quail stacking cages

Ultimately, oil seals are devices that help to exclude dust and dirt, etc., while at all times retaining the lubricant in the piece of equipment. 

As type B with dust lip

Sealing of lip type seal is normally a result of an interference fit between the flexible sealing element, usually augmented by spring pressure and a shaft. Fluid retention is based on the precise amount of lip contact pressure. In most lip seals, increased fluid pressure in the sealed area causes lip contact pressure on the shaft to increase.

On some engines, you need to remove one or both manifolds (See Exhaust manifold gasket replacement ) to reach the crankcase side cover.

Power Steering Oil Seal:

Early engines used O-rings (also called packing rings or toric joints) as seals (first patented in 1896). These are just mechanical gaskets in the shape of a torus (a circular ring--like a lifesaver), seated in a groove and compressed during assembly between two or more parts. It creates a seal at the interface. However, O-rings require a fluid film to lubricate them. They have limited usefulness in vacuum application and at extremes of temperature. The modern oil seal represents a significant improvement over the simple O-ring because it effectively seals in lubrication and prevents contamination from outside under a wide range of pressures and temperatures.