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Mahle offers advice on leaky filters

Mahle, one of the world’s largest component manufacturers and vehicle systems suppliers, is dedicated to assisting technicians in expanding their knowledge on warranties when it comes to component installation and fault diagnoses. Filtration is a core competence for Mahle, therefore it is able to highlight a multitude of fitting problems that occur through inspection of the vehicle or installation of the replacement components.


In applications with spin-on oil filters, which Mahle designates with a part number beginning OC, leakage from the filter or oil loss from the filter’s screw-on flange may occur due to a clogged control valve in the oil pump.

This can be easily seen by technicians when the seal has become dislodged or the filter housing has expanded, which in some cases bursts the housing. The reason for this can typically be attributed to deposits and carbonised residue in the engine oil that are swept through the oil pump, where it causes sporadic clogging of the control valve.

Since the oil pressure is no longer adequately regulated or may even cease to be regulated altogether, extreme pressure peaks of more than 30 bar may occur as a result. The oil filter is unable to compensate for this tremendous rise in pressure and subsequently deforms.

The seal may also become dislodged or the end cap may bulge significantly, giving rise to insufficient contact pressure between the seal and the filter. As a result, oil is lost directly from the screw-on flange or the filter bursts, in which case the entire end cap detaches from the housing. However, in this scenario it is not enough to replace the filter, the technician must inspect and flush the entire oil circuit to remove all deposits and may even need to replace the oil pump with an integrated regulating valve.