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Summary
  • Spark plugs create the spark that ignites the air-fuel mixture.
  • Spark plugs are usually pretreated with anti-seize additives before they roll out of the factory. Adding some more can lead to complications in the long run.
  • If one of your spark plugs is seized, then there’s no other option but to replace it.

Your daily driver is made up of thousands of parts, with many of them are so small that you barely notice them at a glance. The thing about these small parts is that they can often cause big problems if left unaddressed, especially if the concerned part is the spark plug.

A Thing or Two About Spark Plugs

Spark plugs are small components that play a big part in the fuel combustion process. They’re generally made from ceramic insulators inside a steel shell with threads creating a gas-tight seal with the cylinder head.

Spark plugs produce the spark that ignites the air-fuel mixture. They create an arc of electricity across two leads without touching but close enough to jump the gap between them.

There are typically three types of spark plugs: resistor, platinum, and iridium.

Resistor Spark Plugs

Resistor spark plugs have a resistor in the center of the electrode, reducing electromagnetic noise and radiation from the ignition system.

These resistors are usually between 2,500 and 7,500 ohms.

Platinum Spark Plugs

Platinum spark plugs have a small amount of platinum on their electrode. Unlike conventional nickel alloy spark plugs, platinum spark plugs don’t react to oxygen, so they won’t erode as fast.

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Iridium Spark Plugs

Iridium spark plugs have a small amount of iridium welded onto the tip of the center electrode. The small amount of iridium helps reduce the amount of voltage required to jump the gap between the center and side electrode.

What Causes a Spark Plug to Seize?

seized spark plugs that have never been removed on high mileage engines
Sometimes spark plugs that have never been removed on high-mileage engines will seize and break and must be dealt with. This 2012 Equinox was sporting the original plugs and one of them broke off as you see. An EZ out worked well for removing the broken part of the plug from the head. | Image Source: Richard McCuistian

Spark plugs get very hot in the normal course of the work they do, and the washer or bevel seat on the spark plug must be in good contact with the head to carry the heat out of the plug.

Aluminum heads are more prone to have seized plugs than cast iron heads because of the different expansion rates of steel and aluminum. Some instructors (for mechanics) teach that engines with aluminum heads should be allowed to cool before removing the plugs, but most mechanics just remove them anyway.

Aluminum heads are more prone to have seized plugs than cast iron heads because of the different expansion rates of steel and aluminum.

– Richard McCuistian, ASE Certified Master Automobile Technician
photo of destroyed cross threaded spark plug
This plug was cross-threaded because it was in a “well” and a student mechanic didn’t have a socket that would hold the plug. So rather than using a piece of fuel line hose to start the plug, he just threw it in the hole, put the socket on it, and hoped for the best. He got the worst. It only took this plug one day and not much driving to be destroyed as you see here. | Image Source: Richard McCuistian

How to Remove Seized Spark Plugs

A steady hand and sufficient knowledge of auto repair are crucial when removing seized spark plugs. If you’re not well-versed in handling this kind of issue, it’s best to leave it in the hands of a trained professional.

Diving into the complexity of this repair without the right tools and information can cause the spark plug to snap, leaving its pieces to drop into the cylinder. Once this happens, you won’t be able to drive your vehicle until all the pieces have been removed.

See also  How to Clean a Spark Plug

But if you’re confident enough to handle the task on your own, here are a few tips that might help.

  • Move the piston to the bottom dead center and let the engine cool down.
  • Use penetrating oil to soak the broken plug shell and wait for a few minutes.
  • Use an easy out to tap into the plug shell head.
  • Use a socket bar to apply counterclockwise pressure to remove the plug.

Anti-Seize for Spark Plugs: Yay or Nay?

Applying anti-seize on spark plugs is usually one thing that drivers consider doing to reduce the risk of having a seized spark plug.

Anti-seize compounds usually come in the form of a paste, grease, or coating with copper or nickel additives. They’re intended to prevent galling, seizing, and corrosion on bolts, flanges, and other metal components that are often exposed to high-temperature environments.

, How to Deal With a Seized Spark Plug: Tips, Causes, and More

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Typically using some light penetrating oil like PB Blaster will do the trick when installing new plugs, but usually this isn’t even necessary. Apply a small amount to the spark plug threads before screwing the plug in. Don’t use motor oil because it will actually cause the spark plug to be very difficult to remove.

Copper-Based Anti-Seize Compounds

Copper-based anti-seize lubricants are made with rust and corrosion inhibitors and antioxidants, making them resistant to saltwater and galvanic corrosion.

This type is mostly used on car parts like brake caliper bleed plugs, conveyor bushings, and gears.

Nickel-Based Anti-Seize Compounds

Nickel-based anti-seize compounds are highly resistant to acidic, caustic, corrosive, and extreme temperature environments.

See also  How to Gap a Spark Plug?

This type of lubricant is generally used on furnaces, high-pressure flange bolts, and crane gears, among others.

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Should You Put Anti-Seize on Spark Plugs?

Anti-seize manufacturers mean well, but using such lubricant can actually damage your spark plugs, according to experts.

Spark plugs are usually pretreated with anti-seize additives before they roll out of the factory. Adding some more can lead to complications in the long run.

Spark Plug Service

If one of your spark plugs is seized, then there’s no other option but to replace it. Here are a few tips on how to successfully replace a bad spark plug.

Tip #1: Always check the service information concerning your spark plugs. Make sure to follow manufacturer-specific instructions and check for technical service bulletins (TSBs) that can affect the new spark plug.

Tip #2: Make sure that the engine has cooled down before removing the spark plugs, especially if your engine has an aluminum cylinder head.

Tip #3: Remove dirt from the spark plug using compressed air or a brush to prevent cylinder contamination.

Tip #4: Check the spark plug gap and correct as needed. Also, make sure not to damage the tip on the center electrode.

Tip #5: Use a thread chaser to clean the threads and install the spark plugs by hand before using a plug socket and torque wrench to tighten them.

About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

NTMS Scientist
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