ムサシニュース
This oil seal is used on the pulley side of the engine block to prevent leaks of engine oil inside the crank case and also prevents foreign substances from penetrating from the outside.
For engines equipped with a timing chain, engine oil also circulates in the chain mechanism on the outside of the engine block, timing gear case (cover) oil seal plays the same role.
For engines equipped with a timing belt, as the timing belt is removed for replacement, camshaft seals also are very often replaced at the same time together with crank shaft seals.
Since the temperature inside of engine block becomes extremely high, heat-resistant material is used.