REAR MAIN OIL SEALS
One of the factors that can cause leakage from the rear crankshaft seal is using the wrong type of engine oil, i.e. the incorrect viscosity. When too thin, the oil escapes the tight clearances of the bearings more easily which leads to a drop in system pressure. The inner lip that drives on the crankshaft will dry off and become stiff, unable to seal the crankshaft.
If the engine main bearing is worn beyond tolerance, the crankshaft will move inside the bearing cap. This will lead to stretching and moving of the rear crankshaft seal while the engine is running. This, of course, will prevent the seal from sealing properly.
The rear seal lip rides directly on the crankshaft, therefore the crankshaft surface is critical. Any wear or imperfections on the crankshaft can result in a leaking seal.
As the rear crankshaft seal inner lip rides on the shaft, when there is too much pressure from the crankcase, it will drag the seal onto the crankshaft and eventually cause it to swell, resulting in an oil leak.
A clogged or defective positive crankcase ventilation (PVC) system will increase the crankcase pressure and may result in pushing out the seal.
Also, in a turbocharged or supercharged engine, excessive engine blow-by, due to defective or worn-out piston rings, can increase the crankcase pressure, affecting the seals and resulting in oil leaks.
On an automatic transmission, check the flex plate. On a manual transmission, check the input shaft. Problems with either can stress the rear crankshaft oil seal.
Some rear crankshaft oil seals have a polytetrafluoroethylene coating that is designed to be installed dry. The seal will transmit a PTFE layer to the crankshaft that the inner lip of the seal will sit on. The PTFE will prevent wear and seals better than Viton or silicone material. If the seal is coated with oil during installation, it will cause leakage.
Our oil seals are manufactured according to OE specification and will retain lubricants inside the engine, keep contaminants out under normal operating conditions.
For the various reasons mentioned above, which are not related to the manufacture of our seals, the Company is unable to guarantee such.