Originally Posted by BruceK
"...the entire fresh water(closed)system of your engine is under suction from the fresh water circulation pump. It is critical that the molded hoses have spring inserts to prevent them from drawing shut when the engine is running"
If that were the case you could leave the "radiator cap" off and increase the temperature limit of your coolant. Or conversely, you could remove the cap while the engine is hot and running and not have a worry in the world about blowing hot coolant all over yourself and the engine room.
There is a pressure differential on either side of the pump, after all that is what a pump does, it creates a pressure differential to move fluid. But, once the engine warms up the entire system is well above atmospheric pressure. What we call "suction" and the force that collapses the hose is the difference between the pressure inside the hose and where you are standing to look at it.
The flow of coolant in your engine is from the header tank to the heat exchanger, to the manifold, then on to the suction side of the fresh water pump. Unless you have a serious flow restriction in the heat exchanger there is no way the pressure between the heat exchanger and the manifold can go below atmospheric when that engine is hot. If it did your coolant would flash into steam at reduced pressure, most likely at the pump itself and all the pressure differential would vanish.
I believe that you will find that you simply have a well sealed fresh water circuit and when the engine cools a slight vacuum is formed in the system. I bet that if you remove your radiator cap when the engine has cooled enough to do it safely and leave it loose you will probably not see a collapsed hose.
Does your radiator cap have a vacuum breaker or overflow tank fitted and does coolant flow in and out of the tank?
As far as replacing the spring, I think that is a good idea for no other reason than a hose that continually collapses will eventually delaminate and fail when under pressure.