Car problem - Intermittent vibration

Hi all

This is a copy of something I posted on the CarTalk forums. Unfortunately it hasn’t attracted any replies there so I’m hoping there might be some car experts here or maybe someone can suggest a good auto repair forum.

I’d appreciate any suggestions about this. I have a Hyundai Sonata 2005, 4 cylinder manual. It’s done almost 94000 miles which means there’s about 6000 left on the extended warranty.

It has an intermittent vibration problem that is related to road speed / wheel rotation. It’s not related to engine speed. I’m driving along and things are good until it starts. It’s slight at first but progressively gets worse over the next minute or so. It’s an up and down vibration. If I didn’t know I’d swear that one of the wheels is not round or the road is very corrugated. It gets so bad that I pull over and stop. It doesn’t feel safe and I fear doing some damage. If I wait a minute and move off again then it has usually gone until next time. When it’s at its worst when I’m stopping I can feel the vibration in the brake pedal and I think the car is going up and down slightly for each wheel rotation. It’s hard to tell if it’s coming from the front or back. I don’t know if it’s related but sometimes I hear a single “clonk” noise coming from the back as I start off slowly. It hasn’t happened often enough to be sure but I get the feeling that if I hear that then there is a greater chance of the vibration problem happening somewhere at speed during that trip.

I have taken it to the dealer. They did a brake job on it a few weeks ago. I think they did an okay job. The brakes are working fine now where there was vibration in the pedal and the steering during braking before. This other problem was happening before the brakes got bad so I don’t think it’s related although it was hard to tell earlier because, while braking at least, because it was difficult to separate the brake vibration with the other problem.

The dealer now tells me that tires are the problem. They were wearing slightly unevenly or something. However, I don’t think they have really experienced the bad problem. When driving along “normally” there is a little bit of unevenness in the road noise and feel. I think that is what they have noticed and think that is what I am talking about but it’s NOTHING compared to the bigger problem when it occurs. Could a tire cause a problem that gets really bad and goes away again? I doubt it but I’m no expert.

I’m thinking of taking it to a local repair place who have done work for me on another car and have a pretty good reputation. I’ll have to pay them to try to find out what it is and then if it’s something that the warranty covers I’ll take it back to the dealer. I don’t know what else to do. I’d really like to catch it before it’s too late if the warranty would cover it which it should if it not normal wear and tear.

Thanks for any ideas …

See if you can get a dealer service person to ride with you while you show them the symptom. This will be more of a challenge if it doesn’t occur consistently at a given speed (or speed range), takes a long time to present itself, or requires a longish drive to reach a suitable roadway. For noises and vibrations, it’s not uncommon for the servicer to detect something that turns out not to be what the customer was concerned about, and being able to definitively say “There it is! Do you feel/hear it?” is a big plus.

Tires may be a factor. Harmonic vibrations in an out-of-balance wheel/tire assembly are speed related. However, the symptom you describe is not typical of an unbalanced wheel alone, so I suspect something else is faulty, either instead of or in addition to a tire flaw.

If you can’t get the dealer to agree to the ride-along, or the symptom doesn’t occur then, your plan to have another shop evaluate it is probably the best option.

I am certainly not an auto repair person, but a coworker was having the same vibration problem that you describe, but on a Ford Mustang. After much investigation, it was finally decided that it might be the torque converter.

I’d be curious to know what you discover so that I can mention it to my coworker.

“. . .sometimes I hear a single “clonk” noise coming from the back . . .”


Manual transmissions do not have torque converters.

I had a similar problem once that went away as soon as I had all the tires rebalanced.

Thanks for the replies. U-Joints sounds like a good possibility to me. I think the clonk noise is always when I start moving forward after backing out which would suggest something flexing when the direction of force changes. I’m not sure quite how that would cause an up and down vibration with the wheels turning but I guess if something related to the wheels gets out of alignment then bad things can happen. I seems like something is loose enough so that it slips back into place for a while.

I think I’m going to call the service manager at the dealer and give him one more chance to look at it before I take it somewhere else. I may not have impressed on them quite how bad it is. Unfortunately taking someone for a drive probably wouldn’t help because it sometimes goes for days without a problem. It didn’t happen today.

And front-wheel drive cars don’t have u-joints.

Thanks, I wondered about that.

Tire, wheel bearing, CV joint, … That’s what I got so far. 94K is quite a bit on original equipment.

Yes, this happens all the time. When the car is parked overnight, the part of the tire that touches the ground becomes flat. Then, when you start the car in the morning the tires retain that flat spot and that can cause vibrations similar to those when the wheel is out of balance.

But as the tires warm up during driving, they regain their round shape and the vibrations go away. It should need no more than 5-10 minutes of highway driving for the vibration to stop. All tires exhibit this behaviour, but it is more pronounced on some brands/models than others.

