How can you tell if wheel bearings are going bad?
 

This is kind of a general question about wheel bearings on my newly-purchased '97 S420 with 85k miles on it. The car rides just fine, although it needs shocks. What had me puzzled though is a slight rumble I feel through the steering wheel at highway speed. The only thing I can think of would be the wheel bearings going bad. Can anyone confirm/debunk this?

So far I have replaced the steering damper (it was leaking anyway), and had the (almost new) tires re-balanced. These two thing cleaned-up the front end's behavior quite a bit but I'm still trying to pinpoint the source of the rumble. My '97 S320 is smooth as glass in comparison. I'd appreciate any thoughts.

Jack up the front end.
Spin each front tire slowly ( listening for grinding/scraping sounds ).
Grab the wheel & wiggle it up/down, sideways, in & out.
That should tell you something.;)

Good point! So if it wiggles or makes grindy noises, that's not good, right? :eek:

That's right.
And I wouldn't drive it too far. ;)

Just to possibly save time.... After a bit of a drive, feel the area closest to the hub. If one wheel feels warmer than the other, check the warmer one first. (friction causes heat)

inspect the tread of the tires.
Tears and cuts on the tread an cause vibrations.

I handle the technical end of warranty claims for wheel bearings in our company. I've seen hundreds of customer and dealer narratives relating to bad bearings. The common complaints customers have when a bearing goes bad is that they hear a noise that is described as grinding, roaring, whining at 30 mph to highway speeds. I've never heard a customer describe a valid complaint as noise coming through the steering wheel. So I say look elsewhere for your noise, perhaps in the tires as oceanview suggested.

I've personally only experienced a bad bearing once while diagnosing a colleague's car. The noise was unmistakable and could easily give someone a migraine. The cause was a 2 mm spall on the race and the wheel was tight. If you find looseness when manhandling the wheel during your check, then the damage is far advanced and you should have heard noise long time ago.

Thanks for the info! From what you say then its probably not bearing-related. On the way in to work this morning I did a little experimentation and found that it goes from a slight rumble at 60mph to a definite shake (almost like an un-balanced tire) at 75-80. Like I said earlier, I just replaced the steering damper, had the tires re-balanced, and adjusted pressure to 27psi both front and rear. I guess its time to start looking at steering linkage and maybe have an alignment done.

Out of balance tires usually are the worst @ 60 - 70 mph.
It's not uncommon to have a tire vibration " go away " at higher speeds. ;)

I have had similar experiences on different vehicles. Almost always it has been the tires. Tires can have defects that cause out of roundness and density differences that feel exactly like and unbalanced wheel. I usually buy cheap tires and I have the problem often. The only solution is to swap out the tire that is rough. Shaving, balancing, rebalancing, nothing will fix a tire that is not uniform in density or composition. Never had a rough tire with Michelin.

Mark

Funny, because that's what is on the car. Michelin MXV4's

I had these same sort of symptoms on my 85 300D.
I had just replaced the engine, and soon after I started to feel more than
hear, something rough in the steering wheel and fuel peddle.
this was over the course of 3000 miles.
at first I thought, what`s wrong with the new eng? as time went on felt like gear noise, or roughness. the towards the end like snow tire type noise, but now loud.
changed the L/F tire, no change. finally pulled the hub and the inner bearing cage was starting to deform. replaced the bearings and races and
smooth as butter now. both hubs never felt hot.

Charlie

Were both hubs bad? Did you replace the grounding strap after replacing the engine? If the grounding strap is omitted, the engine will try to ground itself through the wheel bearings, and the bearings will destroy themselves in short order. So will the next pair.

I just replaced both bearings, what I can tell you is my bad bearing sounded like subway train on railway track at high speed! No words can explain!:confused:

Engine mounts? Flex joints?

Move the front wheels to the back and vice versa before procceeding any further. If you do it yourself it costs nothing.
Identical situation still there then proceed. Also have a look at any wear pattern if present on those front tires.

That's kind of what worries me. I can hear it go "thrum-thrum-thrum" when I go down the highway. It almost sounds like a twin engine aircraft's exhaust note, but the sound changes with road speed and not engine speed.

I think I have a bushing going bad back there as well. I can hear a faint "thunk" noise when going over bumps at parking lot speeds.

