1994 e320 spark plug problems - Mercedes-Benz Forum

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post #1 of 2 (permalink) Old 11-15-2009, 07:32 PM Thread Starter
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1994 e320 spark plug problems

I recently purchased a 1994 e320 with 150,000 miles on it that has a few quirks. The car was idling rough when I first saw it, but for $1800, I thought it could be worth fixing. Anyway, today I discovered that 2 of the spark plugs had shattered ceramic and when I pulled them they were blackened as well. I successfully replaced 5 of these NGK plugs and installed Bosch +4. The 6th plug has been a bit of a problem for me because the plug separated at the threads. The entire ceramic portion of the plug, along with the nut end that the socket fits onto, slipped right out of the threads. I am using a screw removal kit to try and get it out of there to no avail. I am starting to think that the spark plug threads might be fused into the aluminum cylinder head. I am not sure what to do next, because I was so close to solving this problem. I know I should probably remove the head and have a machine shop heli-coil it, but i want a quick fix that won't score the cylinder walls. Any advice would be appreciated.
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post #2 of 2 (permalink) Old 11-17-2009, 10:16 AM
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Have you heated it? If you're going to try it, stick the removal pin ready to turn with the plug. Heat the thread area (the aluminum will expand more than the steel) and turn the pin. Better yet, tap if you can for a left thread screw (if you can get screw and tap) and drive the screw, then apply heat, then try to turn the screw and drive the plug out.

Watch out with making a pyre, keep the heat localized, on dry and fuel-free surface. A low power electric soldering gun may be best.

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