So I have a '07 F250 CC W/ 48k on the odo. I did what I consider to be a "simple" flush, and followed a tutorial on the YouTube by powerstrokehelp. After draining the Ford gold, I refilled with regular water and let it cycle for about 30 min with a short drive in that time frame. I then drained the water and let it cycle through the system with the plug out of the radiator and continuous water running through via the degas bottle. After all was out, I installed a sinister coolant filter and began to fill the system with CAT ELC. After approximately 10 qts of coolant, my system was full. I had the engine running to see if it would suck anymore in, but its to the fill line. Did I miss something other than using DI water in the simple flush process? Any help is appreiciated.