hi i must admit i'm using just a regular red coolant from Toyota don't need antifreeze here in Aruba!!both of my top and lower hose seems to get quite hard once warmed upper one warms first tough, ever since i installed the dual radiator it only overflowed once, never did it again its like its no working checked bottle hose and they seem fine not blocked! i did some hard driving yesterday but i only manage to get it overheat and the over flow bottle stays the same as soon i let go of the gas it cools it self back again but fan stays on!