GearWrench Mechanic’s Stethoscope GearWrench Mechanic’s Stethoscope locates the source of engine noise quickly, listens for trouble by tracing the sound of flowing water, oil, gas or steam, can identify piston slap, worn gears, faulty valves, water pump failure, damaged gaskets, and defective bearings, and the stethoscope has a shock-resistant handle and disassembles for storage.