DIFFERENTIAL GP 2878223 - Caterpillar

Do not use a thread tap. A thread tap will remove metal unnecessarily. The threads could be stripped and the cylinder head could be damaged.
Inspecting the Spark Plug
Inspect the spark plug closely for damage. The condition of the spark plug can indicate the operating condition of the engine.
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(1) Terminal post (2) Insulator (3) Shell (4) Gasket (5) ElectrodeTerminal post (1) must not move. If the terminal post can be moved by hand, carefully tighten the post into the threads of the insulator. If the post cannot be tightened, discard the spark plug.Inspect insulator (2) for cracks. If a crack is found, discard the spark plug.Faint marks may extend from shell (3) onto the insulator. The marks may be a result of corona that forms at the top of the shell. The conductor will develop a corona when a high voltage potential ionizes the air. This corona is a normal condition. This corona is not an indication of leakage between the shell and the insulator.Inspect shell (3) for damage. Cracks can be caused by overtightening the spark plug. Overtightening can also yield the metal which loosens the shell. Discard any spark plug that has a shell that is cracked or loose.
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(6) Precious metal tips on the electrode and the ground strapCat spark plugs have precious metal tips (6) on the electrode and the ground strap. This material will gradually erode. Use extreme care when you set the electrode gap. Maintain even spacing and proper alignment between the two precious metal surfaces.Replace the spark plug if the precious metal is worn off.A light brown deposit or a beige deposit around the electrode is produced by normal operation.Deposits that are gray or black may be caused by the following substances:
Excessive oil
Use of the wrong oil
A substance that is introduced through the fuel system or the air system
Poor combustion because of a rich air/fuel mixtureA spark plug can operate despite a buildup of ash. However, a buildup of ash can cover the electrode gap. This condition may cause a misfire. Large deposits may retain heat which can cause premature fuel ignition. This condition can lead to uncontrollable detonation.Cleaning the Spark Plug
Thoroughly clean the spark plug. Do not use a wire brush. Glass beads are the preferred method for cleaning.Follow these guidelines for using glass beads:
Always use clean glass beads.
Only use glass beads on the electrode and the insulator near the electrode.
Do not use glass beads on any other area of the spark plug.
Clean the rest of the spark plug with nonflammable solvent.Installing the Spark Plug
Note: Use the 9U-7516 Spark Plug Gauge to measure the electrode gap. Do not use a flat feeler gauge for measuring the electrode gap of used spark plugs. A feeler gauge will incorrectly measure the actual electrode gap because the used precious metal tips are curved.
Before installing the spark plug, set the electrode gap according to the engine Specifications manual.Adjust the electrode gap, if necessary. Bend the ground strap at the existing bend. Then bend the