Now you mentioned in the OP that the vibration was so bad that you had to stop the car and check. This isn’t normal, either there’s something really wrong with the tires or there’s some other problem. Anyway, if you still have the factory tires it would be a good idea to change them. Hyundai ships their cars with really shitty tires (usually Hankook or Kumho). I would suggest to use some better brand, like Bridgestone, Michelin, Pirelli, Continental, etc.
Tire shop owner

If the car seriously shakes then you may have a bad wheel bearing and you’re hitting the resonate frequency. This will happen very quickly if this is the case. It will go from just noticeable to violently shaking in seconds. Had this happen years ago. The car would shake at a certain exhaust note so basically it occurred in each gear.

If you broke a cord in the tire you may be able to feel it by jacking the car up and spinning the tire. Sometimes it’s visually obvious with a bulge or the tire looks “wobbly” because the tread has shifted.

If the CV joint is bad you might look for signs such as a ruptured boot to see if it has lost grease or been contaminated by road grit.

Upon rereading your post I wonder if you have rear drum brakes and they are loose. I’ve had drum brakes become so loose they clunked. The test and fix for this is to back up and repeatedly pump the brakes which will activate the adjustment wheel. do it 10 or 20 times and see what happens.

The problem does not happen when I drive off from cold. It can start happening at any random time while driving at highway speeds.

No it’s not the factory tires. This is at least my second set of replacement tires since new. These ones are not real expensive but the Hyundai dealer put them on.

Yeah I understand a bit about resonate frequency etc. It seems like that when the problem starts but wouldn’t I then expect the vibration to change when I slowed down? Once it starts, the amplitude of the vibration doesn’t seem to reduce until I completely stop. Even when I’m about to stop and crawling along at walking speed, it’s still there just as bad, but at a lower frequency proportional to speed.

I just made contact with my brother who is an auto mechanic in New Zealand and he thinks it’s the inner CV joint.

I’m pretty sure it’s disk brakes all round.

I’m not going to say it’s impossible, but this strikes me as highly unlikely for two reasons. One is that inner CV joints work through a much smaller arc (amount of flex) than outer ones, and very rarely develop problems. The other is that given the symptom maintains even at very low road speeds, I can’t envision a reason why a glitch in the joint would reset itself simply from sitting still.

Of course that last aspect, the resetting, is rather unusual and it’s a bit of a stretch to imagine the scenario where that would apply to anything. I’m thinking it must relate to something that can migrate in and out of its normal position. I have seen that happen with a wheel bearing. Perhaps when it has stopped moving and the forces acting on it change it’s in a position to slip back into place.

The combination of intermittance and resetting when stopped presents quite a challenge in detecting the cause of the problem. Some thinking outside the box may be helpful, but I suspect it will come down to plain old luck in someone looking at the right thing at the right time.

I think you’re right because it happened again tonight and I’m now pretty sure that it’s in the back so I guess that eliminates CV joints. The other noise definitely comes from the back too. It actually sounds more like a “snap” than a “clonk” just as I’m starting off. I’m now guessing the wheel bearing, not that I know anything but there really isn’t much else in the back that rotates is there? It doesn’t seem to be related to brakes. I can hit the brakes while it’s happening and it doesn’t change the sound at all other than slowing down as the car slows.

OK, I have to say it:
When I first saw the title, I thought it said “Cat problem - Intermittent vibration”, and my first thought was “I didn’t know that purring was a problem.”

In this case would it not make sense to first have an alignment check and tires balanced (and replaced if old)? The alignment and balancing are cheap, easy, and quick and problems in those areas could possibly be aggravating the situation, even if not the per se cause. It would certainly help focus troubleshooting once those potentials were eliminated.

Something in the rear suspension is at play here. Under different loads and conditions the suspension is reacting differently and even harmonizing under certain conditions. The clunk is something loose, and the something loose is later allowing play and vibration.

Get the rear suspension checked out thoroughly.

Secondary glance to the exhaust, to make sure it hasn’t sagged onto the rear suspension.

Holy shit! Sounds like the wheel lug nuts are loose. Check them ASAP!!!

Thanks for the replies. It’s booked in at the dealer first thing Monday. I don’t think I’ll drive it until then because I’ve just noticed a few scary things. The back wheel where I’ve been hearing the noises is unmistakably hot after driving and it’s leaking what I assume to be brake fluid. I guess that’s good news because it should be easy to find the problem. I wonder how safe it is to even drive there but I checked the brake fluid container in the front and it’s full so it can’t be leaking much. It doesn’t feel like the brakes are locking on or anything. I guess I’ll find out on Monday.