How to Use a Spark Plug Thread Chaser: Engine Ignition Repair Tips

January 27, 2012

An ignition thread chaser or spark plug thread chaser is a handy tool that can serve two purposes for the car enthusiast:

  1. It can help clean the spark plug hole by getting rid of excess grime, dirt and other particles embedded in the thread. This will result in longer thread life and a more efficient operation of the spark plug.
  2. It is used to restore loose threads that may have resulted from cross threading.

Most aluminum heads have the threads carved directly into the metal. Remember that aluminum is softer than other metals and has a tendency to be damaged even with the slightest amount of cross threading. Most mechanics make it a habit to tighten the plugs by hand before using a socket wrench to prevent cross threading, aluminum engine or not. If you wish to clean the spark plug hole using a spark plug thread chaser, you can do so with a few simple steps.

Materials Needed:

  • Spark plug thread chaser (make sure to buy the right size for your engine)
  • Wrench or socket wrench
  • Terry cloth rag
  • Spark plug remover
  • Spray Lubricant

Step 1 - Preparation

Start with a cool engine. Park the car in a well ventilated place with sufficient light. Open the hood and prepare to remove the spark plug wires/hi tension wires according to configuration. Work with one spark plug at a time. Removing all the caps may result in contamination due to the entry of dirt or other particles on the combustion chamber.

Step 2 - Remove the Spark Plug

Use a spark plug remover and/or socket wrench to remove the spark plug. Loosen carefully and with even pressure applied on the socket wrench. This will prevent cross threading and seizing.

Step 3 - Prepare the Thread Chaser

Spray a small amount of lubricant around the grooves of the spark plug thread chaser before use. This will ensure that the metal receives a fair amount of lubrication to help displace moisture and rust that may have accumulated on the threads of the spark plug hole. Wipe off excess lubricant before inserting into the hole.

Tip: Spray the lubricant on a clean towel and wipe on the thread chaser.

Step 4 - Insert the Thread Chaser

Carefully insert the thread chaser into the hole. It is designed to have undersized tap heads that enable it to start in the hole with much accuracy. Initially hand tighten the thread chaser whenever possible.

Step 5 - Wrench the Thread Chaser

Use a wrench to turn the thread chaser through the hole. A spark plug thread chaser will have a driver at the end of the rod. This will enable the larger tap threads to eat onto the grooves of the thread, repairing any minor damage the thread may have accumulated. Do two to four complete revolutions.

Step 6 - Loosen the Thread Chaser

Counter rotate the thread chaser to lift grime and debris off the surface. Pull out and clean with a rag. Repeat steps two through six until all spark plug holes have been cleaned with the thread chaser.

Step 7 - Replace Spark Plug and Ignition Cables

Insert the spark plug and tighten accordingly. Insert the corresponding high tension wires to prevent misfiring and engine damage.

Remember to use the right size of thread chaser for your engine, because the wrong size may damage an otherwise perfect thread.

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