My 54 two ton started heating one day. I flushed and refilled like always, was same. Drained and flushed again, always clear. Finally took rad out to shop. He has a water and pressure set-up to blow out crud. He put it on bottom hose connection and filled, pressurized and blew out all kinds of reddish rusty crud. Did once more. Tested for leaks, none, gave back, I installed, was good after that. By the way, as I removed from truck, the lower rad hose was full of rusty crud, even though the drain just let out clean anti-freeze. Pretty odd deal!
