I may not be an ASE tech, but I've dicked with the front brakes on enough W126s......... backing off a tad just doesn't cut it. The bearings were so loose on my cars they made a Saigon "call girl" appear to be in proper order, using that method. ;)

Spend the extra few dollars for a METRIC readout dial indicator with a magnetic base. You'll be ASTONISHED how far off your bearings are without this device in your tool box.



To the thread maker: do yourself a favor and go back over your work, I had to on my stuff.

Or if a METRIC dial indicator is not readily available, you can use this handy conversion chart.


http://www.yodio.com/yo.aspx?cardid=uvCq9fv1lj55dhUXIEqYX1

Not accurate enough. BTDT.

OK Agreed, after looking at this conversion chart yes it is not accurate enough. However, here is an example of a conversion while replacing rear bearings by dmorrison, seems to work pretty good.

The limits are 0.04-0.06 mm
SAE .0015-.0023Inch
Or 1 mark on my dial gauge is .001 Inch

This shows the dial gauge tolerance I achieved. One is pushing on the hub and other is pulling on it. I have about a .0015 setting.

http://www.peachparts.com/diy/w123rearwheelbearings/27.jpg

Is it your opinion that you should only use a metric dial indicator?

Yes, it's worth the extra dollars up front to save misery down the line. Attempting to convert fractions into Metric is not only a PITA, yet quite inaccurate.

Do a search for my user name and me dicking with my 300SD's front rotors.

May I ask what you may have done differently other then the bearing?

I just took the car on a small 200 mile vaction and everything is still okay.

What are the limits for the front bearing?

Ideally, you want .0005" axial play........basically zero. If you have more than .001, the steering can get a bit sloppy.........if you have less than zero, the bearings are preloaded and their life is shortened rather dramatically.

Driving 200 or 1000 miles after you preloaded the bearings is no assurance that you'll go another 30K miles.

That's right about 0.0125mm. When I tightened mine to that, the wheels got hot after a ~25 mile drive to work. Redid the tolerances when I got home and the feel is back to how it originally felt. Wheels were not hot anymore.

I used a digital gauge instead, was a bit sensitive so it was tricky to get it right. The original bearings were in really good shape, did not smell burnt whatsoever and still had very green grease. Repacked generously and cleaned very thoroughly before installing.

One last question - those 10mm Allen bolts - are they really torqued to only 84lb-ft?

When you say "only 84 lb.-ft."...........how much more do you think you need? It's close to the yield strength of that fastener.

Taking the old ones off took so much more force than 84lb-ft, and we managed to get them all off. Good thing I bought new bolts with blue Loctite.

You're fighting rust and corrosion...........the fastener isn't taking anywhere near the torque you're applying.

With 84 lb.-ft., the fasteners aren't going anywhere............Loctite or not.

This thread was extremely helpful to me and I appreciate all of the passionate input. I am working on my 85 300D. I have my right hub off and need to pick up a 10mm hex nut driver to get the rotor off from the hub. Two remaining questions though:

1) Is there a special grease for the bearings? The stuff in there looks green and I see a reference here to the grease still being green. Is this a special MB product? Can I use another brand or type of grease? Does it need to be hi temp grease?

2) What should I use to clean the bearings? Brake cleaner?

One other comment. There is a reference here to a bearing being too loose and causing steering wheel play. I have steering wheel play so I tightened up the steering box. But when I do that I get a creak. The creak sounds the same as what I heard in my 84 before I had to replace a ball joint. But I can't imagine that I have a ball joint problem because the 85 only has 40K miles on it. It will be interesting to see if after I replace the rotors and set the axle nut correctly, whether this steering wheel play goes away. BTW, the right ball joint looks fine. I have not inspected the left yet.

Also, you may wonder why I am replacing the rotors with only 40K miles. The brake pedal is vibrating a lot when I brake. I assumed that the rotors were warped. Maybe this is from the axle nut being too loose as well. The right rotor did not appear to be warped. I have not seen the left yet. But I don't know if the amount of warpage that would cause the brake pedal to vibrate would be apparent to the eye when looking at it.

Thanks again for all of this great information.

