Wheel Bearing Grease Disoloration 96 C280?

[Martineau Gauda]

Hi,

I am preparing to replace the front wheel bearings and races. No noise just over 150,000 miles on orignal bearings.

I removed grease cap from front wheel and looked at the grease. The grease was the original green Mercedes grease but was now very dark, almost black inside the hub. There was no burnt smell. On the front end of the spindle it was the normal bright green color.

Is this discoloration normal with ageing Mercedes grease.

Thanks

[Kestas]

Grease gets black from oxidation at high temperatures. Maybe some contaminants are mixed in. What you saw is normal for a wheel bearing that needs the grease replaced.

Why are you replacing the bearings? Unless there is something wrong with the races and rollers you should just clean, regrease, and replace the seals. Bearing are usually replaced only when they go bad.

[Martineau Gauda]

The new bearings and races are relatively inexpensive and I believe the new ones may be less likely to fail then the ones with 150,000 miles on them. I have the procedure and tools to do the job properly.

I would like to subscribe to the adage “can't hurt, may help” and replace the bearings and races at this time.

Thanks for your help

[Kestas]

I'm glad to hear you're confident of doing a good job. I work in the bearing industry and find that many bearing failures are attributed to improper or abusive installation or improper preload. That's why I caution against replacing a good bearing.

[Martineau Gauda]

Kastas,

Your caveats are well received and appreciated. Apparently, many of the potential problems, especially attention to proper axial play, are shared with the regreasing procedure and the complete replacement procedure, the main difference being proper race removal and installation. I have multiple options to remove the races, 20 ton hydraulic press and special steel alloy and brass punches. I will use a specialized alloy race driver to seat the new races and install the seals.

I have a Snap-On dial indicator and will set the axial play to .0005 inches. (.01-.02 mm) after initial bearing loading. Will recheck after driving.

Thanks for your help