Rick's Free Auto Repair Advice

Remove a stuck spark plug

How to remove a stuck spark plug

With longer spark plug life it’s not uncommon to run into a stuck spark plug. But if you exert mega force to remove a stuck spark plug, you can also shear off the threads in the aluminum cylinder head, and that’s a MAJOR repair. Removing a stuck spark plug without damaging the cylinder head takes time and patience. Screw this up and you’ll be in a world of hurt with a repair bill upwards of $500 to $1,200. To take it SLOWLY and follow these step by step directions to remove a stuck spark plug.

Buy a high quality rust penetrating oil

Most of you think WD-40 is a penetrating oil. It isn’t. It’s a general purpose lubricant and it’s a marginal rust penetrant in my opinion. If you’re serious about removing a stuck spark plug without damage, buy a real high quality rust penetrating oil like any one of these: PB Blaster, Liquid Wrench, Knock’er Loose and Freeze-off. Find those products at any home center or auto parts store.

remove stuck spark plug

Start by soaking

Blow out any dust or dirt around the spark plug (you don’t want it binding the threads or falling into the cylinder later of). Then shoot a liberal spray around the base of the spark plug. Wait at least 30-mins before trying to turn the spark plug.

Then try a quarter turn

Don’t think a 30-min soaking is going to let you zip the spark plug right out of the head. It won’t. But it will let you move the plug 1/8 to ¼ turn, and that’s what you want. Place the spark plug socket on the plug and try to turn it out by ¼ turn. If it still won’t budge, try tightening it ¼ turn. The whole point of this exercise is to move the threads enough so the rust penetrant can wick into the threads. Once the plug turns, add more rust penetrating oil. Continue turning until you meet resistance. Then STOP and add more penetrating oil.


I know this doesn’t make sense, but tighten the spark plug until it seats. Add more penetrating oil.

Loosen again until you meet resistance

Add more penetrating oil.

Repeat the tighten/loosen/penetrating oil step until the plug comes out

Clean the spark plug threads in the cylinder to remove as much rust penetrant as possible. Use a dry rag to soak up the oil. Then spray the seat and threads with brake cleaner to remove all traces of the oil.

Blow dry with compressed air

Install the new spark plug

Then install the new spark plug. Do NOT coat the threads with anti-seize unless the spark plug manufacturer specifically recommends it. Also, use a torque wrench to obtain the correct torque.


©, 2019 Rick Muscoplat


Posted on by Rick Muscoplat

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