[Jim A]

I finally stopped worrying about my cooling system 50 years or so ago.
The pressure cap may already have lost its spring seal when I got my '60 1500.
At every check the coolant level would be down a couple of inches. If I topped it off, it would be back down next time I checked.
If I didn't top it off, it would maintain the low level, never going lower.
Ever. Long trips or short, winter or summer.
All that, of course, with no pressure.
Putting a new cap on now would probably blow something.