| Brown stain on inside of outer rear bearing [message #362255] |
Sun, 07 February 2021 07:39  |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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I pulled the passenger side mid rear hub yesterday to install my Lenzi mid-rear disk brake system. Upon examining the bearings I noted a brown stain on the inside of the outer bearing where it rests on the spindle. Its on about 1/4 of the inside circumference.
See photo here:
http://www.gmcmhphotos.com/photos/lenzi-mid-axle-disk-brake-upgrade/p67915-installing-dave-lenzi-mid-axle-disk-brake-upgrade.html
I don't see any scoring or evidence of heat. The rear bearings where replaced about 2 years ago with new Timken bearings, but with cancer and Covid they have less than 3,000 miles on them.
The grease I used was a Valvoline product for wheel bearings with descriptions "Extreme pressure and temperature with moly and lithium for vehicles with disk brakes" so I'm thinking it should be up for the job. The grease has not separated.
I have not yet cleaned out the entire bearing, but I cannot see any pitting etc.
Any opinions on this brown stain.
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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| Re: Brown stain on inside of outer rear bearing [message #362257 is a reply to message #362255] |
Sun, 07 February 2021 08:47  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Bruce,
Some years back, I lost a wheel (wheel, tire, brake drum and hub) in Arkansas. We searched, but never found the errant piece. There was evidence of moisture - not much - on the spindle. Ever since, I have been very aware of moisture in the rear bearings and have often seen evidence but never seen actual corrosion damage. What that stain may be is the result of a very small amount of moisture that either was left in during the prior assembly or made its way in later. The amount of water that stain represents would have been less than a mm3 (cc/1000).
That brown is the color that is from Fe2O3, I am also seeing the black color of FeO2. FeO2 is the precursor of the brown rust color. The reason that there is some black and some brown is that was all the water that was available. I will end my discussion of the corrosion of iron here because it starts to get complex past here.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Brown stain on inside of outer rear bearing [message #362258 is a reply to message #362255] |
Sun, 07 February 2021 10:07 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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I read that moly when exposed to high temps oxidizes and the oxidized byproducts do not have lubricating properties and in presence of moisture in air promote corrosion of the rubbing surfaces. If you did not set up wheel bearing lash correctly (loosen to pin if needed after finger tightening, never tighten) or overtemped the brakes this could happen.
John Lebetski
Woodstock, IL
77 Eleganza II
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