Actually, gravity bleeding does work.. It's the Heinz Ketchup method ala Carly Simon's "Anticipation"...It takes some monitoring to keep the reservoir full and perhaps 30 minutes per wheel and not that much fluid. Once the cruddy old fluid is out of the line, I recycle it. It's a tried and true method I can't confirm it works on hydraulic clutches though. Power bleed on a clutch was my solution for that.