Grease seals prevent liquid grease from escaping from automobile wheel bearing assemblies. They consist of a soft rubber or nylon ring embedded in a metal housing. Leather seals were used in early automobiles, but rubber seals are now preferred. It is important to replace seals when installing new wheel bearings, as a faulty seal can cause grease to leak out and damage the brakes. When replacing a seal, it is important to coat the inside lip with a light oil or grease to prevent distortion.
Grease seals are typically found on automobile wheel bearing assemblies. The automotive wheel bearing consists of an outer and an inner roller bearing together with grease seals. Roller bearings are filled with grease when they’re installed, and that grease melts away as the wheel spins. Grease seals consist of a soft rubber or nylon ring embedded in a metal housing that is installed in the axle housing or wheel hub and is placed close to the axle or spindle. Since grease melts due to the friction of the wheel turning, grease seals prevent liquid grease from escaping from the bearing housing.
In the early years of the automobile, grease seals were formed from leather. Leather grease seals were adequate and successful due in part to the relatively slow speed of the wheels. As the automobile evolved and wheel speeds increased, leather grease seals proved inadequate. An improved version consisting of a rubber seal bonded to a metal body has been shown to successfully seal bearings, preventing grease from leaking out of the bearing assembly. Some vehicles manufactured before 1950 used a rope seal. http://www.wisegeek.com/back/article.htm?id=128806seals rope has had marginal success at sealing bearings.
When installing a new wheel bearing, it is recommended that people also replace the grease seals. The slightest nick or manipulation of the grease seal could result in a faulty seal and grease leaking out of the bearing. Signs of a bad seal are streaks of grease running from the center of the wheel to the outer edge of the wheel or tire. In the case of a bad inner seal, the smell of hot or burnt grease when braking is often a telltale sign of a problem. This happens when the leaking grease is leaked onto the brake rotor and is heated by the friction of applying the brakes.
Replacing a seal is as easy as pulling the failed seal out of its place and inserting the new seal into place. It is imperative that the inside lip of the new seal is coated with a light oil or grease before being installed on the axle or spindle. This prevents the gasket from overheating, resulting in gasket distortion. A distorted seal will not fit near the axle or spindle and will allow grease to escape from the bearing.
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