DIY Front and Rear Strut Replacement Guide: 2018 Toyota Mirai

Is your 2018 Toyota Mirai feeling less stable, exhibiting excessive bouncing, or making strange noises over bumps? A DIY front and rear strut replacement guide can help you restore your vehicle's original ride quality and handling performance. Replacing worn struts is a common maintenance item that many DIY owners undertake to save on labor costs, and with the right tools and instructions, it's a manageable project for the mechanically inclined. This guide provides detailed steps specifically for the 2018 Toyota Mirai, ensuring you have the information needed to tackle this important repair.

What drivers notice on this 2018 Toyota Mirai (Symptoms of Worn Struts)

Owners of a 2018 Toyota Mirai often report a noticeable degradation in ride comfort and vehicle stability as the original struts wear out. Given the Mirai's advanced fuel cell electric vehicle (FCEV) platform, maintaining optimal suspension performance is crucial for both comfort and efficiency. Worn struts compromise not only ride quality but also braking effectiveness and tire wear. Here are common symptoms indicating it might be time for a DIY front and rear strut replacement guide project:

• Excessive Bouncing or Swaying: The vehicle continues to bounce several times after hitting a bump or dips excessively when cornering or braking.
• Harsh Ride Quality: Every small bump feels amplified, leading to a jarring and uncomfortable experience.
• Nose Dive or Squat: The front of the car dips significantly during braking (nose dive) or the rear squats during acceleration (squat).
• Uneven Tire Wear: Worn struts can cause tires to wear unevenly, often exhibiting cupping or scalloping patterns.
• Fluid Leaks: Visible oil or hydraulic fluid leaking from the strut body indicates a failed seal.
• Clunking or Knocking Noises: Especially over rough terrain or speed bumps, a clunking sound can signal worn strut mounts or bushings.
• Reduced Steering Control: A general feeling of looseness in the steering or difficulty maintaining a straight line.

At a glance: difficulty, repair cost, and diagnostic workflow

• Difficulty Rating: 6/10 — Moderate
• Common Symptoms: DIY Front and Rear Strut Replacement Guide
• Estimated Repair Cost: $100–$900 (parts + typical shop labor)
• OEM Tooling Required: Standard OBD-II scanner and hand tools

Diagnostic workflow:

1. Confirm the symptom on your vehicle.
2. Scan for stored or pending codes with an OBD-II tool.
3. Inspect the most common causes in this guide (visual checks first).
4. Run verification tests before replacing parts.
5. Repair, clear codes, and verify on a test drive.

Understanding Strut Function and Wear

Struts are a critical component of your Mirai's suspension system, combining the functions of a shock absorber and a structural support for the vehicle. They dampen spring oscillations, control wheel movement, and support the vehicle's weight. Over time, the internal hydraulic fluid can degrade, seals can leak, and internal valves can wear, leading to reduced damping capability. This wear is a natural consequence of mileage, road conditions, and driving style, and it affects both front and rear struts simultaneously.

Verifying Worn Struts on Your Mirai

Before undertaking a DIY front and rear strut replacement guide project, it's essential to confirm that your struts are indeed the source of the problem. This is a purely mechanical issue, so a scan tool is not helpful here.

1. Visual Inspection: Park your Mirai on a level surface and inspect each strut. Look for:
   • Fluid Leaks: Any oily residue or wetness on the strut body.
   • Damaged Boots: Torn or cracked dust boots can allow dirt and moisture to enter, accelerating wear.
   • Rust or Corrosion: Excessive rust on the strut body or spring.
   • Bent Components: Any visible damage to the strut shaft or housing.
2. The Bounce Test: Push down firmly on each corner of your Mirai, then release. A healthy suspension should rebound once or twice and then settle. If it bounces excessively (three or more times), the strut's damping ability is compromised.
3. Road Test: Drive your Mirai on familiar roads, paying attention to how it handles bumps, turns, and braking. Listen for unusual noises and feel for excessive body roll or instability.

While Toyota has issued various Technical Service Bulletins (TSBs) for different models, there are no widespread, specific TSB patterns for premature strut failure on the 2018 Mirai that would indicate a manufacturing defect. Strut wear is generally considered a normal wear-and-tear item.

Essential Tools and Materials

Completing a DIY front and rear strut replacement guide requires a specific set of tools and some replacement parts. Ensure you have everything ready before you start:

• New front and rear strut assemblies (consider quick-struts for easier installation)
• Jack and jack stands (at least 4)
• Wheel chocks
• Torque wrench
• Socket set (metric)
• Wrench set (metric)
• Breaker bar
• Pry bar
• Hammer/Rubber mallet
• Penetrating oil
• Wire brush
• Anti-seize compound
• Spring compressor (if not using quick-struts – exercise extreme caution)
• Gloves and safety glasses
• Brake cleaner

Safety Precautions: Before You Begin

Your safety is paramount. Working under a vehicle can be dangerous if proper precautions are not taken. Always follow these safety guidelines:

• Work on a Level Surface: Never work on an incline.
• Use Jack Stands: Always support the vehicle with sturdy jack stands after lifting it with a jack. Never rely solely on the jack.
• Chock Wheels: Use wheel chocks on the wheels that remain on the ground to prevent the vehicle from rolling.
• Wear Personal Protective Equipment (PPE): Safety glasses and gloves are essential.
• Beware of Springs: If disassembling struts, coil springs are under immense compression and can cause serious injury if not handled with a proper, high-quality spring compressor. Consider using complete quick-strut assemblies to avoid this danger.
• Consult Service Manual: Refer to your Mirai's official service manual for specific torque specifications and additional warnings.