OK, I just did a quick test. I jacked up the front of the car, grabbed the wheel at the top and bottom, and gave it a good wiggle. I can feel some play (maybe 1mm or so) at the edge of the wheel. That's bad, isn't it?

Everything I know tells me that the bearings need to be adjusted at the very least. But since I don't know the mileage on them I'm probably looking at replacing both bearings & races.

Am I totally off base here or do I need to give Phil a call on Monday?

You're a bit off base. I can categorically tell you that bearings - once properly installed - never need to be adjusted. Bearings don't wear in the traditional sense, nor do they ever need adjustment. I'm not sure where you get that information.

With proper care, wheel bearings should last the life of the car. When I say proper care, I mean change the seals and grease at least every 60-90K. Most bearing failures occur because of improper mounting - not from wear.

About that wiggle you discovered... you have to narrow down where it's coming from. It could be from the ball joint.

With 85K, I'd say it's time to do the bearing maintenance. At that time you can inspect the bearings for spalling or imperfections to see if they are suitable for continued use.

The operative words here are "properly installed" and "proper care". :) From what I can tell, the PO did little more than have the fluids changed regularly and have stuff replaced that broke. The pads & rotors look fairly new so my guess is that someone has been in there not too terribly long ago.

What troubles me is that the trail of maintenance receipts has moved from dealers, to indy MB shops, to "Joe's Garage", so I have reason to suspect the quality of any work done to it recently.

I'm definitely going to pull the hubs off and at least inspect the bearings.

Kestas, what's your recommended method for determining if the bearings/races are still serviceable? Other than the obvious visual inspection, are there any other tests I should do?

I'd check out the lower control arm bushings. Vibrations on the highway can be many things but on a W140 that would be a good place to start.


Its not the wheel bearings you would hear them, and considering how long this has been going on probably would have seized by now.

Good point. I'm going to re-pack the bearings & inspect all the front suspension components when I put my shocks on later this week. I'll keep you posted.

It's essentially a visual inspection. When you inspect the bearings, they should still have much of the original hone/grind finish marks on the running surface. They should be discarded if you find any of the following:
- cracks
- spalls
- chatter marks
- excessive nicks or dent marks
- discoloration (beyond very faint straw color)
- corrosion
- gray matte finish

Update: I replaced the front shocks this evening, and I think the prize goes to Hatterasguy & kestas.: Once I got the wheels off, the bearings felt fine, but the lower control arm bushings looked suspect. While they weren't totally shot, they definitely showed wear and some cracking.

I didn't get a chance to properly inspect/repack the bearings due to time constraints, but I'm pretty sure I've got some miles left before I have to do them.

The shock replacement was ridiculously easy and made a HUGE difference in ride quality. I think I'm going to do the rears next payday.

I still have the hum/thrum when I drive at freeway speed but its no longer buzzing the steering wheel like before. I'm becoming more convinced that it has to do with the POS Michelin tires the PO had installed. I see a set of Contis coming my way in the not too distant future.

Thanks again for everyone's help and input. This forum is the best!

I think the LCA bushings are a bit of a job on the W140. I have looked at them but never changed them, looks a bit more involved then on my W126.

Update: I replaced the rear shocks and put a new set of Continental ContiPro Contact 235/60 HR16s on the back. The car now rides like it should and it nice and quiet. I still hear a very slight "thrum" noise but I now attribute this to the Michelins I still have on the front. They're in decent shape tread-wise but I think I'll replace those with Conti's as time/finances permit just to keep everything matched.

Update #2: I pulled the front wheels today to get a better look at the front suspension. My lower control arm bushings are looking kind of rough. They're dry and cracked, but look like they're all there. Is it time to replace them?

I also did another shake test on the front wheel and found a slight bit of play both in the vertical and horizontal directions.

I pulled the caps on the wheel bearings, and they both looked real clean, almost like someone just did them. I have a question on the amount on grease in there though. It's kind of a bright green grease, almost the color of Prestone, and it's barely covering the bearing. The bearing retainer and the inside of the dust cap are completely dry. This does not sound right to me!

Could someone please verify how much grease I should see. Thanks!

Can you post a picture?

You don't need gobs of grease - too much isn't good either.

