How can you tell if wheel bearings are going bad? - Page 2 - PeachParts Mercedes-Benz Forum

barry123400 · #16 01-25-2008, 02:03 AM

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.

bobs · #17 01-25-2008, 04:08 AM

Quote:

Originally Posted by chupr98

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!

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.

bobs · #18 01-27-2008, 06:57 AM

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?

Kestas · #19 01-27-2008, 11:06 AM

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.

bobs · #20 01-27-2008, 12:09 PM

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?

Hatterasguy · #21 01-27-2008, 01:26 PM

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.

bobs · #22 01-27-2008, 05:31 PM

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.

Kestas · #23 01-27-2008, 10:33 PM

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

bobs · #24 01-28-2008, 06:10 PM

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!

Hatterasguy · #25 01-28-2008, 11:57 PM

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.

bobs · #26 02-07-2008, 04:13 AM

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.

bobs · #27 02-09-2008, 07:25 PM

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!

Larry Delor · #28 02-09-2008, 09:25 PM

Can you post a picture?

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

bobs · #29 02-10-2008, 10:44 AM

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!

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.

This is bad, right?

Kestas · #30 02-10-2008, 11:52 AM

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.