Abstract: The oil-separating pan of an engine failed during starting testing. In order to find out the failure cause, macro and micro observation on the fracture surface and microstructure examination were carried out. The results show that the fracture surface presented solidification feature after melting, and the fracture mode was overload fracture. The high temperature, which caused serious friction nearby center hole of oil-separating pan, led to grain growing up, grain boundary weakness, melting and cracking in loading direction.