Spark Plug Blew Out of Cylinder Head: Why and What to Do?

If your spark plug blew out of the cylinder head, it could seem quite annoying and problematic. But, unfortunately, such an issue usually happens with owners of engines with allow cylinder heads. Thus, if it happens to you, you may want to know why it happens and how you can deal with it. So, you may ask:

If the spark plug blew out of the cylinder head, why does it happen, and what should you do about it? In this case, the threads got worn out, or they got cross-threaded or galled. As a result, it caused damaged to your spark plug threads. Another reason is the heat and compression pressure coming from the cylinder. If it happens, you need to ask a mechanic or replace the spark plug yourself.

A blown-out spark plug poses a lot of potential risks and issues to your vehicle. Thus, if it ever happens to you, you need to solve it as soon as possible. If left unchecked, it can lead to a more complex issue, and it can also get quite expensive.

In this article, you’ll see our in-depth take on this issue and also some answers to questions related to this matter. This way, you can understand a bit more about your spark plug and how you should deal with it if it ever blows out.

Without further ado, let’s get into it!

Spark Plug Blew Out of Cylinder Head

What Causes a Blew Out Spark Plug?

There are many possible causes for a spark plug to blow out. However, the main reason why it happens is the improper tightening of the plug.

For instance, a spark plug can blow out when you fasten it too tight to the engine plug. Or, it can also blow out if you don’t tighten it enough that it loosens out.

In general, improper tightening and connection between the spark plug and the engine plug can cause an effect on both parts. If it happens, the spark plug can’t transfer electric charge to the engine. 

In worse scenarios, the failed transfer can cause the spark plug to blow out. Other causes of this issue are overuse and constant dirt getting into the engine.

Can You Drive With a Blown Out Spark Plug?

The short answer is you may, but you shouldn’t drive with a blown-out spark plug. While an engine may run even after the spark plug blowing, it’s not a good thing since the continuous running of the engine can cause extreme damage when the spark plug is down.

In general, take it as a rule of thumb to stop the car if you think that your spark plug blew. If you continue driving, you can’t pull out that plug since it can be scorching.

Moreover, it would be best to let the engine cool to remove the inductor wires and coil from the blown spark plug. If you do otherwise and let the engine run, it can lead to harming your engine.

How Do You Fix a Blown Out Spark Plug?

If you have a blown-out spark plug, you may have thought about fixing it yourself so you can save money from getting a professional to do it.

If you’re familiar with how your spark plug works, you can follow these steps to make sure you’re guided all the time. However, if you’re unfamiliar with this line of work, it would be best to take a step back and have someone do it for you.

Now, if you’re ready to do this, let’s get started.

Clear the entire area. 

The first thing a mechanic would likely do is to start replacing the spark plugs. He will do so by thoroughly clearing the area where it blew. 

Most spark plug issues occur due to a failed reaction to connectors. The primary cause of such a problem is dirtiness.

For this reason, your first step would be to clear everything out and make sure they are clean all around. It will also help you improve your engine’s performance, even by just a bit if it’s all dirty.

Check the spark plug.

After cleaning the area, you need to look for signs of a worn-out or blown-out spark plug. In general, an old plug that needs replacement will appear quite dark. If you see such an appearance, you can say it needs replacement.

As soon as you think so, you need to take it out and try to inspect the engine heads where you installed your spark plug. You also need to check the ignition wires with the compression.

The next thing to do is to get some anti-seize to the threading of the plugs. Then, you need to install the new plugs into the engine. You also need to test the engine to ensure that it starts up and smoothly runs when you take it out for a drive.

How Much Does It Cost to Fix a Blown Out Spark Plug?

In general, the whole process of fixing a blown-out spark plug can cost a lot, and it’s due to the time-consuming process.

Thus, you can have your car fixed by a professional or a trained mechanic, costing around $500 to $1000. Of course, it can be a bit more or a bit less, depending on how much the mechanic charges you.

The costs of such a repair include the first insert, and it can cost less for the second and third ones if the rest of the holes need the same.

In short, you need to prepare for such a cost so you won’t get surprised if you ever get charged for it. 

How Do You Know If You Blew a Spark Plug?

An engine with a blown-out spark plug can suffer from several issues that are pretty noticeable. Thus, if you want to know if you blew a spark plug, you can check out these symptoms to confirm your thought.

Poor fuel efficiency

If you’re spending more fuel than before, then it should make you suspect problems with your spark plug. 

In general, your engine has to work harder if you have blown-out spark plugs. In other words, your car can’t burn the fuel effectively in the combustion chamber. 

As a result, you’ll see the effects of deteriorating plugs in your wallet when you pay more for gasoline.

Misfires of the engine

While an engine misfire happens for many reasons, one of these reasons is the spark plug. Misfires are frequently caused by at least one worn spark plug. 

You’ll notice that the engine’s speed slows down and then picks up again. As the engine fails and regains synchronization, you may hear it snap. 

When a car misfires, raw gasoline is released into the emissions, causing the catalytic converter to get damaged.

Check engine lights turned on.

Your check engine light goes on whenever there are problems, and spark plugs are one of them. So even if you neglect to bring your car in for regular maintenance, its algorithm is precisely designed to warn you of possible issues. 

Please take it as a rule of thumb to keep an eye out for the check engine light. It’s a forewarning signaling that it’s time to make a move.

Loud sounds from the engine

Noise is another noticeable thing to happen when your spark plug blows out. The noise will alert you if at least one of the spark plugs is failing.

It doesn’t matter what engine you have. Whether it’s a four, six, or eight-cylinder car, it will make noise when your spark plug blew.

When one cylinder’s efficiency is reduced, the others are overworked and unusual sounds, such as rattling, might result.

Acceleration struggles

If you find it challenging to accelerate or increase speed even when you step on the gas, you probably have a blown-out spark plug. A worn spark plug can no longer ignite the fuel-air combination in the combustor with the spark plug. 

When the car fails to accelerate correctly, this poor performance is among the most evident signs.


In a nutshell, spark plugs blow out for many reasons, and improper tightening and overuse are the primary causes. In addition, the spark plug may get threaded or galled. Or it can get damaged due to excessive heat and pressure. Whatever the reason is, you should know that a blown-out spark plug is a serious matter that you need to resolve soon. In most cases, you need to replace it.

Replacing the spark plugs is a straightforward procedure. It’s something that most individuals can learn to do on their own because it doesn’t take a lot of pricey tools or a lot of experience. However, you must be cautious when selecting the proper spark plugs and returning everything to its original location when you are completed.

If you know how to replace the spark plugs, you can do it on your own. However, if you think you can’t do it, it’s best to get an expert to fix it for you.

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Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more