How To Check If Struts Are Bad

So, you think your struts might be on their way out? You're not alone. Struts, along with shocks, are critical components of your vehicle's suspension system, and when they fail, it can impact everything from handling and braking to ride comfort. This guide will walk you through the process of diagnosing strut issues, providing you with the knowledge to determine if replacement is necessary.

Why Bother Checking Your Struts?

Understanding the health of your struts is vital for several reasons. Primarily, it impacts safety. Worn struts can increase braking distances, especially in emergency situations, and negatively affect steering precision. Secondly, it affects ride comfort. Bad struts can lead to a bouncy, unstable ride, making driving unpleasant. Finally, identifying and addressing strut issues early can prevent further damage to other suspension components, like tires and ball joints, saving you money in the long run. Whether you're planning on tackling the replacement yourself or simply want to be informed when you take your vehicle to a mechanic, knowing how to assess your struts is a valuable skill.

Key Specs and Main Parts of a Strut Assembly

Before we dive into the diagnostic process, let's familiarize ourselves with the key components of a strut assembly and some relevant terminology:

Strut Body: The main housing, typically containing the shock absorber, spring, and mounting points.
Shock Absorber (Damper): The hydraulic component that controls spring oscillation and dampens bumps. This uses hydraulic fluid to convert kinetic energy into heat, thus slowing down the movement of the suspension.
Coil Spring: Provides the primary support for the vehicle's weight and absorbs initial impacts. The spring rate is a critical specification, indicating the amount of force required to compress the spring a certain distance.
Strut Mount (Top Mount): Connects the strut assembly to the vehicle's chassis. Often includes a bearing or bushing to allow for steering movement.
Jounce Bumper (Bump Stop): A protective component that prevents the suspension from bottoming out completely, protecting the strut and other parts from damage.
Dust Boot: A protective cover that shields the strut rod from debris and contaminants, extending its lifespan.
Strut Rod: The piston rod of the shock absorber, extending from the strut body.

How Struts Work: A Simplified Explanation

The strut assembly performs two primary functions: it provides structural support for the vehicle's suspension and controls the rate at which the suspension moves. The coil spring supports the vehicle's weight, while the shock absorber dampens the spring's oscillations. When the wheel encounters a bump, the spring compresses. Without a shock absorber, the spring would continue to bounce up and down for an extended period. The shock absorber uses hydraulic fluid to resist this movement, converting the kinetic energy into heat. The fluid passes through small orifices, creating resistance that slows down the spring's motion. This controlled damping is what provides a smooth and stable ride.

Real-World Use: Diagnosing Bad Struts

Here's how to assess your struts for potential issues:

1. The Bounce Test:

This is a simple and often effective preliminary test. Push down firmly on each corner of your vehicle, over the wheel. Release and observe how the vehicle rebounds. A healthy suspension should rebound once and then settle. If the vehicle bounces up and down multiple times, it's a strong indication of worn struts on that corner. This test relies on the shock absorber's ability to dampen oscillations, and excessive bouncing suggests it's lost its damping capability.

2. Visual Inspection:

Carefully inspect each strut assembly for the following:

Leaks: Look for signs of oil leakage around the strut body. A small amount of weeping is normal on older struts, but significant leakage indicates a failing seal and loss of hydraulic fluid, which is critical to its operation. If you see fluid running down the strut, it needs replacing.
Damage to the Strut Rod: Inspect the strut rod for dents, bends, or corrosion. Any damage to the rod can affect its smooth movement and compromise the shock absorber's performance. Make sure the dust boot is in good condition, as a torn boot can allow debris to damage the rod.
Condition of the Mounts: Check the strut mounts for cracks, tears, or excessive wear. Worn mounts can cause clunking noises, vibrations, and poor alignment. Check for rubber deterioration; dry-rotted rubber will appear cracked and brittle.
Condition of the Jounce Bumper: Inspect the jounce bumper (bump stop) for cracks, crumbling, or missing pieces. A damaged bumper can allow the suspension to bottom out harshly, damaging the strut and other components.

3. Road Test:

Pay attention to the following while driving:

Excessive Bouncing: A bouncy ride, particularly over bumps or uneven surfaces, is a classic symptom of worn struts.
Nose Dive During Braking: Excessive forward lean of the vehicle when braking (nose dive) indicates that the front struts are not effectively controlling the weight transfer.
Body Roll During Turns: Increased body roll (leaning) during turns suggests that the struts are not providing adequate support and stability.
Uneven Tire Wear: Cupping or scalloping on the tire tread can be a sign of suspension problems, including worn struts. The strut's inability to maintain consistent contact between the tire and the road surface can lead to localized wear patterns.
Clunking or Rattling Noises: Noises coming from the suspension, especially over bumps, can indicate worn strut mounts or internal strut damage.

4. Professional Inspection:

If you're unsure about your diagnosis, or if you suspect a more complex issue, it's always best to consult a qualified mechanic. They have the tools and expertise to perform a thorough inspection and accurately diagnose any suspension problems.

Safety First: Handling Struts with Care

Caution! Struts contain compressed coil springs, which store a significant amount of energy. Disassembling struts without the proper tools and knowledge can be extremely dangerous and potentially fatal. If you're not experienced with strut disassembly, it's best to leave this task to a professional.

Specifically, the spring compressor tool is designed to safely compress the coil spring, allowing you to remove the strut mount. Attempting to disassemble a strut without this tool can result in the spring suddenly releasing, causing serious injury.

When working on suspension components, always wear safety glasses and gloves. Support the vehicle securely on jack stands before working underneath it. Never rely solely on a jack for support. Consider disconnecting the battery to prevent accidental electrical shorts while working near sensors or wiring harnesses. Also, always follow the manufacturer's torque specifications when reassembling suspension components. Using the correct torque ensures proper clamping force and prevents bolts from loosening over time.

Diagram and Further Learning

We have a detailed diagram available for download that visually illustrates the strut assembly and its components, which can further aid in your understanding. Please contact us to request the file.

By understanding the function and potential problems of your struts, you're better equipped to maintain your vehicle's safety, performance, and ride comfort. Regular inspections and timely repairs will ensure a smoother and safer driving experience.