Front Wheel Bearings W123 '81 300D---Can Just About Any Mechanic Do This? - PeachParts Mercedes-Benz Forum

iladelf · #1 05-31-2017, 02:13 AM

Reason I ask is, after reading some DIYs posted here, I'd rather not mess with doing so. I have a loud, groaning noise that the place I bought my tires from says was coming from the right front wheel bearing. Spinning the tire in front of me, it seems he is correct in the diagnosis. However, that shop didn't feel comfortable doing the work on my '81 300D (gee, where have I heard THAT before!).

What I'm asking is this; should any reasonable mechanic be able to do this repair, regardless of experience with an older Mercedes like this? Yes, this job looks more difficult than other wheel bearing replacements, but I'd think a wheel bearing replacement is a wheel bearing replacement, regardless of make or model of vehicle.

Further, I assume the original tech was correct in diagnosis? The car makes a whirr-whirr-whirr groaning noise that is especially noticeable between 30-35 mph. He also claimed nothing wrong with the newer front tires.

Kind folks, I await your responses.

NZScott · #2 05-31-2017, 04:35 AM

Anyone who knows what they're doing can do the job. Does that help

1983/300CD · #3 05-31-2017, 06:25 AM

Well, a trained monkey can do it, but not everyone can do it correctly.

There is a pre-load put on the bearings, measured by a gauge when done by the Mercedes people. The average Joe will tighten the clamping nut until the wheel stops spinning, back it off 1/3 turn again, hit it with a mallet, then lock that hub nut down.

How particular are you?

If your mechanic doesn't have the gauge, your "winging it" is as good as his.

jake12tech · #4 05-31-2017, 07:31 AM

Your mechanic seriously won't do the wheel bearing?

Do it yourself. It took me 30 minutes. I had the rotor and caliper off, used a socket, extension and rubber mallet to change the wheel bearings and packed them. I don't have a gauge and I put mine on like the method mentioned above.. Not scary at all. Tell your mechanic to start fixing bicycles instead. You don't really need a gauge unless you're extremely particular.. I put 10K on mine and my S&S is really tight on all my cars.

tyl604 · #5 05-31-2017, 08:56 AM

Interesting how some things do not change. In the early '60's I had a 1957 Chevy. I repacked and replaced the front wheel bearings exactly that way - tightened until the tire stopped turning and then backed off. And I learned it from my dad .

So that technique has been around quite a long time.

moon161 · #6 05-31-2017, 09:11 AM

How did you get the inner race off Jake? Where you able to get under it or did you have to split it?

As for the rest, dead easy, built to be adjusted and maintained. Completely different than the beat the crap out of it for an hour wheel bearing on a suby or honda.

vstech · #7 05-31-2017, 09:28 AM

the inner seal is easy to remove.

My procedure is remove the outer bearing, then put the lock nut back on the spindle.

then pull the rotor until it just touches the nut.

then pop the outer bearing against the nut with your hands pulling on the rotor, and out it pops. easy, and it does not damage the seal.

I have never had any issues popping out the race either. a good drift punch taps it out fairly easy.

vwnate1 · #8 05-31-2017, 10:07 AM

I'd like to add that mooshing grease in the side of the rollers isn't properly packing it ~ you need to put a blob of good quality, short fiber Moly based or synthetic grease on the side of your palm then delicately work the edge of the bearing into it until you see fresh grease oozing out between the opposite side's rollers ~ look on you tube, they show it, it's very easy .

Your FLAPS also sells bearing packers that work very well indeed .

Lastly, the proper wheel bearing adjustment is always done by hand, the torque specification is used first to ensure the bearings are properly set before rotating the hub as you snug up the nut then back it off to allow .002" clearance, most DIY'ers cannot feel this so they back the nut off too far @ 1/3 turn .

When installing seals new or used always use a seal driver, large socket or piece of pipe that touches the seal 360 degrees ~ never tap/strike the seal with your mallet .

In extreme situations you can use a bit of old wood.....

YOU can and prolly will do a better job of this because you care .

Wheel bearing service is actually quite simple so don't be askeert to tackle this, you'll need lots of clean rags and DO NOT spin the bearing with an air hose ! .

moon161 · #9 05-31-2017, 10:15 AM

Quote:

Originally Posted by vwnate1

I'd like to add that mooshing grease in the side of the rollers isn't properly packing it ~ you need to put a blob of good quality, short fiber Moly based or synthetic grease on the side of your palm then delicately work the edge of the bearing into it until you see fresh grease oozing out between the opposite side's rollers ~ look on you tube, they show it, it's very easy .

Your FLAPS also sells bearing packers that work very well indeed .

Lastly, the proper wheel bearing adjustment is always done by hand, the torque specification is used first to ensure the bearings are properly set before rotating the hub as you snug up the nut then back it off to allow .002" clearance, most DIY'ers cannot feel this so they back the nut off too far @ 1/3 turn .

When installing seals new or used always use a seal driver, large socket or piece of pipe that touches the seal 360 degrees ~ never tap/strike the seal with your mallet .

In extreme situations you can use a bit of old wood.....

YOU can and prolly will do a better job of this because you care .

Wheel bearing service is actually quite simple so don't be askeert to tackle this, you'll need lots of clean rags and DO NOT spin the bearing with an air hose ! .

Bearing play has an extra zero in there. .0002"-.0005", I think. The shop manual has the spec in mm, remember to convert. You can get a cheap dial indicator that reads .001" resolution and estimate 1/2 division, or I got one showing tenths at a flea market.

1983/300CD · #10 05-31-2017, 10:28 AM

Quote:

Originally Posted by vwnate1

... most DIY'ers cannot feel this so they back the nut off too far @ 1/3 turn .

Can you feel .0002"? What kind of accuracy do you think you can feel?
How far off from spec is 1/3 turn, usually?

vwnate1 · #11 05-31-2017, 10:35 AM

When you do this for a living for three decades, yes you can feel .002" .

I'd like to see even _one_ mechanic who's ever used a dial indicator to set wheel bearings .

The Factory/Dealer training method was to use a flat bladed screwdriver to push the flat thrust washer back and forth ~ you can feel how much drag there is......

Zulfiqar · #12 05-31-2017, 11:00 AM

The OPs experience is spot on. most shops dont know what a taper bearing is nowadays as they are trained to just swap out entire parts and thats supposed to be a repair. The mechanic will probably be shocked to see a 2 piece dry bearing in the packet.

kuene · #13 05-31-2017, 11:12 AM

I had zero experience as a mechanic. My father-in law showed me how to do it by feel - then when I replaced all my brake components (and didn't have a dial gauge) I did it by feel. It's not rocket science, the tolerances on a 35 year old car are all pretty loose by now anyway.

barry12345 · #14 05-31-2017, 12:29 PM

A few simple rules apply to changing this type of bearings and races out. Do it yourself is not a great issue as the tool requirements are small and common.

Same as changing out most trailer bearings basically. It is somewhat hard to believe any working mechanic would be unfamiliar with doing it.

jake12tech · #15 05-31-2017, 12:33 PM

Quote:

Originally Posted by moon161

How did you get the inner race off Jake? Where you able to get under it or did you have to split it?

As for the rest, dead easy, built to be adjusted and maintained. Completely different than the beat the crap out of it for an hour wheel bearing on a suby or honda.

I remove the locking nut, outer bearing and remove the hub off the spindle (this applies to w210, w124 and w123s I'm sure are similar) and knock out the races and reinstall everything using a 27mm socket and extension and rubber mallet. To have everything centered I think I used a brake rotor. I do things my own way. When it comes to motor work, I follow procedure and specs on important things.