Tool Briefing: Look and Listen

Diagnosing internal engine noise with sound and sight

Another type of device has the microphone mounted in a hollow tube, so it can detect sounds several feet away but remain tightly focused on just one square inch of space. This type often comes with a separate sound emitter that makes a ‘chirping’ noise. When placed inside a closed vehicle, the listening device can be used to find leaks around doors and windows. By fitting a solid wand onto the tube, this device becomes a regular contact stethoscope.

Look inside

A picture may be worth a thousand words, but a picture taken inside an engine could be worth thousands of dollars. On this engine the main timing chain tensioner and water pump sprocket are behind removable covers, perfect for looking inside with a video inspection scope.

Unlike the optical borescope, a video scope uses an electronic camera to create an image on a video screen. Over the past few years the price of the most basic video scope has come down quite a bit. Scopes with more features cost more, but some of those features can be well worth the cost.


Depending on the tool’s features, the video image can be adjusted for lighting conditions, rotated, reversed, zoomed, stored on a memory card as still shots or video, and/or uploaded to a computer with a large viewing screen. This makes it easy to obtain useable color images that eliminate a lot of guessing. You can even email those images to customers when calling for repair authorization.

Among the many different features available, there are a variety of screen sizes and camera head sizes. Those with a larger camera head (typically about 10mm) usually produce a superior image, but those with a smaller head (5.5mm) can reach into tighter spaces. At least one has interchangeable camera heads of different sizes. Some scopes have a removable wireless viewing screen, with a wireless range of up to 30 feet.

The camera wands range in length from 12 to 80 inches or more, and some are watertight. Many have adjustable lighting and/or different colored lights at the camera end, and some have an ultraviolet light to illuminate leak detection dyes. One model has the camera lens on the side of the wand, not the tip.

There are video scopes that connect directly to a computer through a USB port and send their picture directly to the computer screen, but most are stand-alone units with rechargeable battery packs. Battery life has been an issue with some models, but newer models seem to have solved that problem.

When diagnosing engine noises, don’t forget basic techniques like running it with the drive belts removed, dropping the transmission into Drive and checking for broken accessory mounts. Once convinced the noise is internal, electronic instruments that record sounds and sights not only lead to a more accurate diagnosis, the recordings will also document your diagnosis. That fact alone can provide a handsome return on your investment in these state-of-the-art tools.

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