Diagnose chirps and squeals with a stethoscope
Ifyou want to be a real car doctor, you’ve got to use the right tools. An automotive stethoscope (sold at any auto parts store) can be the most effective diagnostic tool in your toolbox. It works just like the ones doctors use, allowing you to “hear inside” a mechanical component. The stethoscope we chose comes with two attachments—a metal probe and a sound amplifier (shown at left).
Connect the amplifier attachment to the hose and move it around the engine compartment. That will narrow your search to a smaller area. Then switch to the metal probe (right photo) to locate the exact source of the problem.
Metal probe Touch the scope’s metal probe to the nonrotating part of the suspect component. If it’s worn, you’ll hear an unmistakable metallic sound.