Upper hose is collapsing!

The motor supposedly has only had about 700 miles put on it since 2002 so it very well could be full of crud. "One man's project not done right is another man's nightmare & a mistake is his wife's eyes". I am going to pull the thermostat & leave it out, it sounds like I really do not need it especially living in the south. Then I am going to drain the rad, disconnect all the hoses & do whatever I can to flush out the motor. I will do some research on the rad cap pressure but I have seen guys on here running caps as low as 7 lbs. I just have never seen an upper hose sucked in before, something is creating a bunch of vacuum when the motor is shut off & cooling down. I just thought I would see if anyone else had ever had this issue because like most things there could be various causes & I hate just guessing. The flush should not be very costly so it is a good starting point. Thanks guys. Let me know if anyone has anymore ideas & I will post results as I try things. It is just about time to give up on this motor & start building one of my own.