How To Know If My Struts Are Bad

Okay, let's talk struts. You've noticed your ride quality's gone south, or maybe you've spotted some suspicious leaks around your wheels. Time to investigate your struts. Knowing how to diagnose worn-out struts is crucial, not just for comfort, but for safety and handling. This article breaks down the process, giving you the knowledge of a seasoned mechanic.

Purpose: Why You Need to Know This

Understanding how to diagnose bad struts empowers you to:

Save Money: Avoid unnecessary trips to the mechanic and perform the replacement yourself.
Improve Safety: Worn struts compromise braking and handling, putting you and others at risk.
Optimize Performance: Maintain the correct ride height, handling balance, and tire wear.
Enhance Vehicle Longevity: Bad struts can damage other suspension components.

Whether you're tackling a repair, planning an upgrade, or simply want to stay on top of your vehicle's maintenance, grasping strut diagnostics is a valuable skill.

Key Specs and Main Parts

Before we dive into diagnosis, let's identify the key components of a strut assembly. A strut is a crucial part of your car's suspension system, combining the functions of a shock absorber and a suspension support.

Strut Body: The main housing that contains the damper mechanism.
Piston Rod: A metal rod that extends and retracts into the strut body, controlling damping.
Coil Spring: Provides the suspension's primary support, absorbing bumps and maintaining ride height.
Strut Mount (Top Mount): Connects the strut assembly to the vehicle's chassis. Often includes a bearing for smooth steering.
Jounce Bumper (Bump Stop): Prevents the suspension from bottoming out during extreme compression.
Dust Boot: Protects the piston rod and seal from dirt and debris.

Understanding the function of each part will help you pinpoint potential problems.

How It Works

Struts work by converting kinetic energy (motion) into thermal energy (heat). The piston rod moves through hydraulic fluid within the strut body. This movement is resisted by the fluid, creating a damping effect that controls the compression and rebound of the suspension. The viscosity of the fluid, the size of the orifices within the piston, and the overall design of the strut determine the damping characteristics. The coil spring works in conjunction with the strut to provide the desired ride height and spring rate.

When a strut fails, the damping action is compromised. This can lead to excessive bouncing, instability, and reduced control.

Real-World Use: Basic Troubleshooting Tips

Here’s how to assess the health of your struts:

The Bounce Test

This is the classic, but somewhat rudimentary, test. Push down firmly on each corner of your vehicle (over the wheel). Release and observe how the vehicle rebounds.

Good Struts: The vehicle should rebound once and settle quickly.

Bad Struts: The vehicle will bounce multiple times before settling. This indicates a lack of damping.

Important Note: This test isn't always definitive, especially on vehicles with softer suspension setups. A slight oscillation might be normal.

Visual Inspection

Carefully inspect each strut assembly for the following:

Leaks: Oil leaking from the strut body is a clear sign of failure. The seal around the piston rod has likely failed, allowing hydraulic fluid to escape. A small amount of weeping might be acceptable on older struts, but a significant leak is a definite problem.
Damage: Look for dents, bends, or corrosion on the strut body, piston rod, or coil spring.
Worn Bushings: Check the strut mount bushings for cracks, tears, or excessive play. Worn bushings can cause noise and vibration.
Damaged Dust Boot: A torn or missing dust boot exposes the piston rod and seal to contaminants, accelerating wear.
Uneven Tire Wear: Cupping (scalloped wear pattern) on the tires can be a sign of worn struts or shocks. This indicates that the tire is bouncing excessively.

Driving Test

Pay attention to how your vehicle handles under various conditions:

Braking: Does the nose dive excessively when braking? Bad struts can worsen nose dive, increasing stopping distance.
Cornering: Does the vehicle feel unstable or prone to body roll in corners?
Ride Quality: Is the ride harsh, bumpy, or excessively bouncy?
Noise: Do you hear clunking or rattling noises coming from the suspension, especially over bumps?

Advanced Tip: After a drive, carefully feel the strut body. A functional strut will be warm to the touch due to the heat generated by damping. A completely cold strut might indicate that it's not working properly.

Safety Considerations

Working on suspension systems involves several safety hazards:

Coil Spring Compression: Coil springs store a tremendous amount of energy. Improperly compressing or decompressing a coil spring can result in serious injury or death. Always use a properly rated coil spring compressor and follow the manufacturer's instructions carefully. If you are uncomfortable working with coil springs, take your struts to a professional mechanic.
Vehicle Stability: Ensure the vehicle is securely supported on jack stands before working on the suspension. Never rely solely on a jack.
Eye Protection: Wear safety glasses to protect your eyes from debris.
Rust Penetrants: Use penetrating oil to loosen corroded bolts and fasteners.

Always disconnect the negative battery cable before working on any electrical components, especially if the vehicle has electronic suspension components.

Conclusion

Diagnosing bad struts requires a combination of visual inspection, physical tests, and careful observation of your vehicle's handling characteristics. While the bounce test can be a starting point, it's important to thoroughly inspect the struts for leaks, damage, and worn components. If you are unsure about any aspect of the diagnosis or repair, consult a qualified mechanic. Remember that driving with worn struts compromises safety and can damage other suspension components. Prioritize safety, use the right tools, and don't hesitate to seek professional help when needed.

We have a detailed exploded diagram of a typical strut assembly available for download. This diagram provides a visual reference for all the components discussed in this article, aiding in your understanding and troubleshooting. Contact us and we'll happily send it your way.