You saw what you saw, but I'd sure like to know the science behind it. It's a puzzler for sure. Pressure in a closed cooling system is equal everywhere. The pressure in the system is the result of expansion, nothing to do with the pump. Those centrifugal pumps don't make enough suction or pressure to move a needle on a gauge, never mind collapse a hose (pull the supply side heater hose and put your finger over the end).
In thinking about it further, I suspect that the engine on a dyno is not connected to a closed system with a rad, but rather to a system with it's own pump. Might have something to do with that.
I always thought the springs were in there to prevent kinking on a bend.
Well, pumps are doing something, after all - namely, circulating coolant.
They have a suction and a discharge side as a result - all pumps do.
(Part of my trade for the last 35+ years - fire pumps)
Suction is read in psi, as is discharge pressure - because the pump does indeed generate pressure, both positive and negative.
Yes, the bottom hoses on our big blocks are the suction side of the pump.
Another aspect of this subject that hasn't really been discussed is the quality of the hoses being made today. I submit, again my opinion, that they aren't as stout as they used to be and that they may not even be made of the same chemical composition as say 30 years ago.
When I contacted a couple of the manufacturers' engineering departments about this subject (why they don't use springs anymore), the consensus was that they claimed todays' hoses are made of better quality materials and that the old school hoses' biggest failing point usually was a separation of the inner lining from the outer, hence the need for a spring.
Their claim is that this cannot happen with modern constructed hoses because of how they're made and what they're made of.
I dunno, sure is easy for me to take a new one and collapse it in my hand....
Yes, a moderate to sharp bend in a hose is a natural place for a kink/collapse to occur, so springs helped with that no doubt.
Final point from me on this subject:
If springs aren't needed in hoses anymore, then why are most of those universal type hoses constructed with a heavy outer spiral (many with actual steel springs impregnated in the poly/rubber itself)?
So they won't collapse as you contort them into the desired position, that's why.