Can anyone clarify these vague skid steer servicing manual instructions:" Connect a vacuum pump to hydraulic tank filler spout before removing main control valve for servicing"? If I were to speculate,I imagine ,drawing a vacuum at the tank could draw back any hydraulic fluid and reduce a leaking mess caused by the disconnected hydraulic hoses and later after replacing the valve a vacuum may help eliminate any entrapped air. Enough speculation on my part. Can anyone explain the specifics of that recommended service procedure ? ,Thanks