How Long To Let Engine Cool Before Changing Spark Plugs?

Spark plugs are critical components in every gasoline-powered engines. Without them, your car will not start. They provide the spark needed to ignite the air-fuel mixture in the combustion chamber required for the vehicle to start. However, they can become fouled or damaged over time, needing replacement.

One of the common contemplation car owners have when planning on replacing old plugs is how long to let engine cool before changing spark plugs. Read on if you want to be sure whether your engine should become cool or not before changing the spark plugs.

how long should you wait to change spark plugs

How long to Let the Engine Cool Before Changing Spark Plugs?

While spark plugs are engineered for long-term durability, they need to be changed between 30,000 to 50,000 miles. However, this is an average replacement interval. Your spark plug brand may last longer or shorter.

When replacing spark plugs, you will notice that other engine parts will cool down, but the spark plug is still hot. This is because the spark plug is in an enclosed location, and it is what generates the spark needed for combustion.

I don’t know anyone who would want to change spark plugs while the engine is hot, and even if there are, do not take advice from such persons in the future.

Always let your engine cool down for at least 30 minutes before losing the spark plugs. It is necessary to allow the engine to cool down before changing the spark plugs. The engine must not be completely cooled. At best, it should be warm and not hot.

If you are wondering, how long does it take for an engine to cool down? It takes 30 minutes to an hour, depending on the engine model.

If the engine is warm or cooled, you can hold the spark plug without burning off your hand. But if it is hot, the car’s torque specifications may be altered. However, there may be no consequences in most cases, but it’s better to be safe than sorry.

best temperature to change spark plugs

Frequently Asked Questions – FAQs

Q: Is it ok to change spark plugs while the engine is hot?

The short answer is no. It is not okay to change spark plugs when the engine is still hot. The head cylinder, where the spark plug threads into and the plugs, will expand and contrast as the engine get hot and cool down.

Since the head cylinder and the plugs are not made of the same materials, they’ll not expand and contrast at the same rate. Therefore, if you replace plugs while the engine is still hot, they may not fit in properly. There are two possible outcomes. The first is that the plug may not tighten properly or work correctly. The second is that changing spark plugs on warm engine could damage the cylinder head thread.

Q: Does the engine need to be cold to change the spark plugs?

As explained earlier, materials have different expanding and contrasting rates. You don’t want to be torquing anything when hot, including bolts, nuts, and spark plugs.

If you are like one of my friends, Liam, replace the spark plugs as soon as you have them. But if you pay attention to details and are more reasonable, allow the engine to cool before changing the spark plugs.

Car engines need to be cooled before changing spark plugs, especially engines with aluminum heads. Aluminum loses strength at high temperatures, and replacing the plugs when hot may cause you to strip the plug threads. So, if you are wondering – can you change your spark plugs while engine is hot, the answer is you shouldn’t change plugs on a hot engine.

Q: Should you remove spark plugs warm or cold?

There’s nothing wrong with changing spark plugs when the engine is warm. Similarly, changing spark plugs in cold weather is okay. In short, cold weather is the best temperature to change spark plugs.

If you are looking for the best temperature to change your spark plugs, allow the engine to be dead-cooled. Kindly note that you can only risk causing issues by changing sparks on a hot engine. Both warm and cold are acceptable temperatures for plug replacement.

Q: Does car run better after spark plug change?

In most cases, there will be an increase in horsepower and overall engine performance after changing the spark plugs and wires. You will notice an increase in acceleration, and the engine will run smoother and faster. You may also have an increase in fuel economy.

As the spark plug gets old and closer to its shelf life, it’ll affect the engine performance. Replacing old spark plugs doesn’t necessarily increase horsepower; it only restores the lost power. In other words, installing performance spark plugs only restores the engine to its default horsepower and overall engine performance.

Hot Or Cold? Spark Plug Installation Temperature YouTube Video

Final Words

How long to let engine cool down before changing spark plugs doesn’t matter if you have an iron engine because the expanding and contrasting rate of the engine and plugs when hot and cool will be the same. However, if you have a newer engine built with aluminum, allow the engine to cool for 30 minutes before changing the spark plugs.

If you are also wondering how long to let engine cool before changing oil, let the engine cool for at least 30 minutes before draining the engine. In terms of oil, wait 30 minutes whether you have an iron or aluminum engine block.


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