If, because of the construction of the engine, the position of the spark plugs makes it difficult to fit or remove them (or even to see them), the plug wrench may tilt off-axis or slip. If the wrench slips and its inside wall strikes the ribbing on the plug’s insulator, or its terminal, the insulator may break.
- If the plug wrench slips and its inside wall strikes the insulator ribbing (see “1.” in the illustration), the insulator may be broken as shown in Photo 2. The location of the break may not be visible (inside the metal shell) as shown in Photo 3.
- Alternatively, if the inside wall of the plug wrench strikes the terminal (see “2.” in the illustration) the insulator may crack from the tip as shown in Photo 4.
Note:Since this kind of problem is most likely to occur with engines where fitting and removing spark plugs is difficult (where plug changes are accomplished by feeling by hand), you can prevent trouble by using a sturdy wrench and performing the operation carefully in such cases.