1) I like this grease:

http://www.performanceproducts4benz.com/product.asp?pf_id=P801513&dept_id=5606&cm_mmc=Froogle-_-Car+Care+-+Lubricants-_-P801513-_-X

2) Soak the bearings in a can of paint thinner with some agitation. Follow up with a quick rinse in acetone.

Thanks Brian.

I use a red synthetic grease (forgot the brand) but any decent wheel bearing grease should work.

Coming from the old school, when I cleaned and repacked my bearings the last time, I soaked in gas, shooked it around, dried it and repacked.

As always, when using any flammable liquids, wear proper gloves, keep away from ignition sources and be in well ventilated area.

The problem with backing off the spindle nut by feel or a particular part of a turn is that the starting point or feel is also affected by how tight or loose the 5mm locking bolt is.

How much grease goes in the dust cover?
 

I was refering to a Chiltons manuel as well as the info on this forum to change my front rotors (85 300D). Ciltons says to pack 45-55 grams of grease in the dust cover. I wanted to get an idea of how much a gram is in terms of tablespoons and found that a tablespoon of cooking oil is approx. 14 grams. Does it sound right to put abouit 3 tablespoons of grease in the dust cover. It seem like that would about fill it.

Tightening the clamping nut - how tight?
 

How tight, or how much effort should be used, to tighten the clamping nut to achieve the shop manual described "considerable effort" to rotate the rotor prior to checking end play with the dial gage? (Repair 33.3-300, pg 33.3-300/2)

Specific problem: Right now I'm using "considerable effort" with a 12" crescent wrench to tighten the clamping nut, but my hub/rotor combination still rotates pretty easily. Not "freely" but I can move it using one hand without much effort or clamping force. I have completely removed the small hex bolt, so that's not a factor.

I've reviewed the thread regarding the use of a dial gage and will purchase/borrow one for the final adjustment. My short-term goal is to get my car off the jackstands so I can turn it around in my garage to have access to work on the rear suspension. Since the hub/rotor is currently "snug" on the spindle with a tight clamping nut, I doubt any damage will be done by moving the car the hundred or so feet it'll take to turn it around and get it back in the garage, but I'd like to know if there's something I'm doing wrong so I can fix it during the final adjustment.

Vehicle: '83 300CD
Repair: complete front suspension rebuild - right now front bearing replacement
Current status: good rotors, new bearings and seals, bearing races in the hub were cleaned and inspected prior to re-installing. Spindle was inspected and measured for diameter using a caliper.

New parts are a Hamburg-technic wheel bearing kit, p/n 116 330 0051 OES

I re-packed the inner bearing and installed the grease seal using the O'Reilly Auto parts seal tool (basically a large aluminum disc and a mallet). I was concerned that the new grease seal didn't fit flush or recess into the hub, so I measured both the new grease seal (12.4 mm) and the seat on the rotor (10 mm). Then I measured the old grease seal (13 mm) so I assumed the new seal would be okay. The seal sticking up slightly also matches the cross-sectional drawing on page 33.3-300/3 in my shop manual. It appears to be about 2 mm or so, so I think it's seated but I'm not sure since there's still some room between the inner bearing and the seal.

How tight should the grease seal fit against the inner bearing? Is it likely that I'm trying to fully seat the seal by using the clamping nut so that I'm not really loading the bearings yet? The hub does rotate more freely with the clamping nut loose, so I know I'm doing something by tightening it. The situation is the same on both front wheels.

Any suggestions for what I'm doing wrong, or is this the normal amount of torque required (i.e. a lot)? One pic attached showing wrench position on the clamping nut.

Note: The brake caliper has not been installed yet, so it's not dangling on the hose. Reinstalling the caliper is the next step in the rebuild after the bearings.

Your concerns are valid, but trying to bleed excess fluid while pushing back the pistons is too much of a handful. So when I change my pads, I first bleed out enough fluid to compensate for overfilling the MC by installing new pads (done individually for each wheel). After all new pads are installed, I bleed the entire system and top off at the MC as necessary.

This rear bearing design is nearly identical to the front bearing design on a Porsche 911.

The method I use for tightening that spindle nut, is to use a large flat-head screwdriver. I insert it in the gap (where the 5mm tightening bolt slides through) and crank it down to where it's about as tight as it will go with one-hand-effort. Then I back it off so it's loose, then I turn the screwdriver until the nut just stops on it's own. "zero torque". Just use two fingers. Then tighten the 5mm tightening bolt.

