How to Use a Bed Liner as Undercoating

Truck bed liners are available in hard plastic, rubber and paint-on versions. Paint-on bed liners use polyurethane and other components to produce a rust-proof and sturdy coating on metal. The benefits of bed liner paint make it ideal for other applications. For example, applying bed liner paint on the undercarriage of your truck can create a layer of sound-proofing, rust-proofing and resistance to extreme temperatures.

Things You'll Need

  • Jack and jack stands, or vehicle ramps
  • Screwdriver, ratchet or pliers
  • Painters' or masking tape
  • Newspaper or tarp
  • String
  • Sandpaper, 150-grit
  • Engine degreaser
  • Stiff brush
  • Water
  • Bed liner paint (Spray-on or brush-on)
  • Paint brush
  • Elevate your vehicle using a jack and jack stands or vehicle ramps to gain full access to the undercarriage. If using a jack and jack stands, elevate one tire at a time, placing the jack stand under the axle of that wheel before elevating the next wheel. If using ramps, make sure to engage the emergency brake before getting under the vehicle.

  • Remove any detachable hardware connected to the frame or undercarriage that may block your ability to paint, such as filters, electric lines, tubes, or spare tires. Use the appropriate screwdriver, ratchet or pliers. If any permanently-attached components cannot be detached from the undercarriage, secure them in a manner that will allow you paint around them. Use string and secure such parts to a jack stand for stability, if desired.

  • Cover any areas you will not paint, such as the engine compartment, wheel wells, and any access holes into the body of the vehicle. Use painters' or masking tape and a tarp or newspaper to tape off areas. Wrap all tubes, electrical lines and components you did not remove with tape and newspaper. If you have a rear drive vehicle, wrap the drive axle and its related parts.

  • Sand the entire area to be painted with 150-grit sandpaper. Sand the frame from front to rear, and then the undercarriage from the firewall to the truck of the vehicle. Clean the area with a degreasing cleanser, a stiff brush and water. Rinse off and allow area to dry fully.

  • Paint the area with the bed liner. If using a spray can, hold the can about 6-inches away from the surface and thoroughly coat the undercarriage. One application is sufficient. If using brush-on bed liner paint, apply one coat with a brush.

  • Follow paint manufacturer instructions for specific drying times. Replace all hardware and remove all tape, paper or tarp from the vehicle once the paint is dry.