What's the
downside to so-called "long-life" spark plugs? |
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? -- Vic
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.
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