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We've all been there. You're driving along and you begin to hear a noise that wasn't there before. You know something might be wrong, but you just can't seem to pinpoint where the sound is coming from. That's why you need a mechanic's stethoscope.
Stethoscopes are normally found in doctor's offices, but they can be useful for diagnosing cars, too. Mechanic's stethoscopes are used for the same purpose as medical versions: to pinpoint sounds and listen in closely on a certain area. In place of a chest piece sits a steel rod, used to place against whatever you think might be the source of the noise or issue.
A mechanic's stethoscope can be used to diagnose all sorts of engine- and drivetrain-related noises, from faulty bearings, to ticking cylinder heads, to knocking crankshafts. Just place the tip of the rod where you think the noise is coming from and listen in, and you'll be a step closer to finding the source of your stress.
I've used mechanic's stethoscopes with success several times with my own projects. It's always a relief to discover that the new, scary noise is nothing more than a belt tensioner bearing or a loose bolt located somewhere in the engine bay. This is one of those tools that you might not think is very useful until you have one at your disposal. You may be reaching for it more often than you think.
Though mechanic's stethoscopes look fancy, they're fairly simple tools, which means they're cheap. You can pick up an example from Pittsburgh at Harbor Freight for just $6.99, complete with an extension piece for those hard-to-reach areas of your engine bay. Gearwrench makes a fancier example you can pick up on Amazon for just under $20.
Road & Track staff writer with a taste for high-mileage, rusted-out projects and amateur endurance racing.
