I was flushing the coolant on my 6.0 when I added straight water to the system for the second time I drove up the road bout 2 miles when I heard a whistling sound coming from my coolant tank then a this sound when I lifted the hood the water level was ok and not boiling the whistle stopped as soon as I heard the thud. When I pulled the bottom hose off the radiator side of the water was just warm but the block side was quite a bit hotter. Did I do damage? I just had heads done with arp studs. Input please.