Nissan Murano 2009 Bumping Noise In Back When Stopping

The dreaded “bump” from the rear of your 2009 Nissan Murano during braking is a common complaint, and thankfully, often resolvable. This article will delve into the potential causes of this noise, equipping you with the knowledge to diagnose and potentially fix it yourself. We’ll cover the relevant systems, typical failure points, and best practices to keep your Murano stopping smoothly.

Background: 2009 Nissan Murano Braking System

The 2009 Murano utilizes a fairly standard hydraulic braking system. When you press the brake pedal, it activates the master cylinder. The master cylinder pressurizes brake fluid, which then travels through brake lines to each wheel. At each wheel, the fluid pressure forces caliper pistons to clamp the brake pads against the rotor (also called a disc). This friction slows and stops the vehicle.

Key components to understand are:

Master Cylinder: The primary hydraulic pump that generates brake pressure.
Brake Lines: Hydraulic lines transporting brake fluid. These can be steel or rubber.
Brake Calipers: Housing the brake pads and pistons, calipers are responsible for applying pressure to the rotors.
Brake Pads: Friction material that contacts the rotor to slow the vehicle.
Brake Rotors: Metal discs that the brake pads clamp onto.
Parking Brake (Emergency Brake): A separate mechanical system that applies brakes independently of the hydraulic system, typically to the rear wheels.
ABS (Anti-lock Braking System): A sophisticated system that prevents wheel lockup during hard braking, allowing you to maintain steering control. It uses sensors, a control module, and hydraulic actuators.

Technical Breakdown: Potential Causes of the Rear Bumping Noise

The “bump” noise from the rear when stopping can stem from a variety of sources. Here's a breakdown of the most likely culprits, starting with the most common:

1. Worn or Corroded Brake Pads and Rotors

This is the most frequent cause. Over time, brake pads wear down, and rotors can develop rust, corrosion, or uneven wear. This can cause the pads to "grab" or "slip" as they engage the rotor, leading to a noticeable bump. Especially when stopping from low speeds. The bump might be more pronounced after the car has been sitting for a while, allowing surface rust to build up on the rotors.

Diagnosis: Visually inspect the brake pads. If they are worn down to less than 3mm of friction material, they need replacing. Examine the rotors for excessive rust, deep grooves, or an uneven surface. Use a dial indicator to measure rotor runout (warping). Excessive runout can cause vibrations and noise.
Technical Note: Brake pads come in different friction formulations (organic, semi-metallic, ceramic). Each type has its own characteristics regarding noise, stopping power, and rotor wear. Consider the type of driving you do when selecting replacement pads.

2. Loose Brake Caliper Mounting Bolts or Hardware

The brake caliper is bolted to the steering knuckle (also called the spindle or hub carrier). If these bolts are loose, the caliper can shift slightly during braking, producing a bumping or clunking sound. Corrosion or damage to the threads can also prevent proper tightening.

Diagnosis: Visually inspect the caliper mounting bolts. Try to tighten them with a torque wrench to the manufacturer's specifications. If they are loose, be sure to check the threads for damage. If the threads are stripped, you may need to repair them with a thread repair kit (e.g., Heli-Coil).
Technical Note: Always use the correct torque specifications when tightening brake components. Over-tightening can damage the bolts or the caliper housing. Under-tightening can lead to loosening and potential failure.

3. Worn or Damaged Caliper Guide Pins

Caliper guide pins (or slider pins) allow the caliper to move freely as the brake pads wear. They are typically lubricated with a special high-temperature grease. If the grease dries out or the pins become corroded, the caliper can bind, causing uneven pad wear and noise. This binding can manifest as a bump as the caliper finally "breaks free" during braking.

Diagnosis: Remove the caliper and inspect the guide pins. They should slide smoothly in their bores. Clean the pins and bores thoroughly with brake cleaner and apply fresh high-temperature caliper grease. Replace the pins if they are corroded or damaged.
Technical Note: Use only a silicone-based grease specifically designed for brake calipers. Petroleum-based greases can damage the rubber boots that seal the guide pins.

