Loose bearings - PeachParts Mercedes-Benz Forum

Rick Hall · #1 01-23-2006, 10:40 AM

Need some help with wheel bearings on my 91 300E. Seems my front wheel bearings loosen within 1000 miles after adjustment. Someone explain to me what I am doing wrong or how to do right. I have repacked wheel bearings and replaced wheel bearings using the procedure in the manual. No matter if I repack or replace, seems the bearings loosen within 1000 miles or less. When I say loosen, I grab the at the top and push/pull vigorously. I can feel movement and hear 'clunk'. I purchased and used a metric dial indicator the last time and tightened to an indicated .02mm. Everything seemed fine for about 750 miles and when I re-checked, loose again. Talking with the local MB techs, seems i may not be tightening the bearings enough on the initial setting. The manual states to tighten bearings until they turn "with effort", loosen and then tighten to .02mm. The MB techs @ the dealership dont use the dial gauge and they say that they have no problems with come backs. Is this true or does every 124 out there have loose bearings?
Any help or suggestions would be appreciated. I have replaced all tie rods, drag link and rebuilt the idler arm. The front end is tight enough that the loose wheel bearings can be felt.

autozen · #2 01-23-2006, 11:41 AM

I concur with the MB techs. I don't use a dial indicator either, but the again you get the feel after several hundred times. I suggest you use the factory method for safety sake. There are two keys to remember. Don't over pack the hub with grease and tighten and back off the nut several times before you set the final preload. Tighten the nut down with about 45 ft lbs, spin the hub, back off the nut, re-tighten to about 45 again, spin the hub, back off the nut, and do this several times before setting the bearing to specs.

Ron in SC · #3 01-23-2006, 11:49 AM

I've never used a dial gauge to check freeplay and I've changed and adjusted front wheel bearings on my 123, 124, and 126 models for over 20 years and I've never had a problem. It's kind of hard to describe how they should feel, but that said I tighten them real tight initially and try to turn hub to get them to seat. Then I loosen and tighten again. Go thru that process several times, then tighten till they are hard to move and then back off maybe 1/2 turn and then turn to tighten till you feel the adjusting nut starting to seat. Then put wheel on and spin it around a few times and then grab tire at top and bottom and feel for freeplay, to do this I remove brake pads. Keep in mind that I'm not a professional but this seem to have worked for me for a very long time.

autozen · #4 01-23-2006, 11:58 AM

Quote:

Originally Posted by Ron in SC

I've never used a dial gauge to check freeplay and I've changed and adjusted front wheel bearings on my 123, 124, and 126 models for over 20 years and I've never had a problem. It's kind of hard to describe how they should feel, but that said I tighten them real tight initially and try to turn hub to get them to seat. Then I loosen and tighten again. Go thru that process several times, then tighten till they are hard to move and then back off maybe 1/2 turn and then turn to tighten till you feel the adjusting nut starting to seat. Then put wheel on and spin it around a few times and then grab tire at top and bottom and feel for freeplay, to do this I remove brake pads. Keep in mind that I'm not a professional but this seem to have worked for me for a very long time.

Well, you do it just like a professional. As a professional, I can't recommend this method, but is how I do it.The only part I would say is not necessary is removing the brake pads, but if that is your comfort level, keep doing it.

Kestas · #5 01-23-2006, 01:01 PM

I believe the only answer can be that the bearing races weren't seated properly. Ron is correct. When you put the nut back on, you're supposed to wrench it hard while turning the wheel (or rotor), until it is difficult to turn the wheel. This seats the races and squeezes the excess grease from the working contact surfaces so the clearance can't creep any further during use. Only then do you set the clearance.

Don't worry about damaging the races this way, they can take it.

lee polowczuk · #6 01-23-2006, 02:00 PM

I am glad you guys do it this way as well... tightening and backing off is the only way I have ever done wheel bearings.... I don't think I have ever replaced one

Bruno_300TE · #7 01-23-2006, 03:08 PM

Hi
If they keep getting loose they might be too worn?
Regards, Bruno

autozen · #8 01-23-2006, 09:55 PM

Quote:

Originally Posted by Kestas

I believe the only answer can be that the bearing races weren't seated properly. Ron is correct. When you put the nut back on, you're supposed to wrench it hard while turning the wheel (or rotor), until it is difficult to turn the wheel. This seats the races and squeezes the excess grease from the working contact surfaces so the clearance can't creep any further during use. Only then do you set the clearance.

Don't worry about damaging the races this way, they can take it.

You're out of your freakin mind. You don't seat races by tightening the nut. You seat races by pressing or hammering them home with a race installer. Then you install the bearings and set the preload by the means that have been described earlier in this thread.

t walgamuth · #9 01-23-2006, 11:15 PM

autozen

i bet he meant to seat the bearings against the race.

tom w

sbourg · #10 01-23-2006, 11:25 PM

Quote:

Originally Posted by autozen

You're out of your freakin mind. You don't seat races by tightening the nut. You seat races by pressing or hammering them home with a race installer. Then you install the bearings and set the preload by the means that have been described earlier in this thread.

Actually, its unlikely that you can sufficiently accurately seat the races using either a press or a drift. Nothing will apply the pressure as evenly as the actual adjusting nut, when a few thousands of an inch clearance is the spec. It IS the races you are seating properly - the bearings do not need 'seating' between their mating parts, so the 45 ft-lb torque would accomplish nothing if this were the case.

Steve

Kestas · #11 01-24-2006, 10:37 AM

Quote:

Originally Posted by autozen

You're out of your freakin mind. You don't seat races by tightening the nut. You seat races by pressing or hammering them home with a race installer. Then you install the bearings and set the preload by the means that have been described earlier in this thread.

You misunderstood me. You don't use the nut to mount races, only to seat them. I happen to be a bearing engineer and this is the terminology we use. I hope I didn't word it such that it can be misinterpreted. Mounting may not be enough to seat the races. And even if they weren't replaced it's always a good idea to take the extra step and make sure they're seated because of any micromovement that can unseat the races, which can happen for any number of reasons.

anthonyb · #12 03-23-2006, 01:11 PM

Quote:

Originally Posted by Kestas

When you put the nut back on, you're supposed to wrench it hard while turning the wheel (or rotor), until it is difficult to turn the wheel.

Out of curiosity, what type of wrench do you guys use on these? I recently did my bearings, and the adjusting nut doesn't fit a hex socket, so it's hard to find a tool to get leverage to tighten the nut. The ends are rounded, which doesn't help.

The reason I'm asking is I think I didn't get one of my bearings cranked down enough.