Brake noise issue resolved (rotor)

 Created by: h_lankford
Orig. Posting Date User Name Edit Date
Oct 9, 2019 06:10PM h_lankford Edited: Oct 10, 2019 09:21AM 
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 Posted: Oct 9, 2019 06:10PM
 Edited:  Oct 10, 2019 09:21AM
Total posts: 1969
Last post: Oct 25, 2019
Member since:Aug 29, 2001
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Last year ( or two ) I posted about an unexplained noise on braking. Both front 8.4 in rotors, flanges, calipers, hoses and pads had been replaced just the year before and all was well, but after only a few hundred miles a strange rotational almost-rubber-like rubbing sound emanated from the left ONLY WHILE BRAKING. Not a metal screeching like a dust shield scraping the rotor. Only on forward, not in reverse. All speeds. Braking seemed reasonably straight.

Pads changed again,, different brands and composition - no help
Caliper replaced (again) - thinking a piston might be sticking - no help
Wheel bearings good, no play, no rumble
Rotor looked fine -at least the outer side . (The inboard side is covered by dust shield that would require too much trouble to take off.)

Finally, I got around to finding the issue:
I removed the caliper, then castle nut, then rotor.
Photo of inboard side of the rotor shows a bluish circular streak suggesting heat damage. Replacing the rotor with a new one (same grade and source) solved the noise problem . There was no scoring of the metal surface, only the discoloration.

I cannot explain this, although admittedly the inboard pad had been tight to fit in, even with the piston pushed all the way in.   Presumably, it may have dragged on the first new rotor enough in those first few hundred miles to overheat the rotor.  Hard to believe, especially since only a part of the rotor was blue and you would think all of its swept area would have been overheated and blue. Whatever the reason, the mystery is resolved.