I actually tried that already. The noise is coming from the pump: I can hear the noise only with the climate control on (fron under the hood), and If I wiggle the pump the rpm's start oscillating even faster, which leads me to think its a bad pump. I would just replace it but at $250 for a dinky electric pump, I would like to know if that's the problem for sure. I was thinking there might be something else controlling the speed of the pump gone bad... maybe I'll check to see if there's a constant voltage going to the pump.