Extracting broken spark plug shell from engine: urgent

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Old 01-16-21, 06:57 PM
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Extracting broken spark plug shell from engine: urgent

2013 Subaru Legacy, 2.5L, 4 Cylinders, CVT. My son over torqued the spark plug when replacing spark plug. As a result, the metal thread portion broke and stuck in the spark plug hole. As you can see in the picture, the one on the left is good one and the one on the right is broken one. Does anyone have any suggestion of taking it out other than take the head off the engine? Thanks in advance!
 
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Old 01-16-21, 07:09 PM
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My first thought, gingerly because you don't want to make things worse, is a broken bolt extractor. Definitely not my first choice in most cases, but being new threads, with no heat or corrosion yet in play, I'm pretty sure that's where I would start.
 
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Old 01-16-21, 07:19 PM
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Soak the threads for an hour with penetrating oil or WD-40.
Use dry ice to chill the threaded core so it contracts.
Get a 'Tap-Out' bit,
If you don't have an impact wrench, you'll need a breaker bar, a 2' section of pipe, and a 2x4.

Slide the pipe over the breaker bar for leverage, snug up the Tap-Out, and use the 2x4 to whack the end of the pipe like you're hitting a grand slam. You need t to break ALL of the threads free in one shot.
If you apply force slowly, the Tap-Out expands the threaded core and pushes it tighter into the block so it binds and sticks. One sharp whack will break the threads free, then you then should be able to remove the threaded core easily.
 

Last edited by Hal_S; 01-16-21 at 09:16 PM.
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Old 01-16-21, 07:22 PM
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More than likely..... the threaded portion will not be bound in the head.
You'll need to use bolt extractor. You won't need to drill which can be the difficult part.

The video shows how to use one. You can get them at auto parts stores.
Extractor video

Just thinking to myself...... you may not even need an extractor. Dig thru your supply of screwdrivers. Try to find one with a tapered head like in the picture. You want to find one that just fits into the broken spark plug. Push it into the shell and see if it turns. If the screwdriver slips..... give it a gentle tap. If it still slips you'll need an extractor.
 
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Old 01-16-21, 07:43 PM
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And remember that any filings you make will be in the cylinder, scoring the piston walls. Might want to make generous use of a magnet extension to pick up any stray bits that fall into the cylinder.
 
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Old 01-16-21, 07:50 PM
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An Ease Out extractor was my first thought as well.

In all my time, I dont think I have EVER seen that happen.

Get Jr a torque wrench for his birthday
 
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Old 01-16-21, 08:29 PM
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Originally Posted by XSleeper
And remember that any filings you make will be in the cylinder, scoring the piston walls.
Before you start, block the spark plug hole with a cotton ball or tampon to keep metal bits from falling into the cylinder.
 
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Old 01-16-21, 09:08 PM
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Not proud to admit it, but i've done this too. Fortunately it stays with you as a "how not to do it" lesson. The Easy Out in post #3 from Hal_S worked for me.

Dave O
 
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Old 01-17-21, 05:49 PM
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Thanks all. I bought a set of screw extractor like Hal_S mentioned above and just use hand to take it off. I am lucky that the broken spark plug is new and I didn't even use penetrating oil. Thanks again.
 
 

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