Had a little emergency with the wifemobile. She was a few miles away and her '09 Journey overheated. There is a small hole in the top of the overflow blowing off steam. I filled it with water and it ran fine at normal temp to get it home. It blew off most of the water I added in just a short drive though. I know that not being able to hold pressure will lower the boiling point and make it steam off that much quicker. Just wondering if that hole alone is likely the problem?