Also, I wouldn't handle the bearings with dirty gloves. I'd put on a fresh pair for handling the bearings and repacking them.

Also for removing the grease cap, I would not use a flat blade screwdriver. That will damage the grease cap and put it out of round. There is a proper bearing cap puller tool out there, but it's pricey. They method I use, is to grab the bearing cap with a channel lock pliers, then whack the channel locks with a mallet.

Nice pictures though!

This hub, rotor, bearing design is nearly identical to the front setup on a Porsche 911. Factory torque spec for those five little rotor bolts on the Porsche is only 18 ft/lbs! Yes really! You should always following the factory recommended torque spec, so if it's 84 ft/lbs on this MB, don't go more or less than that. Do 84 exactly.

Thanks 79Mercy! This is going to come in handy when I do the rotors on my CD. Great writeup and pictures man!

I've learned that no matter what you say on this forum, someone will bite you in the ass about it. I never cleaned, scrubbed, and polished the "brake pad guides" on my car and you know what, it never gave me problems. It's like when you get a car that's been sitting for a while, and just drive off the rust on the rotors.


Thanks for taking the time to make a nice writeup, I appreciate your contribution man.

I know this post is like the oil posts. I would not criticize anyone here. Each person owns there own car and can make decisions about how they want to work on it, and in what manner. I think Brian is very precise in his methods and I appreciate that. I would rather know all the methods used. How successful they were and then I can decide what method I will use. Based on my experience and what tools I own.
With that said, yes a metric dial caliper is preferred. But I don't own one and since I have the Harbor Freight unit, I can easily convert SAE to metric using this program.

http://joshmadison.com/software/convert-for-windows/

It's very accurate and converts down to .000001 inches to whatever you want.



Additionally

I prefer the dial torque method.

I use the Mercedes wheel bearing grease, I know there are other manufacture out there that are just as good.

I always plan on replacing the inner wheel bearing seal, no worries about messing it up and I know its new and won't give me a problem.

I use channel locks to remove the hub cap. Don't distort the cap since that is what holds in the outer wheel bearing grease.

Brake pads and calipers. I always completely clean the caliper and using brake cleaning spray and a brass brush. Clean all of it. I always grease the sides of the pad which allow the pad to move in and out of the rotor as brakes are applied. Just as shown in the manual.

Pressing back the caliper piston. Use the old pad and either channel locks, a pry bar or a screwdriver ( I know, I know!!) to re-seat the piston in the caliper. I do this with the bleed valve open. I want the old stressed fluid out of the caliper. AND I 'll flush the brake fluid anyway to 1. flush it and 2. remove any air that entered the system while pushing back the piston. Using the brake pad to press in the piston, you don't have to worry about going to far or damaging the rubber boot around the piston.

Cleaning the caliper rotor area. It's a little more expensive but I now use P21s to clean the caliper area before starting the job. It removes the dust and buildup very quickly, just as it does on the wheels. So I have started that technique.

Dave

I can't wait to do my own D.I.Y. on this and show how I do it...
getting closer and closer to the point of necessity for me.

I really hate to drag this up again..

But how do you suggest cleaning and packing the inner bearing without replacing the seal?

How bad could it be to mix two greases which are assumed to be in good condition?

1) You can't.

2) Could be quite bad if the grease(s) is not compatible chemically.

I never take the risk.........all the old is removed.........and all the new is installed.

Do it once. Do it right.

The thing about mixing new grease with old is that "High Temp" grease can only be mixed with "High Temp," High friction" with "High friction," etc. The brand is irrelevant.

How bad would it be if you replaced the seal?

devastating.

I just got it out, though I'm quite sure everyone will demand I use a seal press to re-install the new one... that won't be happening.


I also tried the Vstech method of pulling the inner Bearing against the nut.... was not kosher... at least for me.

good info, thanks again.

I had to "perforate" the metal carrier on the seal to get them to release.

I used Valvoline "synthetic" wheel bearing grease, in the grease gun and a Lisle bearing packer. Works like a champ every time.

When I replace the bearings, I replace the race as well.

I tap in the seal using a dead blow hammer or a rubber mallet.

