49 CFR § 215.107 - Defective plain bearing box: General.
A railroad may not place or continue in service a car, if the car has -
(a) A plain bearing box that does not contain visible free oil;
(b) A plain bearing box lid that is missing, broken, or open except to receive servicing; or
(c) A plain bearing box containing foreign matter, such as dirt, sand, or coal dust, that can reasonably be expected to -
(1) Damage the bearing; or
(2) Have a detrimental effect on the lubrication of the journal and the bearings.