This oil seal prevents lubricant leakage from the crankshaft housing and blocks contaminants from entering the engine's rotating assembly. It sits in the bore at the front or rear of the crankshaft, where the seal lip rides on the shaft journal to maintain a fluid-tight barrier. A worn or hardened seal allows oil to weep past the lip, leading to low oil pressure and potential contamination of the clutch or belt drive surfaces. The seal is manufactured to the original bore and shaft tolerances, so no shimming or adapter is required for installation. On reinstall, inspect the shaft surface for grooves and apply a thin film of oil to the seal lip before seating it flush with the housing face.