How to Safely Remove a Stuck Spark Plug

Step-by-Step Guide to Remove a Stuck Spark Plug

Starting in the 80’s, carmakers switched to precious metal-tipped spark plugs that last 2X to 4X longer than the older nickel-plated spark plugs. Removing those stuck spark plugs can feel like trying to pull the Excalibur from a stone. Over the years, I’ve faced my share of seized spark plugs, and I can tell you one thing with certainty: patience, the right tools, and a proper technique are your best allies. If you’re ready to tackle this challenge, let me walk you through the steps to safely remove a stuck spark plug without damaging your engine.

If you approach this job with brute force, you can break the porcelain, with portions falling into the cylinder, or shear off the cylinder head threads. Then you’re looking at a MAJOR repair.

This picture shows what happens if you use brute force to remove a stuck spark plug.

Photo Credit: MrTechnic

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 mediocre 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.

Start With A Cold Engine

1) Use compressed air to blow out any dust or dirt around the spark plug (you don’t want it binding the threads or falling into the cylinder later.

2) Shoot shoot a liberal spray of rust penetrant around the base of the spark plug. Wait at least 30-mins before trying to turn the spark plug.

3) Then try 1/8 turn and stop. Soak again with rust penetrant and tighten the plug. Then try unscrewing it by a 1/4 turn.

4) The whole point of this is to work the rust penenetrant into the cylinder head threads. So the technique I use is to loosen until I meet resistance, loosen a bit, soak with rust penetrant, and then tighten the plug. I repeat this over and over, unscrewing the plug a bit more each time.

Clean the Threads with Brake Cleaner

Once the plug is removed, squirt aerosol brake cleaner onto the spark plug threads and dry the area with compressed air. This is to prevent the rust penetrant from affecting final spark plug torque

Install the new spark plug and tighten to spec

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