CVO 9/1/2012Obtain a loan free radiator pressure tester from the local auto parts stores such as Autozone, O'Reilly or PepBoys. Follow their instructions and pump it an adequate air pressure in lbs allowances on the radiator cap. Observe the leaks and perform the repair.
Note: do not OVER-PRESSURE than the pressure allowed in the radiator cap.
OCG 9/1/2012Here is whats happening, when you are driving the car the fluid is in motion due to the pump forcing the fluid through or around your engine therefore because it is in motion it does not seem to be leaking while you are driving the vehicle however when you stop your car all the fluid settles (gravity) and finds the least path of resistance and thats either a bad hose, water pumps piss hole (need new water pump) or worse from your engine block. An easy way to determine were the leak is to take a can of deodorant spray (powder type) and spray the area you think it might be leaking from and run then turn off the car and the fluid will be obvious when it comes in contact with the deodorant. good luck