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

I’m trying to change my own spark plugs for the first time and I’m a little lost. I’ve heard that I should wait until the engine is “cold” to change them, but I’ve also heard I should do it while it’s hot. I’m not sure which is true. Can I change my spark plugs while the engine is hot?

Patrick Price · Answered on Mar 25, 2022
Reviewed by Shannon Martin, Licensed Insurance Agent.
Great question! Changing your own spark plugs is a great step toward handing your vehicle maintenance! I’m not sure who would have told you to change your spark plugs while the engine is hot, but I wouldn’t recommend taking any car advice from them in the future. The simple answer is no—you should not change spark plugs while the engine is hot.
The spark plug and the head it plugs into will expand and contract as they heat up and cool down. Since they are made of different materials, they won’t expand or contract at the same rate.
If you install spark plugs while the engine is hot, they will not fit properly. The best-case scenario is you have a spark plug that simply isn’t properly installed and does not work correctly. The worst-case scenario is that the plug isn’t in properly, and you’ve damaged the spark plug and/or the head.
You’ll want to wait at least 30 minutes before installing new spark plugs. That should give the engine adequate time to cool down.
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