearing to swap. 

The humming does point to a wheel bearing but the vibration points to a damaged tire and or wheel.  If I where a betting man I'd place my wager on it being all three.

I think you need a different repair shop.  Also, check with your insurance company.  That's not a warranty repair but it might be covered by your insurance.

Is "Brinelled" the word?  

A hum, especially one that changes pitch or volume as you turn the steering wheel to load and unload the hub is almost always a bearing.  A cupped edge of a tire can fool you, but they are generally different on changing road surfaces.

APEowner said:

The humming does point to a wheel bearing but the vibration points to a damaged tire and or wheel.  If I where a betting man I'd place my wager on it being all three.

I think you need a different repair shop.  Also, check with your insurance company.  That's not a warranty repair but it might be covered by your insurance.

We had them rotate and balance the tires. The only noise or vibration remains in the left front. It also isn't a vibration like what I have felt when a wheel has been bent, out of balance or a tire issue. Kinda hard to describe. I am not going to go through insurance for something this minor. We have had a couple other claims in the past few years so I would prefer to take care of this myself.

Streetwiseguy said:

Is "Brinelled" the word?  

A hum, especially one that changes pitch or volume as you turn the steering wheel to load and unload the hub is almost always a bearing.  A cupped edge of a tire can fool you, but they are generally different on changing road surfaces.

Yeah it also seemed to be louder when their was load on the left front as well.

Devilsolsi said:

APEowner said:

The humming does point to a wheel bearing but the vibration points to a damaged tire and or wheel.  If I where a betting man I'd place my wager on it being all three.

I think you need a different repair shop.  Also, check with your insurance company.  That's not a warranty repair but it might be covered by your insurance.

We had them rotate and balance the tires. The only noise or vibration remains in the left front. It also isn't a vibration like what I have felt when a wheel has been bent, out of balance or a tire issue. Kinda hard to describe. I am not going to go through insurance for something this minor. We have had a couple other claims in the past few years so I would prefer to take care of this myself.

Ah, I didn't realize that you'd had the tires rotated and balanced.  That would rule them out.  It still sounds like the wheel bearing is bad.  Is the vibration fairly high frequency, as if you were feeling the hum through the steering wheel?

APEowner said:

Devilsolsi said:

APEowner said:

The humming does point to a wheel bearing but the vibration points to a damaged tire and or wheel.  If I where a betting man I'd place my wager on it being all three.

I think you need a different repair shop.  Also, check with your insurance company.  That's not a warranty repair but it might be covered by your insurance.

We had them rotate and balance the tires. The only noise or vibration remains in the left front. It also isn't a vibration like what I have felt when a wheel has been bent, out of balance or a tire issue. Kinda hard to describe. I am not going to go through insurance for something this minor. We have had a couple other claims in the past few years so I would prefer to take care of this myself.

Ah, I didn't realize that you'd had the tires rotated and balanced.  That would rule them out.  It still sounds like the wheel bearing is bad.  Is the vibration fairly high frequency, as if you were feeling the hum through the steering wheel?

Yes exactly. You can hear the hum and feel it. Very different than vibration from a bent wheel.

That's a wheel bearing.  I'd replace it very soon.  If it fails catastrophically the brake rotor will flop around inside the caliper and push the brake pads back.  When that happens it takes several rapid pumps of the brake pedal before the pads can square up the rotor and the brakes will actually stop the car.  It's quite disconcerting and on some cars it can take out the ABS sensor.

Jack up the car, use safety stands under it.  Start the car and put it into gear. 

Without getting tangled up in the spinning wheel see if you can locate the source of the noise.   You can also put the end of a length of steel tubing onto various static places and see if you feel increasing vibration the closer you get to the suspected rotating part. 

If its not limited slip you can block one wheel from spinning and then the other.   

Do this by placing the block at the wheel you want to stop before you engage the transmission. 

And be cautious if you do this, you don't want to be in a position where a flying block can hit anyone.  

Sometimes having ears and eyes on a noise can help pinpoint it.

But the symptoms do point towards it being bearing or CV related. 

APEowner said:

That's a wheel bearing.  I'd replace it very soon.  If it fails catastrophically the brake rotor will flop around inside the caliper and push the brake pads back.  When that happens it takes several rapid pumps of the brake pedal before the pads can square up the rotor and the brakes will actually stop the car.  It's quite disconcerting and on some cars it can take out the ABS sensor.

Thanks. Going to do some research today to see if this is something I am comfortable tackling myself, or if it is just going back to Mazda.

Ok. Replaced the hub/wheel bearing over the weekend. The noise and vibration is greatly reduced, but still present. Same tone, same characteristics, just less of it.

Could there be something else that got damaged at the same time with the same symptoms?

Well the wheel has been balanced so it's not a balance problem...could the structure of the tire have been damaged? It could be balanced and still vibrate when actually driven on if it's damaged. Could you run a spare on that corner for a test?

Edit: From your original post it seems that the tires have been rotated as well...if so, the next most likely culprit is the CV joint. Roll down your windows and make slow, tight turns in a parking lot. Do you hear clicking/crunching noises coming from the front that match wheel speed?

In reply to Devilsolsi :

If you had bad luck like me. Your front wheel bearing and rear wheel bearing were both taken out by the initial event. If the steering wheel vibration is gone then most likely the rear wheel bearing. 

Conversely if the vibration is reduced but the steering wheel is vibrating just as much. Then I would look for a suspension link failing:

1. tie rod inner or outer
2. Control arm link/bushing/balljoint may have failed
3. Upper damper mount
4. CV joint.

I had a similar instance a while back. The alignment got knocked off just enough and it needed a tie rod. Rare instances a toe in/toe out problem gets the tire humming. Always a good idea to check ALL your steering and suspension pivot points and do an alignment.

GameboyRMH said:

Well the wheel has been balanced so it's not a balance problem...could the structure of the tire have been damaged? It could be balanced and still vibrate when actually driven on if it's damaged. Could you run a spare on that corner for a test?

Edit: From your original post it seems that the tires have been rotated as well...if so, the next most likely culprit is the CV joint. Roll down your windows and make slow, tight turns in a parking lot. Do you hear clicking/crunching noises coming from the front that match wheel speed?

Neither of us have noticed any clicking or crunching. Just the sorta humming noise at speed. Will give your test a try this weekend anyway though just to see if I hear anything.

Advan046 said:

In reply to Devilsolsi :

If you had bad luck like me. Your front wheel bearing and rear wheel bearing were both taken out by the initial event. If the steering wheel vibration is gone then most likely the rear wheel bearing. 

Conversely if the vibration is reduced but the steering wheel is vibrating just as much. Then I would look for a suspension link failing:

1. tie rod inner or outer
2. Control arm link/bushing/balljoint may have failed
3. Upper damper mount
4. CV joint.

The sound is definitely coming from the left front so I feel comfortable ruling out the rear hub/wheel bearing. What would be the best way to check the other suspension pieces you mention? I don't want to start replacing parts just to replace parts.

ncjay said:

I had a similar instance a while back. The alignment got knocked off just enough and it needed a tie rod. Rare instances a toe in/toe out problem gets the tire humming. Always a good idea to check ALL your steering and suspension pivot points and do an alignment.

 

Hmm that is an interesting thought. At the very least I will drive it and see if pulls at all to either side. An alignment probably isn't a terrible idea at this point anyway. Last year she hit a pot hole hard enough to flat spot a wheel on the other side.