Engines make many noises, and finding a bad pulley or internal knock by ear is difficult. A mechanic stethoscope helps you pinpoint the sound. You place the earpieces in your ears and touch the metal probe to different parts of the engine. The probe transmits the vibration directly to the earpieces, amplifying the sound. You can easily hear a dry alternator bearing or a ticking valve lifter. Keep the probe clear of moving belts and cooling fans.
Mechanic Glossary
Mechanic Stethoscope
A diagnostic acoustic tool with a metal probe and earpieces used to locate internal engine, bearing, and accessory noises.
Frequently Asked Questions
A bad bearing makes a low, continuous growling or whining sound that changes with speed. A valve tick makes a sharp, rhythmic clicking sound.
The metal probe can conduct electricity. Avoid touching alternator terminals, spark plug wires, or battery posts to prevent a shock or short circuit.
While a screwdriver can transmit sound, the stethoscope's earpieces block out background engine noise, making it much easier to hear quiet, internal sounds.