Ford 2003 Mustang Workshop Manual page 2767

5. Inspect the bearing and raceway for etching.
If etching is present, inspect the seals.
6. Inspect the bearing for heat discoloration (dark blue).
If heat discoloration is evident, check the bearing and race for loss of temper. Draw a file
across the component. If the file cuts the metal, there is a loss of temper.
7. Inspect the bearing for fatigue spalling (metal flaking).