Abstract: A system for liquid cleaning a plurality of dirty open-ended cylindrical internal combustion engine paper air filters by subjecting each filter to a cleaning cycle including successive first, intermediate and final cleaning steps. For each step liquid is pumped from a separate tank to spray heads for rinsing a filter at a cleaning station and effluent with entrained contaminants is collected for transfer away from the cleaning station. First step cleaning pumps an unclean liquid previously collected in a first tank as effluent from the intermediate step of a preceding filter cleaning cycle and first step effluent is disposed of away from the system. Intermediate step cleaning pumps a semi-clean liquid previously collected in a second tank as effluent from the final cleaning step of a preceding filter cleaning cycle and intermediate step effluent is collected and transferred as unclean liquid to the first tank for cleaning use during the first stage of the succeeding filter cleaning cycle.