Wheel bearing questions

[amosfella]

On my s320, I was getting my insurance inspection done, and the right front wheel bearings were a little lose. The mechanic gave me 2 weeks to get that fixed. Now, is there a special grease that better to use, or is any lithium based wheel grease good enough??
Also, is a possible to repack the rear bearings which he said were fine, or do they just have to be replaced?? how hard is it to replace those bearings in the rear?? Is that a prevenititive maintenance job if there's no play, or should I wait till there is some play??

[TheDon]

I use a synthetic wheel bearing grease made for disc brakes. As long as it's made for disc brakes you will be good. Rear bearings are generally a pain to deal with.

[Hirnbeiss]

Rears are not repackable, and must be pressed out and in to replace. If they are bad, you usually know due to noise.

[Ferdman]

amosfella, MB dealers sell the proper wheel bearing grease. Proper regreasing calls for the grease to be weighed and split between the inner & outer bearings and inside the cap. The front wheel bearing system is designed so that grease flows through the bearings as the wheel turns. So it's critical that the proper amount of grease be applied to the bearings and inside the cap.

[Can't Know]

This is the first time I've heard of anything to do with grease "flowing" between front wheel bearings -- and I don't recall anything in the WIS about it.

I would use the special "Green" MB wheel bearing grease, it's not that expensive and it does stay where you put it (and it's designed to last a long, long time). Plus it's easy to see when you pop the cover to inspect.

However...if they are loose, there is a chance there is some damage there. You have to disassemble it all anyway to repack them, so you may want to think about just replacing them. Doing the inner races is the worst of that job.

At the very least clean them thoroughly and inspect the rollers and the inner races carefully for any pitting or scarring. Obviously if you note any irregularities, replace them. Either way, a normal (re)packing job, a layer of grease on the face of the race, a bit in the middle if you're so inclined, and that's all you need.

Good luck.

[amosfella]

I already have bearings ordered and races, seal and dust cap as well... Might as well do both sides... I was thinking of getting a set of race drivers off of ebay, but if I get the lathe together, I might just make a driver set as well...

[duxthe1]

I have an opposite opinion on the M/B green synthetic grease. I don't like the stuff. It is a high temp/pressure lube, maybe too much so. I've seen plenty of low mileage wheel bearing failures with it and I attribute it to the green grease not "flowing" as mentioned earlier. It stays sorta waxy and once pushed out of the path of the bearing it doesn't "melt" enough to flow back into the bearings. The result is that the bearings essentially run dry despite grease being in very close proximity. I prefer good non-synthetic grease that will "flow" once the bearings are up to temperature.

[Can't Know]

The green stuff was still in the bearing and in pretty good shape at 112,000 miles on my W210, and cleaning everything showed them to be in fine condition. So I repacked with the green stuff, fit new seals and 17K later it's still fine.

I had some other synthetic wheel bearing grease (mobil1 from a different car), but the real reason I used the green stuff was that if it was good for 112K, I figured I wouldn't have to worry about it for a long time. I also grew up with the old cars and the brown grease that you had to repack every year, but then we were also changing plugs, points and condensers that often, too.

I very rarely hear about the early bearing failures, too, but I have to think that if it were really the fault of the grease, such things would be lots more common.

As I typically say, though, the great thing about owning a car is that you get to decide how best to maintain it, so whatever gives you comfort, go with it.

[amosfella]

I suppose it depends on the climate you live in... If you live in a colder climate, the grease might be too thick, wheras, what might be good for my area of the world, might turn to liquid in texas and run right out the seals...

[amosfella]

I'm planning to take and use a wire brush on a grinder to clean out the kingpins or spindles where the seals seat, in hopes that it will improve the seal life. I plan to scrub it to bare metal....

[Kestas]

I don't think there is anything special about the MB green grease, other than it is likely a high quality grease. Any high quality, heat resistant Grade 2 grease with EP additives should suffice in this application. I doubt there is anything special about the bearing design that would set it apart from other manufacturers and require a special grease.

It's true that bearing designers try to make the grease flow within a bearing.

Your rear bearings are the sealed cartridge type. They are not serviceable. They are replaced when they go bad. If you try to service them, you'll likely destroy the seal and won't find replacements.

Keep in mind that the number one reason for bearing failure is usually faulty installation. If you disturb the front bearings, and they fail shortly afterward, then you probably did something wrong. Rarely is it the fault of the grease. You'd be surprised how little grease is needed to keep a bearing lubed, and how little difference the quality of the grease has on bearing performance.

From my warranty duties, I find the number two reason for autumotive wheel bearing failure is water making its way past the seals. If the seal (or seal wear track) is worn from high mileage, nicked, disturbed, or in any way less than perfect, you can be guaranteed of bearing failure. This is why flood cars often fail all four bearings within a year of being put back in service.

When you say you'll be cleaning the seal seat, I hope you mean the static part (called the "anchor") and not the seal lip contact point. Cleaning the seal lip contact path can put the wrong angle in the grind lines resulting in water being pumped into the bearing. The green or blue paint on the seal body is designed to help seal the anchor surfaces of the bearing.

[amosfella]

by the lip, do you mean the part that contacts the spindle?? And by the anchor, do you mean tthe part that is set into the hub??
Most likely, there is a pile of brake dust caked onto the spindle. That's what I want to clean off...

[Can't Know]

Originally Posted by amosfella

by the lip, do you mean the part that contacts the spindle?? And by the anchor, do you mean the part that is set into the hub??
Most likely, there is a pile of brake dust caked onto the spindle. That's what I want to clean off...

Most of the spindle is inside the hub; that's what the spindle is. There is a machined shoulder at its base; the seal rides up and over that, so once you wipe off the old grease, it should already be pretty clean. If you need to take a wire brush to it, there is something wrong.


Re: Grease "flowing", it absolutely flows within the bearing (it has to), but it's not like it turns to a viscous fluid and flows all around inside the hub and between bearings.

The benefit to any synthetic grease is that it flows better at colder temps, and protects better at higher temps -- without liquefying and running away from the bearing surfaces it is supposed to protect.

[compress ignite]

Ferdman and Kestas for proper technique.(And Elucidation)

BUT,I LOVES this Stuff!

[Will_w202]

My fronts (129 SL) were repacked last week after 19 years and 106k miles on the original green MB grease, which, on the inside of the cap, looked like dried candlewax that had been stuck in the freezer! There was some scoring on the spindle, and some gray ooze of metal shavings deep inside mixed with the remaining "fluid" grease. They were a little loose, and I can tell a difference for sure.

I've found that front shimmy can often be caused by even slightly-loose bearings. On my 124, it was suggested to check pretty much everything plus the kitchen sink (factory part of course ), however the shimmy never went away until the bearings were repacked. It should be a required service after 100k.

What are the symptoms of rear bearing failure? I do have a mystery "hiss" on my car, that is only audible when cruising with the top down at hwy speeds, when I go under a bridge or up beside a wall. As in, the sounds my car is making are then echoed back toward the cockpit. It isn't audible under the hood at idle (pulley, etc) nor during top-up or low-speed driving.