try this
 

I need to know if a slight "flushing" or water sound is normal through the heater core.
I pressure tested my cooling system tonight and it is fine.
When you guys first start the car listen to see if you can hear the water flowing through the heater core or if you are at a stop light listen carefully to see if you can hear this noise when you start to excelerate slowly or even just rev the motor to 2k slowly. I can hear it in my car, but the radio and everything has to be off. Windows up, etc..
Let me know if you hear this.
If I wasnt really listening for it I might not hear it, but now that I now its there, I hear it all the time.
So you will really have to try to listen for it.