when it's whirling around from the turbulence the fan produces. When I thought the high pressure hose on mine was leaking it turned out that the fluid supply pipe was leaking where it bolts to the pump. The o-rings I suppose shrunk over time. Took me a couple pulls of the power steering pump to figure that out because oil gets everywhere. Replaced the o-rings and it's perfect now. That's not to say yours is the same, but don't rule it out.