I agree on the problems with the fail safe design.The 216 on my truck must be burped when I refill it with coolant. It will never recover by itself. I open the heater hose connection at the thermostat housing and close it after all the air has escaped during filling. The 216 in my 38 does not present this problem.
Leaving the rad cap off on an unpressurized system will not change anything.
