finally flushed all the old coolant out of the truck after several hours. all i need to do now is add the coolant and distilled water. my question is this. the truck calls for 7 gallons of fluid. i have yet to get 7 gallons of distilled water in it when im flushing. usually at 3 gallons its coming out of the top of the degas bottle. i tried running it, thinking it needed to be burped. when i pulled it back in to check..the bottle was still full. why isn't this thing taking the 7 gallons that it calls for? any ideas?