Backup Copy of Wheel Bearings 1
The following VFAQ was created to help people repack their bearings with fresh grease. As always remember the lovely legal disclaimer that I do not accept any liability for yours or anyone’s actions who may follow any of my guides.
If you are hearing a speed dependant rumbling almost like you have offroad tires you may just as well count on replacing the bearings as well as the races. The bearings shouldn't be replaced without replacing the races as several manufacturers make the parts and they also make them differently, they don't all work together.
This is one of the cleanest messy jobs to do, I plan on going into some pretty good detail such that a person who has never done anything like this before can do it successfully. You absolutely must have everything clean when you make it to the bushings, but you'll have grease all over your hands. My grease, Redline Synthetic CV-2 grease has a little detergent in it so when I get my hand dirty it'll actually clean it off for me. So if your hands get just a little dirty you should be able to take a greasy rag and clean your hands off with it. But if they are pretty dirty then you'll have to go get some dish soap out and clean them off. The Mercedes grease is also supposed to be pretty nice, it comes pre-weighed for a precise amount of grease. If this is your first time or you don't think you'll get the full use out of the Redline grease I'd suggest buying several packets of this stuff. However if the grease in there right now isn't the same as the one you just bought it should be thoroughly cleaned so that the different greases do not mix.
First things first, loosen the lug bolts with a 17mm socket or the 17mm side of a 4way bar. Then lift the car up and support it with a safety jack. I normally stick a little piece of wood in the floor jack's cup and then lift it up on the frame right behind the wheel I'm working on. It is only about a foot or two in, you'll see the big beam, try not to get to close to the end, stay back maybe 4" and center it on the beam. Finish removing the lug bolts, take the wheel off. Next we take off the caliper, there are about 4 bolts back there. Notice the bottom two are for the tie rod arm, don't remove those. The same 19mm socket works on them as well, but we are taking off the caliper here. The caliper should come right off, but if the rotor has a bit of wear on it then you may have to pry the caliper the first little bit to get it off. Now that the caliper is off suspend it with wire from the sway bar. Don't let hang by the hose unless you want to replace that hose very soon.
The hub & rotor assembly have to be taken off the car now so the dust cap has to be taken off. Using a large screwdriver stick it in the lip on the dust cap, tap it away just a little bit and spin it so it is off a little bit everywhere. If you make it come off to quick then it probably won't stay on very well when we are done which will make grease fling all over the rotor and wheel which isn't good for braking or appearance. So just work it off a little at a time until it comes off, normally after it is broken free all the way around it only takes a few more hits all the way around. Under the dust cap you see this weird looking nut with a bolt on it, the bolt is just stopping the nut from spinning. So loosen the bolt just a little bit so the nut can be spun off the spindle. (if you have a little brass radio interference tab take that off and set it in the dust cap just taken off) After this is off carefully pull the hub off, while you won't damage the hub what we are doing carefully here is making sure that front bearing doesn't pop out and land and some dirt. I normally use my thumbs to hold the front bearing into the hub.
Paper towel is excellent for this job as it is messy, needs to be as clean as possible when done, and you get to throw them away when finished. Set the front bearing on a paper towel and place the hub in the vice so the rear seal can be accessed. That seal should be changed, and has to come off to get the inner bearing out to repack it. What I do is take a large flat head screwdriver and pound it into the seal until it dimples, then I pound it in further but mainly push down on it this will pop the seal right out of the hub. If the seal has been in there a long time you may have to do this in two places but generally one works. We aren't mining here we are just skimming the surface such that the screwdriver never hits the bearing.
Now that both the bearings are free of the hub it is a good time to soak them in some stinky gas (funny most people think diesel stinks but after being around it enough you come to the realization that gas is what actually stinks!) to eat all the grease off of the bearing so we can completely refresh it. I normally let it soak like that to weaken the grease up and then finish it off with some carb cleaner which evaporates much faster, plus the pressure blasts any crud through. This is done to both bearings. It is alright if you insist on using an air compressor to accelerate the drying, however hold all of the little pieces so they don't just jet around. Believe it or not but this does run a risk of ruining the bearing.
