idiot question regarding wheel bearings
 

I've been thinking about repacking the wheel bearings on my 82 240d. I was thumbing through my hayne's manual to make sure the task wouldn't be too arduous when suddenly I become confused.

The manual specifies that there is a bearing seal on the wheel hub that I must "deform with a screwdriver and then pry off." There is a photo of the step mentioned, showing a man bending the crap out of some kind of ring-shaped object in the hub and then prying it off with a flathead screwdriver.

So I'm curious, is the bearing seal something that I have to purchase and replace, or is it something that can be left off once it's removed, or what?

PS - I'm a moron who knows nothing about cars.

idiot question regarding wheel bearings
 

You are right, the bearing seal will need to be replaced if you butcher it the way the manual states!. Is there a reason you are replacing the bearings in the first place? grinding noises? Here is a suggestion, buy a dolly (no, not one of those inflatable ones!) a 6" X 1/2" diameter brass rod. Must be brass (softer metal than steel, so won't damage bearings!) When you have removed your disk rotor, remove/lift out the ouside bearing. Use the dolly, sliding it in from the ouside of the disk and locate the OUTER lip of the inside bearing, the bearing that lives behind the seal your inquiring about. (not the inside ring of the bearing, or you will trash the bearing). You will feel a lip of about 2mm, use a hammer to strike the dolly and move around the edge of the bearing, striking only the outer edge of the bearing. The seal will pop out eventaully, undamged seal and bearing! Clean all parts in petrol, DO NOT spin the bearingl, you will trash it. When the bearings are clean, check the rollers for scouring marks, collapsed, dull gey wear marks in case hardening etc. If they are still smooth and shiny with all their case hardening intact, repack and replace, you then only need a new seal! (you can reuse the original if it's undamaged at a push) If you intend replacing the bearings anyway, you will need a dolly to drive out the bearing cups if you intend replacing the bearings, so buy a dolly anyway. The waffler- my 2 cents.

Hey thanks.

OH NOES. I found a rust bubble under the black coating behind the front left jack point. I managed to push my thumb through it and (using my index finger) scooped out about two tablespoons of corrosion.

Is my car totalled beyond a doubt, or can this be somehow fixed?

idiot question regarding wheel bearings
 

Does not sound good. The best thing is check the rear jacing point on the same side, if it's sound, jack from that point. You will find a heap of drain holes along the bottom of the sill. Clean them out first with a bit of wire and start hosing out the sill. See what nasties come out. Once it's clean use a thin pointed metal scribe and gently start poking around the front jack point to establish the integrity of the steel and how far the rust has gone. You may have caught it in time. If you start digging madly and it's serious, you could create unnecessary work for yourself trying to hide it before you trade it or off load it. Go slowly, it's probably not too bad, a weak spot for rust in these areas. Check both sills and get an idea of their state first , then make a decision or have a panel beater quote for repairs. Sorry.

There have been some other threads about rusty jack points. You might try searching for them. I used search term "rust jack" and found some.

Seals are considered wear items, and they are hard to remove without damage, hence the procedure for replacing the seals.

If you can remove them wthout damage, as GermanMarque suggested, and they aren't terribly worn, then more power to you and go ahead and reuse the seals.

As for the rest of the procedure, follow the Haynes manual to the letter. Take no shortcuts. Bearings are unforgiving if you do anything less than a perfect job. Post back if you have any more questions or if you don't understand something.

I ordered new bearing seals from Performace Products, along with a few other goodies that I've been meaning to get (cough...my valve cover gasket has been leaking since I bought the car....more than a year ago.)

Completely cleaning the inner bearing parts requires removing the seal, and it will almost certainly be deformed in the process. If deformed only a little, it should be considered junk, so why bother being too careful - you'll only waste time. The seal will come out easily with a little forcing, and the new one needs to be installed by applying very even pressure on the circumference, to avoid damage. A slightly distorted seal will admit water, and the bearings will be destroyed quickly then.

Steve

Wheel bearings
 

Do the same procedures apply for a '93 300E?

The right front wheel was making a loud humming sound when I braked hard.
My mechanic re-packed both front wheel bearings, but the sound was still there. He said I will then need to replace the bearings as the repack did not do the job, although he assured me that the wheels won't fly off!

Now, I want to do it myself, but need to make sure I do it right with this forum's guidance.

Yeah my 240 squeals like a train when braking, I think the bearings are to blame. Am I right?

A squeel or squeak when braking is not a sign of bad wheel bearings. Bad wheel bearings are usually more of a groaning noise which changes in pitch as the vehicle's speed changes, getting higher in frequency the faster you go and usually louder when you turn the wheel in one direction or another. Almost all MBs squeel or squeak when braking if you are using genuine MB parts...it's just their "charm" and is prefectly normal in most cases.

As for the seals, they are widely available for all models, even your '82 240D at chain stores like Pep Boys. They cost about $5 each usually and are well worth replacing if you have to remove the old ones. Chances are they will need replacing anyway and it is cheap insurance.

The real trick in repacking wheel bearings is setting the "preload" correctly after you have packed them and re-installed them. That is, making the set screw just tight enough to take out nearly all of the play without overtightenting them. MB specs call for something on the order of .001" of end play measured by a dial gauge, but I have always done them by feel and never had any trouble.

Just tighten down the screw to seat the bearings, don't over tighten it and spin the rotor as you continue to tighten, when it starts to feel like the hubs are becoming the lightest bit harder to turn then back off on the screw until they turn freely again. Then set the screw with the allen lock. check it again with the wheel on later and make sure there is no excessive "play" in the bearing. Then you will be good to go.

Marty, your writeup is good, but I'd be more aggressive when tightening the hub nut to seat the bearings. The manual instructs the mechanic to tighten the nut until the hub/rotor assembly is difficult to turn. Dont' worry about marring the races - it won't happen. You want to get aggressive with this step, since you definitely want to seat the bearings and not have the clearance grow during use.

I agree with the last two posters, but aggressive preload is needed mostly if the bearings are replaced - to seat the races completely. Also, races often still do not seat completely on the first try, so recheck the clearance after 100 mi or less of driving, and avoid sustained high speed until this is done.

Steve