The t-stat is the most likely cause when running. They are bad about just comming apart. With the engine cold, remove the three bolts and remove the t-stat cover. Remove the O-ring with a pick and the t-stat will lift up easily in your hand. Replace it then, it is inexpensive insurance. If the t-stat cover is plastic, replace it with a metal one. And be VERY careful with the upper radiator connection. Very good chance of breakage. You can see if the neck has been upgraded with a metal sleeve inside of the neck. If not, check carefully for cracks. If present, have a radiator shop replace that the side tank with an updated one. $200.
If your hoses collapse after a cool down, the radiator cap is not venting and needs replacing.
Have fun and stay cool,