The bearings are completely cleaned and dry now, pick it up with clean hands. I do the packing itself a little different than most people but it works just the same. I normally use my index finger across a third of the bearing and focus on that area. I push it in on back so it comes out on front, when it is coming through and filling up the front you know it is done. Most people use the palm of their hands or the special grease packing tool which is nothing but a flat surface which creates pressure on one side of the bearing and makes it ooze to the other side. Get the bearings as full as possible with this method, then I also like to spin it a little bit to make sure everything is fine there and that all the rollers are fully lubed up. Again this is done on both bearings. The front generally takes a lot less time than the rear, but really the time involved is very minute.
With the paper towel clean out all the grease you possibly can, this is especially important if you are changing kinds of grease. Please don't use some cheap Valvoline or something like this quality makes worlds of difference here. If the grease has a low drop point it will just flow out of the bearing like a liquid accomplishing very little for the bearing itself. I've been told Mobil1 synthetic has a drop point around 500*F and according to Redline the CV-2 grease has a drop point a little over 900*F and a useful range from -100*F to 500*F which hopefully covers the range it'll be driven in. ;-) Back to the matter at hand, clean everything up until the paper towel comes out clean again. There is to be absolutely no foreign matter in here!! Slop some grease on the races if you are using a cheaper grease the grease almost needs to be built up like a wall such that it can't just flow out when warmed. Again, don't use cheap grease! I'm not sure on the technical data of the Mercedes grease but the packets are measured exactly for what is to be used and is supposed to be a great antifriction grease. Nearly equal amounts on both bearings and then 15g of grease in the dust cap primarily at the bead.
Before we get to far ahead of ourselves here the inner bearing has to be reinstalled with a new seal, I typically put a little bit of grease on this seal then drive it in. I use a fairly large hammer and the largest socket I have, it pushes on the outermost edge of the seal covering as much surface area as possible such that no damage will be done to the seal. The spindle should be wiped off and a thin layer covering the area where the bearings are, then slide the hub on. Again the thumbs holding the outer bearing is a good idea. Just start the nut such that it won't slide off.
The near final and almost most important step (most important is cleanliness) is how tight the hub should be. The rule of thumb for those without the special tools is that you turn the hub until "the hub can be turned with considerable effort only. Then screw clamping nut back approx 1/3 turn and release tension by applying a blow with a plastic hammer against the wheel spindle " Now considerable isn't the best term for the job here, I say when you start to feel it slowing down as you turn it. Then back it up that third. Or the best manner is to feel how free it is when it had no tension on it, it should be that free when you lock the clamping nut. The factory manual suggests checking end play which is if you push then pull on it; it should move less than .02mm. While I haven't scientifically figured out where this point is I figure it is when you push and pull on it and hear nothing. If it is a little loose you hearing the bearings move, if it is tight there is nothing but you feel the resistance turning. I would much rather it be a little bit to loose than to tight, after all when it heats up it expands. Again, no resistance should be felt while spinning, and no clunking noise when pushing and pulling on it. The safest route would be to just spend the $30 on the dial gauge and setup and then you'll know you did it right!
Tighten the bolt in the clamping nut to 14nm, if you'd like you can strike the spindle with a plastic hammer probably not important. Put the 15g of grease on the lip of the dust cap, reinstall the radio interference tab, and then using that same plastic hammer pound on the dust cap. If it went on with one hit you may want a new one, a new dust cap takes a half dozen healthy taps to seat all the way around. Again spin it while you hit the dust cap on. Bolt the caliper back on the spindle (115nm), perhaps use some brake cleaner to clean off the rotor while spinning it. Put wheel back on, torque lug bolts to 110Nm (always across) and lower car, MB recommends rechecking the torque in 75-300miles. I typically do 100ft-lb which is considerably more just to be certain.
Parts: 2 Front Wheel Seals 2 Dust Caps (optional) Bearing grease, don't get cheap here better stuff will last longer and do a better job! Roll of paper towels
Tools: Floor Jack Safety Jack Hammer Plastic hammer Flat heat screwdriver (large) Ratchet, misc. extensions 5.5mm allen socket 17mm, 19mm socket