How to Quiet the Interior of an SUV

Undercoating can be a good way to quiet the interior of an SUV.

New SUVs have fresh seals in the door jambs and firewalls to reduce noise and offer a comfortable ride. As the vehicle ages, some seals and joints can leak and allow excessive road noise to enter the cabin interior. The undercarriage and frame of the vehicle can also be blamed for a noisy ride because dust and gravel can travel up and into the passenger compartment. Applying an undercoating and checking the seals and grommets, using products found at most auto-parts stores, can quiet the interior as you drive your SUV.

Things You'll Need

• Silicone sealant
• Rubber adhesive
• Razor knife
• Undercoat spray, three cans
• Gloves
• Painter's goggles
• Particle mask
• Rags
• Tarp
• Newspaper
• Painter's blue tape
• Scrub broom
• High-pressure water nozzle

Instructions

Undercoating

1. Remove all oil, mud and dirt from the undercarriage of the vehicle with a long scrub broom and a high-pressure hose. Let the SUV air dry.

2. Place the vehicle in "Park" or "Neutral" with the emergency brake set. Use a tire iron to loosen the wheel lug nuts. Lift the SUV up with a floor jack and place two jack stands under the rear part of the frame near each wheel, then place two more jack stands under the front part of the frame near each wheel. Elevate the stands to maximum height and finish removing the wheels.

3. Place a tarp under the front of the vehicle. Use tape and newspaper to mask off all paint surfaces from the inside of the wheel wells, including the outside lip. Wrap newspaper around the struts or shocks, the CV joint assembly, the brake lines, any exposed nuts or bolts and any visible front-end suspension parts.

4. Repeat the prep process for the rear-wheel areas by masking off the wheel wells, any brake lines and emergency brake cables leading to the backing plate, the brake-backing plate, shocks, leaf springs, inlets to the gas tank and the fuel lines. Leave the gas tank bare.

5. Move to the middle underside of the vehicle and wrap newspaper around the total length of the drive shaft, the front and rear U-joints, the exhaust pipes and components, the resonators, muffler and catalytic converter. Cover any cables or fuel lines from the front to the rear. Drape paper over the gearbox or transmission housing and tape it securely. Leave all floorboard metal exposed.

6. Shake the undercoat cans vigorously. Starting at the wheel wells, spray two thin coats on the exposed metal with even strokes, building up enough coat layers to form a thick surface film. Apply undercoat to each wheel well, being careful not to spray through any opening or mud flap in the wheel well, which might hit the exhaust manifold.

7. Spray the entire midsection with undercoat spray. Once finished, let the undercoat dry for 24 hours.

Weatherstripping and Circular Grommets

1. Check all of the vehicle's door jambs and rear cargo door for cracked or peeling weatherstripping. Cut out any damaged sections in a clean, straight line with a razor or sharp knife. Purchase matching weatherstripping in a roll at an auto-parts store.

2. Measure the damaged section of weatherstripping and splice in a new piece by gluing it in place with rubber adhesive. Some weather stripping comes with self-adhesive backs.

3. Open the hood and examine all of the circular rubber grommets on the firewall. Wire looms and small hoses run through these grommets and into the passenger compartment. Snug the grommets back into place if any have popped out of the holes or slipped down the wire looms or hoses, or buy replacement grommets at an auto-parts store.

Tips & Warnings

• If you're not sure if a part should be undercoated, err on the side of caution and cover the part before applying undercoating.

• The engine side of the firewall can also be undercoated. Covering all of the lines, wires and hoses that enter into the passenger compartment through grommets takes time, but spray two to three coats on it. Avoid spraying undercoating on the areas near the exhaust manifold and pipes because they will heat up and smell terrible.

• Wear goggles, mask and gloves for protection when applying undercoat.

• Do not lay directly below area where you are applying undercoat, but extend your arm as far as possible and direct the spray pattern upwards

• If you feel dizzy while spraying undercoating, take a break and breathe some fresh air.

References

• Ranger Forums: How to Undercoat Your Wheel Wells