Also known as a Rotary Shaft Seal, Shaft Seal, Lip Seal, Elastomeric Lip Seal or any variation of these. It is a simple device for excluding dust, dirt, water or any other contaminant whilst retaining lubricant in rotary shaft equipment. Generally, it has been developed as a means of protecting the bearings of rotating shafts.
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Common causes of oil seal failure
On engines that rotate anti clockwise (viewed from the front) the pulley bolt unscrews clockwise.
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Figure 14.1. Shaft seals (DuPont Dow Elastomers).


Replacing gaskets and oil seals
If the seal is being fitted to original equipment you may have some influence over the shaft and housing bore finish, but if you are replacing a worn seal you still need to take into account the condition of these 2 essential parts.
Over time, the seal lip(s) will wear a shallow groove into the shafting due to the pressure the seal imposes upon it. Visible scoring on the shaft indicates a genuine possibility that the seal will not perform as well as intended. The potential for lubricants leaking out and particulates working their way through the seal drastically increases when placed over a worn location.
Auto oil seal Features