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Old 03-19-2003, 02:51 PM
Coming back from burnout
Join Date: Jun 1999
Location: in the Pacific Northwest
Posts: 2,274
Brown discoloration on Brake Disk Rotor 83 240D

Now that the days are getting longer and I can do critical service work without a flashlight in 9 degree weather, I can see a brown ring on my brake rotor. The caliper failed on this side.
I dont think my failed brake caliper siezed on the rotor and I dont think my brakes were stuck in a locked braking position and the brakes were not literally smoking.
I think the brake piston got stuck in the retracted postion and ceased to function and provide braking pressure.

Nevertheless my Rotor has a brown ring on it. Should this be indicative of a failed rotor and thermal discoloration? Or is the brown ring a sign of some less severe condition. I always though thermal discoloration of overheated high carbon steel was Blue and not brown...

Brown discoloration on Brake Disk Rotor 83 240D
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Old 03-19-2003, 03:16 PM
Registered User
Join Date: Jul 2001
Location: SoCal
Posts: 1,303
See if it comes off with some steel wool - e.g. organic contaminant or rust.

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Old 03-19-2003, 09:08 PM
I told you so!
Join Date: Jun 2002
Location: Motor City, MI
Posts: 2,817
Discoloration from heat is anywhere from straw to black. The stages are: light straw-straw-purple-blue-black. Brown is hydrated iron oxide. I think you're looking at rust.

Does the car sit idle for long periods? Brakes suffer first on a car that sits unused. If the shiny metal doesn't come back on the rotor surfaces after running it for a couple weeks, then check into the possibility you may have a seized caliper.
95 E320 Cabriolet, 147K
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Old 03-19-2003, 11:02 PM
Registered User
Join Date: Feb 2003
Location: Ontario, Canada
Posts: 3,160
Wash your car & then park it right away.
Look at the rotors the next morning, and you will see the same brown ring ( rust ).
Not much to be concerned about, as you will scrub it off with your first brake application.
2007 C 230 Sport.
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