High Oil Consumption
NOTE:
Piston type vacuum pumps require some oil for piston and cylinder wall lubrication and oil traces do not indicate a defective pump. Sudden increase in oil consumption may indicate a defective pump.
To test for excessive oil consumption, install a 2" glass blown type fuel filter (with filter element removed) in vacuum pump outlet line. An accumulation of 1/4" of oil in the bowl after 25 miles of operation indicates a defective pump.