2019 NAPA Reference Guide

TECHNICAL SERVICE BULLETIN 83-1 Over Pressurized Lube Oil Filters Revised May 2013 Page 2 of 4 Figure 2 shows the system operating with the regulating valve stuck in the closed position. Under these conditions the pressure builds up equally on all components in the system until something happens to relieve the pressure. If the regulating valve becomes unstuck, the pressure will return to normal. Normal operating pressure causes no permanent deformation of the filter body. When the system pressure reaches 150 PSI (1,000 kPa) due to a faulty regulating valve, most filters become permanently deformed. At this pressure the gasket usually will not blow out and the lockseam will remain sound. If the regulating valve still remains stuck, the pressure will increase further and the gasket between the filter and the base can be blown out. This will probably cause the loss of all the oil in the system. If the filter has been installed on the tight side, the gasket may not blow out and the lockseam will unwind as the pressure continues to rise. The main point is that the deformed filter is not the cause of this excessive pressure, but is the victim of a faulty regulating valve. If the customer is alert and shuts the engine off at the first sign of trouble (red light on or reduced oil pressure) they can limit their loss to a tow job, oil change, new filter and oil pressure regulating valve inspection. If the vehicle continues to be driven, engine failure is probable. The customer may ask if a plugged filter could have caused the over pressurized condition. The answer is no; if the regulating valve is functioning properly it will maintain the pressure on the filter at 40 PSI (280 kPa) or 60 PSI (410 kPa) even if the filter is plugged. In summary, if a lube filter distorts due to excessive pressure in the system, the fault lies with the oil pump pressure regulating valve and not with the filter. 1083