<<Hmm, if the spring clamp is coming off, I suspect you have too much
pressure in that part of the system.>>

And what would cause that to happen Kim, in this area of the engine?
Nothing that I can think of either.
But, if the whole system was being restricted by some sort partial
blockage it would cause pressure to be built up throughout, hence the
failure.
I would suspect something is plugged slowing the input flow to the
radiator, and causing backed up pressure to the rest of the system.

Let's ask this question of the poster;
"When was the last time the system was chemically and pressure flushed,
how often do you change the coolant, and how many miles on the Van?"

This all would be a good indication of whats going on.

<<I hate the "regular" clamps. They tend to cut into the hoses (I just
got a leak from one of them)>>

You haven't seen or used the silicone hose double wrap aircraft screw
clamps.
The outside tightens up as a conventional screw clamp does, the inside
band of the clamp stays stationary to eliminate pinching or tearing.
A superior clamp than the standard stainless hose clamps your familiar
with, and better clamp than even the spring loaded clamps.