just a thought
Have you ever had it off of the car to look inside it?
when I took my car apart last year for the motor rebuild, my lower radiator hose was hard as a rock, come to find out there was a spring inside of it, I guess to keep it from collapsing maybe. I have never heard of this being the case on upper hoses, but just something for thought.
I would say, if you have the appropriate cap on the radiator you should be okay.
Have you changed a t stat or anything lately, maybe theres some air in the system. If you think it would help you could try burping the system.