How to Remove a Stuck Spark Plug From an Aluminum Head

Changing spark plugs in a car is common during services and tune-ups. If you are doing it yourself, you also don’t want to cause any further damage that will set you back hundreds of dollars. Luckily, mechanics have a few tricks that help them remove stuck spark plugs without much hassle. This article provides a comprehensive guide on removing a stuck plug from an aluminum head.

If your spark plug needs changing, you may find your car misfiring, sluggish, or using up more fuel than usual. This occurs because spark plugs play a significant role in a car’s ignition system. It provides the spark that causes the fuel and air mixture to combust, which powers the engine. Therefore, when you need to change your spark plugs, the last thing you want to deal with is a broken or stuck one. Let’s take a look at how you can deal with this easily.

How to Remove a Stuck Spark Plug?

Whenever working with a stuck spark plug, you have to work carefully. This may take some time and effort. However, it is much better to do it slowly than to be hasty and cause further damage.How to Remove a Stuck Spark Plug From an Aluminum Head

The best method to remove a spark plug is to use rust penetrating oil to loosen the spark plug. You should always begin this process when the engine is cold.

  • The first thing is to clean the spark plug. Remove any dirt stuck to the threads before using rust penetrating oil.
  • Spray the oil on the spark plug base and allow it to penetrate for approximately 30 minutes. If possible, you can also leave it overnight.
  • You can lightly tap the sides of the spark plug to allow the oil to move further into the threads within the aluminum head.
  • As the oil seeps in and the spark plug loosens, tighten it slightly to allow the oil to seep further in. Continue this tightening and loosening method to get the oil as far into the head as it can reach.
  • Then use a wrench to slowly tighten the spark plug to loosen any dirt and rust on the threads before turning it anti-clockwise to remove it. You can continue the back and forth motion of tightening and loosening the spark plug until it easily screws out.
  • If the spark plug is still stuck, you can run the engine for a while until it heats up. The heat should cause the aluminum head to expand slightly, allowing easy separation from the spark plug. However, be sure to remove the spark plug only when it cools down enough to touch it.

Is It Better to Remove Spark Plugs When the Engine Is Cold or Hot?

The engine has to be cold when removing and replacing spark plugs. If you attempt to work with spark plugs while the engine is hot, you will burn your hands and damage the aluminum head. Aluminum expands when heated, and putting in a new spark plug into a hot aluminum head will make them seize together.Is It Better to Remove Spark Plugs When the Engine Is Cold or Hot

This is something to avoid at all costs, making removal extremely difficult. In addition, you risk damaging the aluminum head entirely because it will be malleable in a heated state. Therefore, you should always wait until your engine has cooled down completely before working on the spark plugs.

Can You Use WD-40 to Loosen Spark Plugs?

WD-40 is commonly used to repel water from spark plugs and spark plug wiring. Hence its name – WD stands for water displacement. However, you can use it to prevent corrosion on the spark plug and loosen it during removal. It is worth noting, though, that WD-40 will not remove any corrosion or rust on the spark plug – it will simply help to loosen it.Can You Use WD-40 to Loosen Spark Plugs

Why Would a Spark Plug Be Stuck in an Aluminum Head?

There are a few reasons why this would occur. Fortunately, they are also easily avoidable, and we have listed them below, along with some tips on avoiding them.


Corrosion is a common problem – especially with spark plugs with high mileage on them. The different metal types of the spark plug and the head provide an environment ideal for corrosion as time passes. Therefore, the higher the mileage of your spark plug, the more corrosion will be present and the harder it will be to separate from the aluminum head.

Spark plugs usually have a lifespan of about 100,000 miles. To prevent a build-up of corrosion, you can unscrew your spark plugs at approximately 30,000 miles and spray some anti-seize liquid onto the threads before reinstalling them. This will make removing them more manageable when you are ready to change them at 100,000 miles.

Tightened Too Much During Installation

Another reason for a stuck spark plug is that it was tightened too much when you replaced them. This can cause damage to the threads within the aluminum head. There is no way to know if the spark plug has been tightened too much until it is too late and the damage is done. When installing a new spark plug, you should avoid excessive force to minimize this risk. This is particularly important to remember if you are using the anti-seize spray, as you can easily over-tighten it without noticing.

Cross-Threaded Spark Plug

If the spark plug is cross-threaded, it can set you back quite a bit of money to repair. The risk of damaging the threads of the aluminum head when removing a cross-threaded spark plug is exceptionally high. In addition, you also risk some metal filings from the damaged aluminum head falling into the engine.

To avoid this, you should always thread a spark plug with your hand before using tools. You can ensure that the spark plug is not cross-thread by first turning it in the opposite direction than you would tighten it. This movement allows the spark plug to fall into place on the thread so that you can then tighten them accordingly.

Not Cleaning The Threads

Another step that people often skip is cleaning the threads out before putting in a new spark plug. There could be a build-up of dirt and corrosive materials stuck in the threads on the aluminum head. Therefore, you should always clean out this dirt before putting in a new spark plug.

What Do You Spray on a Stuck Spark Plug?

Good quality rust penetrating oil is best to use on a stuck spark plug, and it will get through any rust build-up and loosen the plug. WD-40 will do this as well but not to the same extent as rust penetrating oil. It takes much longer for WD-40 to work as it will work to loosen rust, and you will have to reapply after you have cleared out the loose dirt constantly.Spray on a Stuck Spark Plug

Some people also use an anti-seize spray when installing new spark plugs. It would be best if you were wary of this practice as it has some consequences. The main issue of concern is that using anti-seize spray makes it easier to over-tighten the spark plug, and it works as a lubricant and can increase torque by up to 20%. That is significant and could cause problems later on when you try removing the plug. Therefore, you should use anti-seize carefully.

When to Seek Professional Help

As much as changing your spark plugs yourself will save you labor costs, you should know when to ask for help. If you cannot remove a stuck spark plug using the straightforward method that this article describes, you should not try to force it. As much as a dealership or mechanic means an extra cost, it will still be less than what you would pay if you damage the spark plug.

Broken spark plugs or damaged heads can cost anywhere between $500 and $1200 to fix, depending on the make and model of your car. Therefore, you should think carefully before using force to remove a spark plug.


Changing the spark plugs in your car is an easy fix. However, having to deal with a stuck spark plug can be frustrating. Luckily, you now know how to remove a stuck spark plug from an aluminum head. Just ensure that you have the right tools and materials. In addition, always remember to work on a cool engine, and be patient when loosening the spark plug.

Using excessive force or working on the spark plug when it is still warm can cause damage to the aluminum head. Ensure that you work cautiously, and if you cannot remove it, maybe it’s time to visit a professional. Remember, though, prevention is always better. Therefore, if you ensure that you install your spark plugs properly, then chances are you won’t have to deal with a stuck spark plug later on.