49 CFR § 215.111 - Defective plain bearing.
A railroad may not place or continue in service a car, if the car has a plain bearing -
(a) That is missing, cracked, or broken;
(b) On which the bearing liner -
(1) Is loose; or
(2) Has a broken out piece; or
(c) That shows signs of having been overheated, as evidenced by -
(1) Melted babbitt;
(2) Smoke from hot oil; or
(3) Journal surface damage.