Radiator upper hose Question

[kakarot]

Help I'm trying to solved this issue since I replace a new RAD and both hoses. The upper hose seem to collapsed or flat(I don't know the term for this issue) if I loose the RAD cap off, the upper hose will pop up to normal again. It seem like something is sucking the air on the upper hose. The only way to get the upper hose back to it original shape is to loosing the rad cap and it will pop up like there is some air trapping. Bottom hose is fine temp is fine.

My car is a 1998 4runner v6 4x4

 

[kakarot]

Guys I think I found the solution for collapsed upper RAD hose.
The solution is a new RAD cap that all it was. It also could be clog overflow reservoir tube just want to throw it out there in case someone is having the same issue as I am.