DIY Wheel Bearings (W126) - PeachParts Mercedes-Benz Forum

#1 06-16-2002, 07:28 PM

My buddy and I are going to do a brake job on the 560SEL in about a month. Pads, front rotors, brake hoses, ABS sensors etc.

I was told that I might as well replace the wheel bearings as well, but recently read some posts that if you're not sure what you're doing -- leave it to the experts.

My buddy has done bearings (not MBs) and is a competent DIY'er in general. Would I still be foolish to tackle this ourselves? From what I understand I'll need a dial gauge to set preload, but also that many people do it by backing off the axle nut a set amount or by feel. Off hand, what does the gauge need to be set to for the W126? Didn't see it in on the service CD (at least not yet).

Thanks for any advice or info!

Mike Murrell · #2 06-16-2002, 08:35 PM

Benzmac reported a good ways back that the rule is "zero preload-zero play". I take that to mean the hub can be turned without pulling a fish scale off of 0 and that there's no play when pushing-pulling from 12 o'clock and 6 o'clock.

If you feel you need a dial indicator to get this, then buy one. I've done it without one and have continued to live for quite sometime. There's no question that faulty wheel bearing work can put one in the grave, but this can happen on ANY car; not just an MB.

What I'm talking about in my opinion applies to the front end. I'm not sure if you really need a dial gauge for the rear.

If you're not experienced in wheel bearing repack and the subseq. installation of the bearings, you might want to find something besides a 126 to cut your teeth on. If your pal is well-versed, go for it, but do so at your own risk.

MikeTangas · #3 06-17-2002, 01:42 AM

is what you seek Ted. Looks like the dial indicator need to be set to 2mm. Slightly different check than what is called for on the 4.5 (which measures the amount of force required to turn the hub).

To paraphrase the manual:

Tighten the clamping nut, while rotating the hub, to the extent the hub will be hard to turn. Then slacken the clamping nut by approximately 1/3 of a turn, and release tension by whacking the spindle with a plastic mallet.

Personally, I have never used any sort of gauge to set wheel bearings, other than the gauge of what I feel while rotating the hub. I must have been doing something right, because I've never lost a wheel bearing.

#4 06-17-2002, 03:42 AM

I am a pretty fair diyr and I couldnt get em right after two tries, 1 with a feeler guage, the other with the previous "backoff" method listed. Both times, bearings made low humming noise drove me nuts! 2 possibilities, either they have to meticulously "perfect" (dial guage required?)or #2, I had defective wheel bearings, not sure which? I ended up taking it into the shop and 353$ later, problem solved. I thought I paid a little much, the bearings cost them 101$, they marked it up 38%.. then they charged me 3 hours labor, i know it did NOT take them that long..Ok, I am typical diyr complaining of fee's I know..

stevebfl · #5 06-17-2002, 08:31 AM

Front wheel bearings on many MBs including the 126 body are the same type as Chevrolets.

One of my first lessons in finance/selling parts came with wheel bearings. In the case of 126 bodies these are, by standard, "Set3" and "Set5" front wheel bearings. After leaving the MB dealer I found I could buy $30 MB bearings for 15 from the local parts store and I marked them up 65% and sold them for 24.75, giving my customer a break. After about a year I found out about Direct Importers and found I could now buy the bearing for $4 from the exact manufacturer as from the MB dealer. Now I am faced with the moral dilemma: do I keep my same mark-up at 65% and sell the product for $6.60 and reduce my per part profit from $9.75 to 2.60.

My shop pays out $14,000 in labor expenses every week. We average about 14,500 labor billed a week. We pay our bills out of parts profit. I still sell that bearing considerable less than MB would and now know where to buy the exact bearing to make unconscienctiousable profit.

As to the adjustment. Mike has the concept, just a little less tight than too tight (bg). My German partner always showed the new guys this trick. Put the tire on and torque it. Take the spanner in one hand and use the other as a fist to lightly pound the tire. If you do this while loose you will distinctly notice a rattle sound that goes away when the nut is tight. The idea was to tap on the tire as one overtightens by a quarter turn to seat the bearing. One would then back off half a turn and do the tapping as one found the exact tention that cancels the rattle. Works pretty good. I always error loose, watch how much you are moving the pinch nut. If you can feel play with the tire on then its too loose. Doing this with the tire on improves ones sensitivity to the play whichever way one is observing it.

#6 06-17-2002, 10:07 AM

Thanks for the fyi Steve. I wish I would have asked earlier. I was wondering why Salvo sold them for $6 a piece yet MB wanted $basically $25 a piece. Again, I know the shop needs to make a living to and they do great work...

#7 06-17-2002, 10:21 AM

Thanks for the great info guys!

I think I'll pass on the gauge for now. I won't be buying part for a few weeks, so that might change.

Mike, was that info from the CD or THE manual? Thanks!

MikeTangas · #8 06-17-2002, 11:54 AM

The info is from the CD, but the job number and info are the same whether from CD or paper version of the manual.

You'll find that job on the CD in the 560SEL Chassis section, #33 front axle. Job 300 is the first job listed in section 33.

#9 06-17-2002, 12:08 PM

Thanks Mike!

I'm stuck on campus most of this summer (w/o my laptop) since the buildings I have classes in don't offer wireless connectivity *yet* for my LAN card, so I don't bring software along with me anymore.

I'll check it when I get home tonight. Paper version of the manual would be nice -- Maybe I should check e-Bay more often.

sixto · #10 06-17-2002, 02:54 PM

Should bearings be replaced for the heck of it? I usually clean, grease and go if there's no discoloration or roughness.

Measuring 60 grams of grease is a heck of a lot more difficult than setting wheel bearing preload by feel... if 15K troublefree miles is any indication.

Sixto
91 300SE
87 300SDL

#11 06-17-2002, 03:25 PM

I'll see what they look like. I doubt they've ever been replaced (112k miles)- but you never know until you "get in there".

I have a feeling the rears need it, as the left-rear wheel emanates a high pitched squeak at times, usually around mild turns and coming out of the turns.

haasman · #12 06-28-2002, 09:36 PM

On my "old" 911 the factory manual calls for "being able to move the washer under the axel clamp". The idea being one is to tighten the axel clamp until is just stops, using a screwdriver gently back off the axel clamp until the washer underneath is free to move.

I usually do it the other way: Tighten until the underlying will no longer move. Never had a problem.

How about a quick Nit Wit Story? Years ago in a shop there was a young and very inexperienced tech who had just cleaned wheel bearings and then was blowing them dry with compressed air.

He got the bearings spinning really fast and they made an incredible turbine noise. Also so fast they disintegrated the bearing case and exploded all over the shop. Took out two windows and dented two cars. Remarkably he wasn't touched in his glee of watching and listening to the spinning bearings.

Lesson: Don't spin bearings with compressed air. Use it to clean and dry them only.

OK, the Nit Wit was me ....