Volvo Penta crankcase filters. The crankcase breather performs the extremely important function of equalizing the pressure in the crankcase during differtent operational phases of the engine. At times, air needs to be released from and at the other times, to be sucked into the crankcase. The crankcase filter is manufactured in accordance with the same exacting standards as Volvo Penta air filters. The crankcase filter should be replaced at least once a year.