Rubber Grommet Installation

Written by cassandra tribe
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Rubber Grommet Installation
Cut the grommet for easier installation, unless it is a weatherproof seal. (Zedcor Wholly Owned/ Images)

Vehicles come with several circular openings pre-drilled in the firewall. There are also pre-drilled openings in the wall between the boot and the interior. Some of these openings are used to allow existing wires and cables to pass through into the interior of the car. Other openings are plugged, allowing the owner to unplug them and use them when connecting an aftermarket accessory. Whenever wire or cable is passed through one of these metal walls, it needs to be protected from rubbing against the edges of the hole or their insulation or protective sheathe will wear down. Rubber grommets are used to line the opening and cover the edges of the metal hole. The instructions for rubber grommet installation are simple; it rarely takes more than five minutes to complete the job.

Skill level:
Moderately Easy

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Things you need

  • Work gloves
  • Flashlight
  • Flathead screwdriver (if needed)
  • Rubber grommet
  • Mineral oil (if needed)
  • Box knife (if needed)

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  1. 1

    Put on a pair of snug work gloves to protect yourself from being cut on any metal edges while working. Use a flashlight to locate the hole that would be the best choice for running the wire or cable through and into the car. If the hole is plugged, pry the plug out with the end of a flathead screwdriver.

  2. 2

    Choose a rubber grommet that will fit the hole. Rubber grommets are sized by matching the diameter of the hole in the wall with the diameter of the inside of the opening in the grommet. Do not measure the diameter of the grommet from outside edge to outside edge; these are the wings of the grommet that split to fall over both faces of the metal wall to form the seal.

  3. 3

    Place one side of the grommet against the hole and pry the wing on that side through the hole in the firewall or body wall with the end of a flathead screwdriver. One wing should go completely through and the other should stay on the other side so that the metal wall is sandwiched between the two. If it proves difficult to pry the rubber wing through the hole in the metal wall, run some mineral oil on the rubber to make it slicker and more supple. Then try it again.

Tips and warnings

  • Cut the grommet completely through on one side with a box knife and roll up the grommet tightly before pushing it through the hole if the grommet is too stiff to do so by prying with the screwdriver. Once the grommet is through, push it back into its original shape to fill the hole.
  • Do not split a grommet that is part of a weatherproof seal (such as grommets placed in a vehicle's firewall). Even a small split can let in cold air and moisture.

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