Thanks for the kudos
And just to fill in some gaps.
If upper rad hose collapses as engine cools off then "center valve" in rad cap is bad or overflow tank/hose is plugged up, this can happen if you get debris in the tank, coolant can come in, it pushes debris out of the way, but it can't get back out to rad because debris settles at the bottom and plugs the hole, you end up with negative pressure in cooling system(below outside air pressure) and 15psi outside air pressure collapses hose.
Pressure in the cooling system is to raise the boiling point of the fluid.
Water boils at 212degF
50/50 coolant/water boils at 220degF
Each 1 psi of pressure raises boiling point by appox. 3degF
So a 15psi cap adds 45degF to boiling point of any fluid, for 50/50 that would make boiling point 265degF(220 + 45)
Outside air pressure is 15psi at sea level, at 4,000ft it is 13psi, so you LOSE 6degF in the boiling point if driving at 4,000ft, keep that in mind.
Engine design can have issues, "hot spots" can develop near the cylinders domes in the heads, manufacturers usually have a rad cap pressure recommendation, you should use this even if it seems high, if engine does have a hot spot coolant can "flash" to steam if pressure is too low, if that happens usually a hose will blow off, or overflow tank will...........overflow, lol, as higher steam volume forces out the coolant.
Some vehicles use an "expansion tank" instead of an overflow tank, the difference is the expansion tank has a "rad cap" and is not open to the air.
The expansion tank has some air in it that compresses as coolant volume increases from heat, rad cap on these just has the one valve, for rated pressure of system.