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Oil can pass through filter media. Bypass valve closed.
What happen when a spin-on filter is removed from service and upon inspection it is noted that the filter has collapsed in on itself. Why? What has caused this condition? What causes oil filter collapse?
It Isn’t What You Think
The first thought might be that the filter has some type of manufacturing defect that has caused this problem. This is usually not the case. Lubrication systems are equipped with a bypass valve that is present in either the system or within the system’s oil filter. This bypass valve is not to be confused with the pressure regulating valve that controls system oil pressure. The pressure regulating valve opens to redirect oil flow back to the sump when system pressure begins to exceed the manufacturer’s specified ranges.
Oil Must Flow
Oil cannot pass through filter media. Bypass valve opens.
The bypass valve opens to allow oil to go around the filter when conditions make it difficult or impossible for it to pass through the filter media. Cold start-ups or a filter that has not been properly serviced are two common instances during which time it will become necessary for the oil to circumnavigate the filter. The opening of the bypass valve is necessary to prevent oil starvation.
An open bypass valve resulting from a cold start is usually a short term condition because the oil temperature quickly rises as the engine heats up.
Under Pressure
If the bypass valve fails to open, differential pressure may
increase to the point of filter collapse.
When the filter is improperly serviced, and becomes plugged, the filtering process can be negated until such time as a new filter is put into service. During this plugged condition, the bypass valve will continually open and close to allow oil to flow around the filter. If this occurs, the oil will not be properly cleaned by the filter. If the bypass valve fails to open, differential pressure may
increase to the point of filter collapse.
The oil filter collapse is a clear indicator that the lubrication system is not functioning properly and that maintenance may be required.
Check out all the maintenance parts available on NAPA Online or trust one of our 16,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on oil filter collapse, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.
