Mechanic's Stethoscope
WARNING: This page is about a different car, the 2013 Ford F-550 Super Duty, 2013 Ford F-450 Super Duty, 2013 Ford F-350 Super Duty, and 2013 Ford F-250 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
A mechanic's stethoscope is an inexpensive tool for locating noises in engines and other moving parts. It can be used to help diagnose piston slap, worn gears, faulty valves, coolant pump failure, damaged gaskets, defective bearings and body squeaks.