I have a 2001 Ford Taurus that leaks coolant when driving. The car can be idling, and I can rev the engine, but it won't leak coolant then. Only when I'm driving. The coolant hits some hot part of the car causing it to steam very badly. I did a radiator pressure test and it was holding pressure and no coolant was leaking. I replaced the coolant reservoir and water pump but that didn't fix the problem. I don't believe it is the heater core because there is no coolant in the passenger side. Any clues on what this may be?