Done. The first one, pict1554.jpg is the bearing. One thing I noticed is that the grease has almost a waxy consistency to it. It's not the typical long grain grease I'm used to seeing packed in wheel bearings.

Since I had the wheel off, I thought I'd share a few more with you! :D

The second one, pict1557.jpg is the sway bar bushing. This seems to be in pretty good shape, don't you agree?

Next, is pic1558.jpg. This is the front LCA bushing. My guess here is that it probably needs replacing.

Finally, pict1664.jpg is the rear LCA bushing. :eek: This is bad, right?

It's a good sign when you can see the original color of the grease. The photo doesn't indicate anything wrong with the bearing or grease. I'm not sure about the "waxiness" you describe. That's a judgemental observation.

I can't tell about the sway bar bushing. That is best determined by testing the slop with a crow bar.
The front lower control arm bushing is on its way south.
The rear lower control arm bushing needs to be replaced.
Those are excellent pictures btw.

Coming from you, I'll take it that the bearings were done properly. :)

Thank you. I shot them with a Vivitar 8.1 MP camera set in macro mode. I was surprised at their quality as well. You ought to see them at full resolution. They're pretty impressive.

If In Doubt Pull The Wheel!!!
 

I have been a mechanic all my life and I have worked on everything from fancy cars to big class 8 road trucks and everything in between, when someone asked how do you tell if a wheel bearing is going bad, I think of all the thousands of wheel bearings and races I have installed over the many years of working on vechicles. If your going down the hwyway and you hear a rumble and you feel shaking in the steering wheel and then you see your wheel pass you by you have a bad wheel bearing, Don't laugh at this, IT DOES HAPPEN. But it doesn't have to happen, now my next question is why do most people like these forums, most people read to learn, and and there is no such thing as a stupid question, My reason is I have been a mechanic all my life and there isn't a day that goes by that I don't learn something new, somebody always has a better way to do something. THE ONLY WAY TO CHECK A WHEEL BEARING IS TO REMOVE THE WHEEL AND REMOVE THE HUB AND THE REMOVE HUB SEAL AND THEN REMOVE THE BEARINGS AND WASH THEM IN A PARTS CLEANER AND VISUALY CHECK THE BEARINGS FOR WEAR, if they are worn you will see pits and discoloration on races and bearing rollers, now after inspecting the bearings you find nothing wrong you do need to repack the bearings properly if you don't know how to do this then I suggest you buy a bearing packer or learn to do it with the palm of your hand, there is a right way and a wrong way. Now if I had 85.000 miles on my car I would just invest in brand new wheel bearings they come with races and are fairly . cheap. so if you want to learn do it yourself if not take it to a shop it.s called Maintenance. Jerry, Master Certified ASE Mechanic

Jerry, If you'll look at the pictures I posted, you'll notice that it looks like the bearings have been freshly done. The wheel turns smoothly, and the free play I described appears to be caused by the bad lower control arm bushings, not the bearings.

As a former aerospace mechanic with 12 years of experience, I also know a little bit about "maintenance." Quit being so angry. Sheesh....:rolleyes:

Nice pictures.

The bearing looks ok - since it is exposed, I would probably clean and repack it, if I had the grease on hand. (but if I didn't, I wouldn't be worried about it).
That rear bushing sure does look rotten.
I don't know how much of a PITA the sway bar bushing would be, but if it doesn't look terribly difficult, I would get new ones. If does does look like a pita, then I would wait to replace them, along with other parts that will be replaced in the future.

Well looks like I was right.:D;) Those wheel beearings look fine, if you are really picky like me repack them, or just leave them alone. That grease looks like new.

However those LCA bushings need replacement. Typical W140 problem, first thing I checked when I went W140 shopping with my friend a couple years ago.

Everything I have read says they are a real pain to replace. For anyone who as done it, would you do it again if you had to? (Want to stop by and give me a hand?:D) Also, while I'm in there I may as well do sway bar bushings & links too, right?

Finally, looking at pricing from Phil's online store I find this:

Sway Bar bushing kit: 2ea @ $114.66
Tool required to replace them (eBay): $199.00
TOTAL $428.32

OR


Entire lower control Arms 2ea @ $261.20
(includes bushings already installed)
TOTAL $522.40



For $100 more I get two brand new lower control arms as well! I'm kind of leaning towards the second option....