4. Rear Suspension Components: Bushings and Mounts

While less likely to directly cause a "bump" *only* during braking, worn suspension components can contribute to noises in the rear, which can be exacerbated by the change in weight distribution during stopping. Specifically, check the rear shock absorber mounts, trailing arm bushings, and stabilizer bar (sway bar) links.

Diagnosis: Visually inspect the bushings for cracks, tears, or excessive play. Try to move the suspension components by hand. Excessive movement or clunking noises indicate wear. You may need to use a pry bar to assess the bushings more effectively.
Technical Note: Worn suspension components can affect handling and braking performance. Replacing them will improve the ride quality and stability of your Murano.

5. Parking Brake Issues

The parking brake system in the 2009 Murano often uses a drum-in-hat design, where a small drum brake is integrated inside the rear rotor. If the parking brake shoes are worn, damaged, or improperly adjusted, they can cause a bumping or dragging noise, especially when initially applying the brakes. Corrosion can also cause them to bind.

Diagnosis: Test the parking brake's effectiveness. If it doesn't hold the vehicle securely, or if you hear a dragging noise when driving with the parking brake disengaged, inspect the parking brake shoes and hardware. Adjust the parking brake cable tension as needed.
Technical Note: Parking brake cables can stretch over time, requiring adjustment. Follow the manufacturer's instructions for adjusting the cable tension.

6. ABS System Malfunction

Although rare, a malfunctioning ABS (Anti-lock Braking System) can sometimes cause unusual noises or vibrations during braking. If the ABS module is malfunctioning, it might activate inappropriately, causing a brief “thumping” or “bump” sensation. Usually accompanied by an ABS light on the dashboard.

Diagnosis: Check for ABS warning lights on the dashboard. If present, use an OBD-II scanner to retrieve any Diagnostic Trouble Codes (DTCs) related to the ABS system. A faulty wheel speed sensor can also trigger the ABS to activate erroneously.
Technical Note: ABS systems are complex. Diagnosis and repair may require specialized tools and knowledge. Consider consulting a qualified technician if you suspect an ABS problem.

Common Issues and Maintenance Concerns

Rust and Corrosion: Particularly in regions with harsh winters, rust and corrosion can accelerate the wear of brake components. Regular cleaning and lubrication can help prevent this.
Brake Fluid Contamination: Brake fluid absorbs moisture over time, which can lead to corrosion and reduced braking performance. Flush the brake fluid every two years or as recommended by the manufacturer.
Uneven Brake Pad Wear: Uneven pad wear can indicate a problem with the caliper, guide pins, or master cylinder. Address the underlying cause to prevent premature pad wear and ensure consistent braking performance.

Do’s and Don’ts / Best Practices

Do’s:

Use Quality Parts: When replacing brake components, use high-quality parts that meet or exceed OEM specifications.
Lubricate Properly: Use the correct type of grease for brake caliper guide pins and other moving parts.
Torque to Specification: Always use a torque wrench and tighten bolts to the manufacturer's specifications.
Bleed Brakes: After replacing brake components, bleed the brakes to remove air from the system.
Inspect Regularly: Visually inspect your brake system regularly for signs of wear or damage.

Don’ts:

Ignore Noises: Don't ignore unusual noises from your brakes. They could indicate a serious problem.
Over-Tighten Bolts: Over-tightening can damage bolts and brake components.
Use the Wrong Grease: Using the wrong type of grease can damage rubber components and lead to brake failure.
Drive with Worn Brakes: Driving with worn brakes is dangerous and can damage other components.

Conclusion

The "bump" noise from the rear of your 2009 Nissan Murano when stopping is most likely related to worn brake components, specifically the pads or rotors. However, it's crucial to thoroughly inspect all potential causes, including the caliper hardware, suspension components, and parking brake system. A methodical approach to diagnosis, combined with proper repair techniques and the use of quality parts, will help you resolve the issue and ensure the safe and reliable operation of your Murano's braking system. If you are uncomfortable performing these repairs yourself, or if the problem persists after your attempts, consult a qualified mechanic.