Why Do Some Oil Seals Repeatedly Damage And Leak Oil?

 There are many high-speed rotating shaft parts in automobiles, such as crankshafts, camshafts, and half shafts. There are also shafts that move axially at low speeds, such as valves. These shafts need a lot of oil to lubricate when they are running, and these oils must be sealed in the engine or gearbox so that they cannot leak out. This requires a very important part-Oil Seal.

The oil seal is a mechanical component used to seal grease. It is often used in the bearings of various machines. Its function is to isolate the parts that need to be lubricated from the outside world and prevent the lubricant from leaking. It has the function of sealing internal oil and external dust. The current oil seal materials are mainly various rubbers. Such as: nitrile rubber, acrylic rubber, polyurethane rubber, silicone rubber, fluorine rubber and polytetrafluoroethylene rubber. The typical structure of the oil seal is shown in the figure below. It has the advantages of simple structure, light weight, small installation location, and easy processing.

Oil Seal

Under normal circumstances, the seal of this oil seal is very reliable, but many cars have oil leakage failures during use. The main factors leading to the deterioration of oil seal performance are as follows:

1.The oil seal rubber is aging, the elasticity is weakened, and the sealing force is reduced. This is the main factor for most Automobile Oil Seal oil leakage, because the oil seal is a rubber part and has to withstand high temperatures, and will age after a few years of use. For example, valve oil seal leakage is mainly caused by the aging of the oil seal. This point is mainly related to the material of the oil seal. If the material is better, the use time will be longer.

2. The bearing is worn or the shaft is bent and deformed, causing large radial runout and oil leakage. The oil leakage of the half-shaft oil seals of general models is caused by this reason. This is also the fundamental reason why some cars still leak oil after repeatedly replacing the half-shaft oil seals. In some models, the engine crankshaft is bent and deformed, and the front and rear oil seals of the crankshaft often leak oil. These require careful inspection and testing during the repair process.

3. If the shaft and oil seal are used for a long time, there will be a certain amount of wear, even a groove is ground on the shaft, and the gap between the two becomes larger and oil leaks.

4. Installation factors. When installing the oil seal, special tools are generally used. After the installation is in place, the edge of the oil seal is intact and the skeleton is not deformed. Some repairers use a screwdriver to trim the edge of the oil seal when installing the oil seal, which can easily cause the edge to deform.

5. Too much lubricating oil is added or the air vent is blocked. Whether it is engine oil or transmission oil, it must be added in accordance with the standard filling amount. If too much lubricating oil is added, it will cause excessive internal pressure, which will exceed the sealing pressure of the High Pressure Oil Seal and cause oil leakage. If the engine crankcase is not well ventilated or the transmission vent is blocked, it will also cause excessive internal pressure and oil leakage.

6. Whether the lubricating oil is compatible with the oil seal. Different oils in cars have different effects on rubber. Some oils have a swelling effect on the rubber, which will make the oil seal larger and make the seal more reliable; while some oils have a shrinking effect on the rubber, which will make the oil seal smaller and make the seal worse. Therefore, the oil on the car should not be added randomly or mixed, and the oil seal should also be used for special purposes. Otherwise, the seal will be unreliable.