Step-by-Step DIY Front Strut Replacement

This section outlines the general procedure for a DIY front and rear strut replacement guide for your 2018 Toyota Mirai. Always refer to your vehicle's specific service manual for exact procedures and torque specifications.

1. Prepare the Vehicle: Park on a level surface, engage the parking brake, and chock the rear wheels. Loosen the front wheel lug nuts.
2. Lift and Support: Jack up the front of the Mirai and place it securely on jack stands. Remove the front wheels.
3. Disconnect Components:
   • Locate and disconnect any ABS sensor wires and brake line brackets attached to the strut assembly. Use a 10mm wrench or socket for these.
   • Remove the sway bar end link nut from the strut. You may need an Allen key to hold the stud while loosening the nut.
   • Carefully detach the brake caliper and rotor if necessary to gain better access or if specified by your manual. Hang the caliper securely; do not let it dangle by the brake hose.
4. Remove Lower Strut Bolts: Using a breaker bar and appropriate sockets (likely 19mm or 22mm), loosen and remove the two large bolts securing the bottom of the strut to the steering knuckle. You might need to use a pry bar to separate the knuckle from the strut.
5. Access Top Mount Nuts: Open the hood. You'll see three nuts (usually 14mm or 15mm) holding the top of the strut assembly to the strut tower. Do NOT remove them yet.
6. Support and Remove Strut: While supporting the strut assembly from below, remove the three top mount nuts. Carefully lower the entire strut assembly out of the wheel well.
7. Strut Disassembly/Assembly (if not using quick-struts):
   • If using a spring compressor: Securely compress the coil spring until tension is relieved from the top hat. Remove the center nut, then the top hat, spring, and dust boot. Transfer these components to the new strut or install the new quick-strut.
   • If using a quick-strut: Simply install the new complete assembly.
8. Installation: Reverse the removal steps. Guide the new strut assembly into the strut tower, secure the top nuts loosely, then align and secure the lower bolts to the steering knuckle. Reconnect all brake lines, ABS sensors, and sway bar links. Tighten all fasteners to factory torque specifications.

Step-by-Step DIY Rear Strut Replacement

The rear strut replacement process on the 2018 Toyota Mirai is generally similar but often simpler due to fewer attached components.

1. Prepare and Lift: Follow steps 1 and 2 from the front strut guide, chocking the front wheels and lifting the rear of the vehicle onto jack stands. Remove the rear wheels.
2. Access Top Mount: In the trunk or cargo area, you'll need to remove trim panels to access the top strut mount nuts. These are typically under a carpet or plastic cover. Remove the nuts (usually two or three).
3. Disconnect Lower Mount: Locate the single large bolt securing the bottom of the rear strut to the lower control arm or spindle. Use a breaker bar and appropriate socket to remove this bolt.
4. Remove Strut: While supporting the strut, remove the top mount nuts. Carefully compress the strut slightly if needed to clear the mounting points, and remove it from the vehicle.
5. Strut Disassembly/Assembly: Similar to the front, either use a spring compressor to transfer components or install a new quick-strut assembly.
6. Installation: Reverse the removal steps. Install the new strut, loosely secure the top nuts, then align and tighten the lower bolt. Reinstall any trim panels. Tighten all fasteners to factory torque specifications.

Post-Installation: What to Do Next

After completing your DIY front and rear strut replacement guide project:

• Reinstall Wheels: Mount the wheels, hand-tighten lug nuts, lower the vehicle, and then torque lug nuts to specification (typically 76 ft-lbs for the 2018 Mirai).
• Test Drive: Drive slowly at first, listening for any unusual noises and feeling for proper handling. Gradually increase speed.
• Wheel Alignment: This is crucial. Replacing struts significantly alters suspension geometry. A professional wheel alignment is absolutely necessary after strut replacement to prevent premature tire wear and ensure safe handling. Schedule this immediately after the repair.

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Frequently Asked Questions (FAQ)

How long does it take to replace struts on a 2018 Toyota Mirai?

For an experienced DIY mechanic, replacing both front and rear struts can take anywhere from 4 to 8 hours. If you're new to the task, allow a full day, as unexpected challenges can arise. Using quick-struts significantly reduces the time and complexity involved.

Do I need to replace all four struts at once?

While it's often recommended to replace struts in pairs (both front or both rear) to maintain balanced handling, replacing all four at once ensures consistent performance and avoids potential issues where new struts on one axle highlight the wear on the other. Given the Mirai's integrated suspension design, replacing all four is ideal for optimal ride quality and longevity.

What is the difference between a strut and a shock absorber?

While often used interchangeably, a strut is a structural component of the suspension system that combines the functions of a shock absorber and a spring seat, also supporting the vehicle's weight and providing steering pivot points. A shock absorber, on the other hand, is a standalone damping device that only controls spring oscillation and is not a structural part of the suspension.

Disclaimer: This DIY front and rear strut replacement guide is for informational purposes only and is not a substitute for professional advice or hands-on instruction from a qualified technician. Automotive repairs can be dangerous if not performed correctly. Always prioritize safety and consult a professional if you are unsure about any step.

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