Don`t remember if you ever confirmed there was a spring in the lower hose.
I am wondering about the spacing between the condenser and the rad. that has nothing to do with why it suddenly started but did engine swaps change rads, spacing etc?? The condenser gets hot with the ac on right ?? I am sure you have checked the fins in both for damage, road kill or grasshoppers etc.. I saw the results of someone blowing the rad clean,, ya the air pressure bent all the fins.
If it was a Dodge we would know haha

George