Wheeler Dealer Merc 280SL-Front Brakes
 

http://www.youtube.com/watch?v=dX1P4DwlEiY

Ed China replaces the front brakes and rotors on this 70's 280SL. THe procedure and parts look exactly the same as this DIY, but China does not use a dial indicator, or does he even explain how to reset the locknut on the hub. Nevertheless, its a decent visual of the basic steps required in pulling the used disc off the hub and spindle. Enjoy!

Useful pictures, useful discussion
 

Not being a mechanic, I found the first post's pictures useful in preparing me for what to look for, and the later comments useful for what to do. A few points:

My hardware store didn't have the L-shaped 10mm Allen wrench I wanted, only the little multi-size fold-up type, but they did have a hex driver (its 8" length gave me clearance to work), which turned out to be the best choice, since I needed not only my socket wrench but also a length of pipe to get those Allen nuts loose (while my wife stood on the wheel!)

I cleaned out every bit of old grease (the old gray-black would have clashed with the red jelly look of the new stuff) with rags everywhere I saw it through to the inner bearing, then, since I didn't have any gasoline, I used the brake cleaner spray on everything and I think I got the last bits out with pressure from the spray can.

Don't go with the "back off a third/quarter/etc turn" option: the opinions back and forth prompted me to get a dial indicator and magnetic mount ($25, cheap peace of mind), and I found 1/3 turn was way beyond spec - snugged up by hand then backed off, on my car it took barely an eighth of a turn to stay under 0.12mm end-play.

Keep an old brake shoe to compress the caliper - I had to dig one out of the garbage when nothing else I did made a difference, but with this and a channel lock wrench squeezing it down, it was pretty easy.

I didn't see any evidence of anything like a paste on the backing of the pads, so I didn't use it, but I could go back and add it if there is some technical reason for it. I did use a little bearing grease on the side of the pads, though.

:Moderator EDIT: This is wrong and dangerous, causes excess wear + possible catastrophic bearing failure. :EDIT:...

I just tighten the nut over the bearing as tight as i can possibly get it with a channel lock and then tighten the bolt. It works CRAZY GOOD, for me.

Are you talking about the one held tight by the Allen nut? If you tighten that one all the way as hard as possible, the bearing gets much more wear than if you have the correct endplay. It'll work, but not as long as when correct.

I'm more curious about the reason for the paste some people slather on the back of the discs (and some people don't, like the one's who last changed my car's brakes many thousands of miles ago).

Holy cow
 

I think we should remove each roller from the inner and outer bearings and have them magnafluxed and x-rayed for possible stress cracks or manufactuing voids. Just kidding.

No matter how good or bad the information in this DIY thread is presented it is still likely to beat what really goes in in your typical tire store-slash-brake shop-slash-muffler shop-slash-oil and lube center.

These are the jobs the new guy in the shop gets, and depending on the shop he may have never seen a Mercedes before in his life. I went to Jiffy Lube to get my emmissions test on my 83 240D. The kid performing the test noticed the car was a diesel. He commented that that was cool because "Dang you can tow stuff".

Granted I live in Utah, but still... I think this proceedure as described in this thread will beat what you would get at most shops. Even the guy behind the parts counter at the Mercedes dealer didn't know what a delivery valve oring was and had to call his boss over to help him.

We are all doomed, websites like this and threads like this are the only thing we have left to cling to... snif... snif...

Dial Indicator Help
 

I'm almost ready to perform this job. I have ordered a dial indicator and magnetic base to complete the tolerances on the wheel bearing, hoever I'm confused when reading the tolerances and looking a the dial. I don't know how to read it. I know that my dial is in the form of inches.

So, according to DMorrison the endplay on the rear wheel bearings are as follows:
The limits are 0.04-0.06 mm
SAE .0015-.0023Inch
Or 1 mark on my dial gauge is .001 Inch

the FSM states:
0.01-0.02

Which one do I use? Also, how do I use the numbers on the dial indicator to achieve this?

I understand what the Dial indicator is made to do, I just don't know how to understand the numbers. Thanks

One spec is for the rear; one is for the front.
Which end are you working on?

