Diagnosing many car problems is easier with an automotive stethoscope, a tool that lets you hear inside the engine. Here's an introduction to using one to track down trouble.
Start with the sound amplifier attachment to locate the general area where the problem is.
Touch the scope's metal probe to the non-rotating part of the suspect component. If it's worn, you'll hear an unmistakable metallic sound.
If you want to be a real car doctor, you've got to use the right tools. An automotive stethoscope 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 (first photo). Use the amplifier to narrow down the source of the noise. Then switch to the metal probe (second photo) to locate the exact source of the problem.
Connect the amplifier attachment to the hose and move it around the engine compartment. That will narrow your search to a smaller area.