Rick's Free Auto Repair Advice

Diagnose car noises the professional way

Pinpoint the cause of car noises using professional techniques

Guessing is never a good diagnostic strategy. If you’re scouting out the cause of car noises like squeaks, creaks, and squeals, there’s a more professional way to locate the source noise without replacing any parts. I’ll show you how an inexpensive automotive stethoscope is the tool to use to diagnose car noises.

Purchase an automotive stethoscope from any auto parts store or online

They range in price from around $6 to the mid $20. The cheap ones just have a probe, while the better units have an open-air amplifier. Use the amplifier to locate the general area of the car noises. Then switch to the probe to pinpoint the component making the noise. I highly recommend the Lisle 52750 automotive stethoscope kit

automotive stethoscope

On the left is a cheap stethoscope. On the right is the Lisle 52750 professional-grade unit

Start by locating the area of the car noises with a stethoscope amplifier

Attach the amplifier attachment to this Lisle automotive stethoscope (Lisle 52750 Stethoscope Kit). It has a bell-shaped end that picks up and amplifies sound waves. Pop the hood of your car and move it around until the suspect sound gets louder. The amplifier will pinpoint exactly where the car noises are coming from.

Squealing car noise

A squealing sound is usually the sign of a worn belt, a worn idler bearing, a worn pulley, or a misaligned pulley. Use the stethoscope to rule each one of the possibilities in or out. However, DO NOT use belt dressing to solve the problem. Belt dressing is an aerosol spray that coats the belt with a sticky substance. The noise will go away almost instantly. But don’t fool yourself into thinking you’ve solved the problem. That sticky stuff will attract all the road grit, sand, salt, and dust that gets kicked up from under your car. It will stick to the belt and pulley and act like sandpaper, grinding away at all the components.

Before you know it, that “new” belt you just installed will be ready for the garbage can. The idler rollers and pulleys will be so polished from the grit that you’ll be able to see your smiling face in the shine. But when you discover that you’ll have to replace all those components, your smile will quickly disappear.

using auto stethoscope amplifier to listen for car noises

touching stethoscope probe to diagnose car noises

Using an automotive stethoscope probe on an engine valve cover to detect engine noiseIf you have a metallic screeching car noise, switch to the metal probe attachment.

Touch it to the NON-ROTATING part of idler rollers, power steering pump, alternator, A/C compressor, etc.

You’ll definitely be able to detect which bearing is going bad by comparing the bearing noises from one component to another.

Got an engine noise that’s driving you crazy? Use the probe for that too. The probe can pinpoint a bad rocker arm simply by moving it along the valve cover.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat



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