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Why do spark plugs break windows & How to fix them?

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The best way to explain why spark plugs break windows is by understanding how they work: a spark plug creates a high-voltage, low-resistance arc between the center electrode and ground electrode. This arc generates an electric current that heats up the plug.

The heat of this arc can be so intense that it can cause the ceramic insulator on top of the plug to crack or break. Let’s deep dive into it to know more about spark plugs & how they break the car windows!

What is a spark plug?

You may not know it, but spark plugs are responsible for providing the spark that starts your car’s engine. They are also responsible for the pleasant smell of gasoline when you refuel your vehicle. What is a spark plug?

These metal pieces called “spark plugs” are what light up the fuel mixture in gas engines. The process is very simple; when an electrical current is sent through the plug, it emits a high-voltage spark that ignites the fuel in the engine.

Why do spark plugs break windows & How to fix them?

Deep within the recesses of your car engine, a spark plug is doing its job. It has one job – to produce a small electric spark that ignites unburned fuel in the engine’s cylinders. This tiny spark is responsible for starting the engine and powering the vehicle.

So why do spark plugs break windows? Spark plugs are designed to last an average of 8-12 months before needing replacement, but they can still wear down over time even if they are not being used.

In addition, cars are designed to withstand a tremendous amount of stress, and this can cause a spark plug to crack or even break off inside the cylinder head. This can lead to major engine damage, but it can be repaired for a nominal amount of money.

Fixing it might sound easy but it isn’t that simple. You have to use a set of pliers to grab the leads and slowly pull them down away from the plug. You need a screwdriver to get the little clip off. You could get a new cable but that’ll be expensive and you can not guarantee it’ll work.

Can a spark plug break bulletproof glass?

If you’ve ever wondered if a spark plug is powerful enough to break bulletproof glass, it turns out the answer is yes. The reason that spark plugs break windows is that they contain metal particles in the center that can create an electrical discharge when in contact with moisture or water, which in turn causes the window to shatter. This is usually due to condensation forming on the window when it’s cold outside.

What kind of spark plugs break glass?

There are three categories for this:

  • Metal-ceramic
  • Platinum and
  • Platinum alloy engines.

Metal-ceramic engines break glass because of a shortage of oxygen that creates a larger amount of heat that cracks the glass. Platinum plugs work similarly to these sparks but don’t need a lot of heat to break the glass.

Do Ceramic spark plugs break glass?

Many people are unsure if ceramic spark plugs break glass after firing the engine. The truth is that ceramic engine plugs don’t tend to break glass, but they will shatter it. It does not happen often, but it can happen when the plug becomes too hot and causes the glass to expand quickly.

Ceramic plugs are more resistant to breaking than other types of spark plugs, so they are still a better option compared to standard metal coils which have been known to crack windshields upon impact.

What kind of ceramic is used in spark plugs?

It turns out that there are a few different variations, made from different materials. One popular type is made from silicon carbide, which is fired ceramics. This material is very strong but also brittle and breaks easily under tension.

Another type is made from silicon nitride, which is fired ceramics and provides good strength but is quite brittle.

The third type is made from silicon nitride and carbon, which is a high-strength material. This material is fairly brittle and doesn’t break easily under tension, but it has the advantage of being self-lubricating, which means that it will not wear out under normal conditions.

Why does the spark plug work so well at breaking shattered glass?

The spark plug is made of two electrodes of different metals, typically copper and iron. When the metal of the electrodes comes in contact, it creates a spark that generates heat. This heat is enough to break up glass easily.

The best location for a spark plug to break an object is in the center of the object. If you are worried about broken glass on your property, installing a window designed with shatter-proof glass will keep it safe from this type of damage.

If you want to avoid the hassle of removing a damaged window, you can always ask your local window installation company for a service to replace the window.

What if you don’t have a spark plug, and it’s an emergency?

If you find yourself without a spark plug in an emergency situation, don’t worry- it’s a common problem. Most people break their windows while trying to reach for something that is too high to reach. With the exception of some older vehicles, most cars have the spark plug at waist height.

You can reach it by opening your driver or passenger door and leaning inside with either your head or arm. If you lean your head inside and find the plug, it usually can be removed by turning it counter-clockwise.

If the plug is stuck, turn it clockwise until it turns freely. If the plug is stuck in the cylinder when you are outside the car, it is likely that there is a buildup of carbon, either from a previous spark plug replacement or from the combustion of fuel.

If the carbon is loose, it can be pushed out by turning the plug clockwise. If this does not work, gently pull the plug out before it breaks off.

Safety tips when using the spark plug

Before working on the spark plug:

  1. Wear safety glasses and gloves.
  2. Never reach inside the engine while it is still running.

To remove or install the spark plugs:

  1. Use a spark plug socket with a spark plug wrench or a spark plug puller.
  2. Remove any oil filters or oil pump seals.
  3. Place the car on a stand or jack.
  4. Move the car forward a few inches in the direction the engine is turned.


It is clear that spark plugs break windows due to the sheer force and speed of the flame exiting the rear end of the combustion chamber. Due to this fact, it is important to always be mindful of potential locations for a spark plug to land.

-Spark plugs can cause high levels of energy and injury when they break windows; we should be mindful and cautious around these items.

You can also read:

Why Ceramic Is A Material? Why Glass Is a Ceramic?

Rayhan Sarwar

I am a glass and ceramic engineering student at the Rajshahi University of Engineering & Technology (RUET). I enjoy exploring science and technology, which is why I chose to study engineering!

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