How to Change the Plugs in a 300C

by Owen Pearson Images

The Chrysler 300C features a 5.7 L HEMI engine that uses 16 spark plugs instead of 4, 6, or 8. There are two spark plugs for each cylinder. If you plan on changing the spark plugs in your 300C yourself, you should set aside an entire afternoon for this task. Although changing the spark plugs in this vehicle is not difficult, it is time consuming.

Step 1

Remove the hex screws securing the plastic engine cover. Lift the cover off and set it aside.

Step 2

Locate the coil plug sets on each side of the engine block. Remove the electrical connector from the plug set closest to you on the passenger's side. To remove the electrical connector, slide the red tab to the left, then depress the center clip and pull up on the connector.

Step 3

Pull up on the secondary boot wire connected to the second plug of the coil assembly. Set the boot aside.

Step 4

Locate the two 10mm bolts holding the coil pack to the engine block. Remove these bolts with a ratchet and a 10mm socket. Gently lift up to release the suction and dislodge the coil pack.

Step 5

Attach a 5/8-inch spark plug socket to an extension bar, and attach the bar to the ratchet. Remove the two spark plugs from the holes in the engine by turning them counter-clockwise.

Step 6

Gap the new spark plugs to 0.045 inches with a gap tool. Spread anti-seize oil on the threads of the new plugs. Insert the new plugs into the holes and tighten by hand. Further tighten the plugs with a ratchet.

Step 7

Replace the coil pack and tighten the bolts. Replace the secondary boot wire and press it into place. Position the electrical connector and press down until the center tab locks. Slide the red tab to the right to secure it in place.

Repeat the process with each of the other seven coil packs.


  • Anti-seize oil is necessary to prevent the fusion on different metals. Without this oil, the spark plugs can permanently fuse to the engine block, making them impossible to remove.


  • Always make sure the spark plug socket is fully seated on the spark plugs when removing or replacing them. The tops of these plugs are ceramic, so they can break easily.

Items you will need

  • Socket set
  • Ratchet
  • Extension bar
  • Spark plug socket
  • 16 replacement spark plugs
  • Gap tool
  • Anti-seize oil

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