Oil pressure the cause of SPIN-ON filter damage
Filter manufacturers get sometimes claims based on spin-on filter damage due to effect of excessive oil pressure. Customer advices about gasket between filter and engine casing push out during exploitation or puncturing of a lock joining the can with the filter cover. In both cases the consequences are very serious. Due to sudden oil pressure drop in the system, the engine is exposed to seizure.
Upon the WIX-FILTRON experience it may be confirmed that customers holding damaged filter are certain about it being the reason of lubrication system failure. They don't hide their surprise and often indignation when the manufacturer's service upon checking the filter present unambiguous proof about the filter being efficient while the reason of failure was excessive oil pressure in the system.
So what was the cause of the failure?
Trying to understand the reasons of excessive pressure in the lubrication system, it is recommended to learn about functioning rules and structure of basic engine lubrication system elements.
Drawing no. 1 Diagram of a system with the spin-on filter installed in-line.
Oil is sucked through a pump from the oil sump and pumped through pipes into the filter and then run directly in the lubrication place of all cooperating engine parts.
The efficiency of the pump is higher than the engine requirements. Steady pressure is maintained by the overflow valve, usually placed in the pump corp, which opens at a designed pressure, draining the oil excess into the oil sump. For cars the required pressure is between 2.8 and 4.1 bar. It is necessary for effective lubrication of most loaded engine elements, protecting it from excessive wear. Oil filters are designed in such a way to easily withstand work loads. Only the pressure increase in the system may cause their damage.
What can cause lubrication system pressure increase?
Imperfect work of overflow valve which can be either blocked in a closed position or moves to the open position too slow may be the reason of pressure increase in the system after ignition.
Drawing no. 2 Diagram of the lubrication system with the overflow valve blocked.
Normal pressure does not cause permanent deformations of the filter corp, however the pressure increases up to about 10 bar, causing permanent deformation of a can in most spin-on filters. A further pressure increase when the filter wasn't tightened properly, leakage from the gasket or its push out from the seat in the cover may occur. If the filter was tightened properly during oil replacement, the gasket will not be pushed out but puncturing of a lock between the cover and filter casing may occur. In both cases a sudden oil leakage and pressure drop in the lubrication system occurs which makes further car exploitation impossible. Driving continuation in this situation endangers engine seizure.
To summarise, the reason for filter damage and oil leakage caused by excessive pressure increase is not the filter defect but incorrect operation of an overflow valve in the lubrication system.
Prepared on the basis of Filter Manufacturers Council – Technical Service Bulletin 83-1R2