As part of routine maintenance on any motor vehicle, you need to regularly replace the spark plugs. Occasionally, when you go to remove a spark plug you will find that it is stuck, or seized. Removing a seized spark plug can be frustrating and time-consuming. However, it can be accomplished with a little elbow grease and a lot of patience.
Find the exact positioning of the spark plugs on your engine. Many vehicles have spark plugs in places that are extremely hard to get to, such as the bottom or side of the engine. In such cases you might need to use a lift to access them.
Pull the cap of the spark plug wire off the spark plug.
Spray penetrating oil down the barrel of the spark plug so the oil creates a good coating around the plug. The penetrating oil should help loosen any build-up and rust that are causing the spark plug to seize.
Wait at least 10 minutes to a half hour. This will give the oil time to penetrate the build-up around the spark plug. The longer you wait the better. Most mechanics recommend leaving the penetrating oil overnight.
Give the end of the seized spark plug a gentle tap.
Turn the spark plug to tighten it slightly before attempting to remove it. Use a wrench to turn the plug clockwise. Then, turn it counterclockwise to remove it. Slightly tightening the plug can help loosen the build-up around its threads.
Soak the spark plug with oil again if it is still stuck.
Turn on the vehicle's engine and allow it to warm up. The heat will aid in loosening the gunk around the plug, allowing the oil to get deeper into the spark plug's thread.
Allow the engine to cool, so as not to put yourself at risk of a burn injury.
Repeat Steps 1 through 4 until the seized spark plug comes loose.
When replacing a seized spark plug, it might be a good idea to coat the thread of the new spark plug with a high-heat resistant lubricant.
Never force a seized spark plug. Doing so could damage the engine.