Guessing that you need the front specs, 0.01-0.02mm = .0004-.0008 in. One half of one increment on you indicator is .0005 in. So be happy with a needle displacement around 2/3 of one increment.

yes its the front end. I found this info helpful on the topic of Dial Indicators, since I never used one before

http://www.mini-lathe.com/measurement/dial_indicators/dial_indicators.htm#Dial%20Indicators

Bearing Grease
 

In my preparation to perform this DIY, I was researching wheel bearing greases. I found this MB site that apparently lists several brands of grease that meet their specifications. MB even included their house brand in the line up. Hopefully others will also find it useful.

http://bevo.mercedes-benz.com/bevolisten/265.1_en.html

How many shop hours?
 

What's the labor time for both front wheels on this procedure?

w123 ...

Pad
Rotor
Bearings
And ... caliper replacement

Would have to include brake bleeding front AND rear, I presume?
Anybody know?

30-45 minutes a side if you've got experience.

actual book hours, no idea.

Hi guys I am halfway through using this diy to replace the (front) calipers, rotors and grease the bearing, but then night fell.
I am replacing the bearing but leaving the old races, next time I'll get them (knocking them out scares me).
My question .. how much grease should be packed in the cavity behind the bearing?
Half full? More? Less?. Apologies if this has been addressed, I'm tired and may have overlooked it.
Much thanks to 79Mercy for posting excellent pictures.

edit: one additional qestion I keep seeing youtube videos of manually working grease into the bearing.. anything wrong with just directing the end of the grease gun into the gap at few places round the rim? Seemed to drive through the grease allright.

The space between the bearings won't provide any lubrication to the bearings if you fill it with grease............you only waste a pile of grease. The bearings themselves need to be "packed" with grease as shown in the video. Directing the grease gun to the area of the bearing does nothing in terms of getting the grease into the rollers. The entire bearing should be packed full of as much grease as you can possible stuff in there. But, anything outside the raceway isn't going to matter whatsoever.

If you put too much grease on the spindle you wont be able to put the hub on.

To pack them by hand wear a pair of medium or heavy duty nitrile gloves and put a nice big dab of grease in your palm and work the grease into the bearing.

In the course of normal driving/braking the hub will get quite warm sometimes. I would think the grease would thin some-what and centrifugal force would bring grease to the hub wall and to the bearings.
On removing a hub I find the grease is nicely distributed on the hub inner wall and the inner sides of the bearings full. Pack the hub with orange wheel bearing grease and the bearings with a compatible black wheel bearing grease then see where the orange stuff ends up.

If the outer bearing is fully packed with grease, where is the orange wheel bearing grease going to go? It cannot go into the bearing if they are fully packed, unless the grease in the bearing moves outward past the outer bearing and into the cap.

The same logic can apply to the inner bearing. The grease seal prevents any migration of grease out of the inner bearing, thereby, effectively, preventing any grease from the space to migrate outward toward the bearing, if it were inclined to do so.

I don't see this happening.

The orange grease will end up against the inside of the bearings and try to fill any voids found. If the bearings are fully packed the orange grease will not enter the bearing.

I'm doing this job now...I'm replacing the left side bearings because, like an idiot, I accidentally pried on one of them while removing the grease seal, deforming the race. Sometimes I'm my own worst enemy. :mad:

FWIW, on the other side I found a good way to remove the seal when it's stuck...stick a small chisel or screwdriver against the edge of the metal part of the seal, where it sticks out of the hub, and tap a couple times to form a divot...then angle the chisel, with the tip in the divot, and tap to force the seal outward. Do this a couple times, 180 degrees apart, and it'll pop out.

Now my question is, does anyone have any slick tricks for getting the old bearing races out? I've been hammering like crazy on those buggers and they won't budge. Maybe I can groove them with a cutting wheel and hit them with a cold chisel, to try to fracture them?

First of all, "hammering like crazy" is the fundamental problem. The races fit with very little interference and do not require much force for removal. They do, however, need to be removed perfectly square with their mounting face.

The act of using a hammer and a drift on one side of the race drives that side forward and jams the race in the hub. If you realize this has occurred, of course you can tap on the opposite side and square the race back up again.

But, most folks do not know whether the race has been knocked out of squareness because it's very difficult to see the size of the gap that develops.

The best procedure is to tap lightly all around the face of the race with a drift and continue this process as it starts to move. Remember, harder hits are not your friend in this situation. Patience is a virtue.