Poor sealing of oil seals is the main factor causing oil leakage. When the shaft is worn and forms grooves, even if a new oil seal is replaced, it cannot be sealed. This is because the contact pressure between the oil seal lip and the shaft decreases, resulting in a small interference between the oil seal lip diameter and the shaft diameter after installation. Taking the crankshaft oil seal of S195 diesel engine as an example, the main reasons for its poor sealing are analyzed as follows:

① Poor manufacturing quality of oil seals;

② Poor quality of shaft or bearing;

③ Improper use and maintenance;

④ Improper installation;

⑤ Improper storage and adverse effects caused by environmental pollution.