Lesson 1/Learning Event 1
The lower part of the crankcase holds the oil and is called the oil pan. It is usually made of sheet metal and is
bolted to the bottom of the cylinder block. A gasket is used between the block and pan to prevent oil leaks. A
threaded plug in the bottom of the oil pan allows the lubricating oil to be drained without removing the pan.
The crankcase sometimes provides the mounting points that support the entire engine in the vehicle frame.
Rubber mounts are usually located between the crankcase brackets and vehicle frame. This is to insulate the
frame and body from engine vibrations and noise.
FIGURE 20. PISTON.
The pistons in use today are made of metal that is lightweight but very strong. The pistons must come to a
complete stop, and then start again in the opposite direction at the end of each stroke. Therefore, lightweight
pistons are desired because they take less power away from the engine. The pistons must be strong to
withstand the force created by the combustion of the fuel-air mixture.