Ideas for removing a spark plug that is stuck in place?

Dear Car Talk

Dear Car Talk | May 01, 1999

Dear Tom and Ray:

After my wife left her Mercury Tracer at the dealer for a tuneup, she received a call from the service manager. He said one of the spark plugs was stuck and could not be removed without the risk of breaking it. Did they teach you at MIT how to get a steel plug out of an aluminum cylinder head without causing expensive damage? --

TOM: No, we didn't learn that at MIT, Vic. We learned that the hard way -- twice -- on Rocco Cannoli's Coupe DeVille.

RAY: Here's the recommended technique. First, you spray the plug with penetrating oil and drive the car. Do this every day for a week or so to allow the oil to really,
what? Penetrate!

TOM: Then, when the engine is cold, you very gently try to work it out. You have to be careful not to force it, or you'll strip the hole and ruin the cylinder head.

RAY: Each time you make a little progress you spray on some more penetrating oil, and then work it some more. It could take hours to get it out, so be patient.

TOM: If you absolutely can't get it out, or -- the more likely scenario -- you break it while trying to get it out, then you have to have the plug "drilled out." Fortunately,
the plugs on this car are all within easy reach, so you don't have to remove the cylinder head to do it.

RAY: After you successfully drill out the old plug, you use a "HeliCoil" screw-thread insert to create a new set of threads, and then you're back in business.

TOM: We see this problem a lot on engines that have "long-life spark plugs" in them. After 60,000 or 100,000 miles, there's nothing wrong with the plugs, except that
they've, as Buddha would say, "become one" with the cylinder head. So even if you use long-life plugs or own one of those cars that calls for a tuneup every 100,000
miles, have your mechanic remove and reinstall the plugs every 30,000 miles or so just for kicks. At least that way you'll be able to get them out when you need to. Good
luck, Vic.


Don't get stuck with a lemon. Read Tom and Ray's guide How to Buy a Great Used Car: Things Detroit and Tokyo Don't Want You to Know. Send $3 and a stamped
(55 cents), self-addressed, No. 10 envelope to Used Car, PO Box 6420, Riverton, NJ 08077-6420.


?(C) 1999 by Tom and Ray Magliozzi and Doug Berman
Distributed by King Features Syndicate, Inc.

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