Cures for a Squeaky Suspensionby Richard Rowe
Ideally, vehicle would only make two kinds of noise: the "vroom" of a revving engine, and maybe a pleasantly deep burble at idle. Beyond that, every single noise a vehicle makes is either an annoyance or a sign that something has gone wrong. Suspension squeaks are tremendously common on older vehicles for the same reason that door and floor squeaks are common on older houses. Most aren't signs of terminal failure, but all make your prize ride sound like an ailing bucket on its last leg.
The Nature of Squeaks
A squeak or chirp is a high frequency sound wave, and requires the same thing that all high frequency waves to: a very rapidly oscillating or vibrating surface that vibrates the air. In an automobile, the inevitable cause of squeaking is a surface moving against another surface, which grabs and releases it thousands of times a second. Anywhere two parts come into contact is suspect, but especially so are places where metal itself vibrates because of contact with other metal, or with rubber. Of course, in application, that means practically every part of your suspension, which can contain dozens or hundreds of moving parts.
Tracking the Squeak
The hardest part about fixing a squeaking suspension may just be figuring out where the sound is coming from. You can stick your head under the vehicle and listen around while someone else bounces the body. But this isn't just dangerous, it's also often ineffective because sound has a way of bouncing around in misleading ways. You may think you're hearing the sound of a spring creaking against the body, when you're really hearing the ball joints 12 inches away. A medical-type stethoscope can be helpful, but it's hard to use, and you run the risk of crushing your fingers. Instead, you can build a simple sound probe using a 12-inch-long, small-diameter metal rod and a small plastic tube. Just slip one end of the tube over the end of the rod, and plug the other into your ear. Touch the other end of the rod to the suspect area while an assistant bounces the vehicle; if you've found the squeak, it will come through probe and into your ear, loud and clear.
Nine times out of 10, suspension squeaks come down to a lack of lubrication between two metal components, or a metal component and a rubber one. If you have a suspension with grease fittings on the ball joints, sway bar end-links and steering links, then start by pumping them all full of grease. There's a good chance that this in itself will solve the problem. The rubber isolators between the tops of coil springs and the spring cubs in the body are also common culprits. Often times, you can stop squeaking here by dropping the springs, and slathering both sides of the isolators with bearing grease; other times, they may be completely worn out and in need of replacement. While you're at it, use a paint brush to grease the coil springs where the coils come close together; worn-out springs will tend to collapse in this area, causing the coils to rub against each other. Really, this means you need new springs -- but some grease will usually quiet the existing springs for a week or two.
Ball joints and suspension bushings will often start to squeak when they're on the verge of failure. These sources are hard to sort out, though, which makes some sort of sound probe critical for finding them. Bad ball joints will generally exhibit more profound symtoms, like thumping over bumps and vibration or vagueness in the steering. Bushings -- the little rubber cylinders between you suspension arms and body or steering knuckle, or sway bar and body -- are often harder to track down. Some have grease fittings, but grease alone won't save a bushing that has been torn to shreds by time and use. These will squeak constantly, because it's effectively rubber rubbing on rubber. For leaf-spring vehicles, check the slide strips between the spring leafs. These can and do wear out over time, causing squeaking. You can tear the spring pack apart and replace them, but replacement spring packs are usually cheap enough that servicing the existing pack generally isn't worth the trouble.
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