Car parts

Carry on baggage
Yes
Checked baggage
Check with carrier

Carry-on baggage: Car parts are permitted if they are empty and cleaned of all fuel. 

Checked baggage: Your air carrier may agree to transport, in checked baggage, either empty equipment that has never contained a flammable liquid or equipment that has previously contained a flammable liquid if specified and adequate measures have been taken to nullify any hazard. Contact your air carrier for specific instructions on the nullification of dangerous goods hazards.