probably cavitating, I noticed on mine that with the fluxuation in fluid level from the ram moving that the stock reservoir wasnt holding enough fluid while running causing
slight cavitation but overflows if shut off. Got this reservoir from speedway motors P/N 91032876-STD-10. Also running a cooler.
http://www.speedwaymotors.com/xq/aspx/display_id.2062/qx/Product.htm
