The front crank seal is a ring of silicon or elastomer material that sits at the front end of the crankshaft and prevents oil from leaking out of the engine. The crank sits on several main bearings and the front seal sits between the final bearing and the timing cover.
The crank is located at the bottom of the engine block behind the timing chain cover. A gear or belt connects the crank to the cam of the motor. The timing chain cover must be removed to gain access to the mechanical oil crank seal in order to inspect it for damages.