I just got a mishimoto rad and I think I have a very slight leak at the overflow tube. It looks like it screws in to the rad neck and is leaking a very small amount from the threaded area....but the area is blocked by the cap when the cap is on. Also I am leaving the cap off overnight and in the morning the level is down about an inch...air is finding it's way out every night and causing the level to drop. I keep topping it off and the driving it....each time the upper hose feels pressurized and it takes more coolant