Nissan Murano Undercarriage Cover

Let's talk about the Nissan Murano's undercarriage cover, sometimes referred to as a splash shield or an engine splash guard. It’s not the sexiest part of your vehicle, but it plays a vital role in protecting critical components from road debris, moisture, and corrosion. This article will dive deep into its purpose, construction, common issues, and replacement procedures, assuming you’re comfortable with basic automotive tools and techniques.

Purpose and Function

The primary function of the undercarriage cover is to shield the engine bay and other underbody components from the elements. Think of it as a protective barrier against:

Road Debris: Rocks, gravel, salt, and other road debris can be kicked up by the tires and cause significant damage to exposed components like the oil pan, transmission, exhaust system, and even wiring harnesses. The cover acts as a buffer, absorbing the impact and preventing these components from being directly hit.
Moisture: Water, snow, and ice can accelerate corrosion. The cover helps to deflect moisture away from sensitive parts, preventing rust formation and extending the lifespan of your vehicle.
Aerodynamics: While not its primary function on a Murano, the undercarriage cover also contributes to improved aerodynamics. By smoothing the airflow under the vehicle, it can reduce drag and potentially improve fuel efficiency, albeit marginally. The smoother airflow also reduces wind noise inside the cabin at higher speeds.

Beyond these primary functions, the cover also helps to:

Reduce Engine Bay Noise: The cover can absorb some engine noise, contributing to a quieter cabin experience.
Maintain Engine Temperature: By controlling airflow around the engine, the cover can help maintain a more stable engine temperature, especially in extreme weather conditions.

Construction and Materials

Murano undercarriage covers are typically made from one of a few different materials, each with its own pros and cons:

Plastic (Polyethylene or Polypropylene): This is the most common material due to its low cost, lightweight nature, and resistance to corrosion. However, plastic covers are more prone to cracking or breaking upon impact with road debris.
Fiberglass: Fiberglass offers a good balance of strength and weight. It's more durable than plastic but can be more expensive. Cracks are still a possibility, and fiberglass dust can be an irritant if you're working with it.
Metal (Aluminum or Steel): Metal covers are the most durable but also the heaviest and most expensive. They offer the best protection against impacts but are susceptible to rust if not properly coated. You'll typically only find metal covers on vehicles designed for more rigorous off-road use, or as aftermarket upgrades.

The Murano typically uses a plastic undercarriage cover. It's usually secured to the vehicle's frame or subframe using a combination of screws, bolts, and plastic clips (often referred to as push-pin retainers). The design often incorporates ribs or contours to add strength and rigidity.

Common Problems and Issues

Several factors can lead to problems with your Murano's undercarriage cover:

Damage from Road Debris: As mentioned earlier, impacts from rocks, gravel, or even roadkill can crack or break the cover. This is the most common issue.
Loose or Missing Fasteners: Over time, screws and bolts can loosen due to vibration, or the plastic clips can break or become brittle. This can cause the cover to sag or even detach completely. A sagging cover can scrape against the road, causing further damage.
Oil Leaks: Oil leaks from the engine or transmission can saturate the cover, weakening the material and eventually causing it to degrade. Plus, an oil-soaked cover is a fire hazard, albeit a small one.
Corrosion: If you live in an area with heavy road salt usage, corrosion can weaken the mounting points and hardware, leading to premature failure.
Improper Installation: If the cover was removed for maintenance and not reinstalled correctly, it may not be properly secured, leading to damage or detachment.

Diagnosis and Inspection

Identifying a problem with your undercarriage cover is usually pretty straightforward:

Visual Inspection: Look for cracks, breaks, sagging, or missing fasteners. Pay close attention to the areas around the mounting points.
Listen for Unusual Noises: A loose or damaged cover can rattle or scrape against the road, especially at higher speeds.
Check for Oil Leaks: Inspect the cover for signs of oil saturation. If you find oil, trace it back to the source and address the leak.

To get a good look, you'll need to safely lift the vehicle. Use jack stands to support the vehicle; never work under a vehicle supported only by a jack. A creeper can make the inspection more comfortable.

Replacement Procedure

Replacing a Murano undercarriage cover is a relatively simple DIY project, but it’s important to do it correctly. Here’s a step-by-step guide:

Gather Your Tools and Materials: You'll need a new undercarriage cover (ensure it's the correct part for your Murano's year and trim), a socket set, a screwdriver set (both Phillips and flathead), pliers (for removing stubborn clips), safety glasses, gloves, and potentially a creeper. You might also need penetrating oil to loosen stubborn bolts.
Safely Lift the Vehicle: As mentioned before, use a jack and jack stands to lift the vehicle safely. Ensure the vehicle is stable before proceeding.
Remove the Old Cover: Locate all the screws, bolts, and clips securing the old cover. Use the appropriate tools to remove them. Be careful not to strip the screws or break the plastic clips. Sometimes, the clips can be difficult to remove. Use pliers and a gentle twisting motion to coax them out. If a clip is particularly stubborn, you might need to use a clip removal tool. Take pictures of the fastener locations before removing the old cover! This will help you remember where everything goes during reinstallation.
Clean the Mounting Surfaces: Use a wire brush or scraper to clean any dirt, debris, or rust from the mounting points on the vehicle.
Install the New Cover: Align the new cover with the mounting points on the vehicle. Start by loosely installing the fasteners, ensuring that the cover is properly aligned. Once all the fasteners are in place, tighten them securely. Do not overtighten! Overtightening can strip the screws or break the plastic clips.
Lower the Vehicle: Carefully lower the vehicle to the ground.
Test Drive: Take the vehicle for a short test drive to ensure that the new cover is securely installed and doesn't rattle or scrape.

Important Notes:

When replacing plastic clips, consider buying a variety pack of automotive fasteners. These packs contain a wide range of clips and retainers, ensuring that you'll have the right ones on hand.
If any of the mounting points on the vehicle are damaged, you may need to repair them before installing the new cover. This might involve welding, drilling, or using thread repair inserts.
Consider using anti-seize compound on the bolts to prevent them from seizing in the future.

Upgrades and Aftermarket Options

While the factory undercarriage cover is adequate for most driving conditions, you might consider upgrading to an aftermarket option for increased protection, especially if you frequently drive on rough roads or off-road. Aftermarket options often include:

Metal Skid Plates: These are typically made from aluminum or steel and offer superior protection against impacts. They're designed to withstand much more abuse than plastic covers. However, they add weight to the vehicle and can be more expensive.
Reinforced Plastic Covers: Some aftermarket covers are made from thicker or more durable plastic materials, offering improved resistance to cracking and breaking.

When choosing an aftermarket undercarriage cover, make sure it's specifically designed for your Murano's year and trim. Also, consider the weight and ease of installation.

Preventative Maintenance

To prolong the life of your Murano's undercarriage cover, consider these preventative measures:

Regular Inspections: Periodically inspect the cover for damage or loose fasteners.
Tighten Loose Fasteners: Tighten any loose screws or bolts promptly.
Replace Damaged Clips: Replace any broken or missing plastic clips.
Address Oil Leaks: Fix any oil leaks as soon as possible to prevent them from saturating the cover.
Avoid Driving Through Deep Water or Snow: Driving through deep water or snow can put extra stress on the cover and increase the risk of damage.

By understanding the purpose, construction, and maintenance of your Nissan Murano's undercarriage cover, you can ensure that it continues to protect your vehicle for years to come. Remember safety first, and don't hesitate to consult a professional mechanic if you're unsure about any aspect of the repair.