Today when I got in my 98 xj limited after itd been sitting in 100 degree weather all day it leAked out almost all it's coolant and had a spray spot on the underside of the hood in front of engine on drivers side (closer to headlight than cab). I put more coolant in it and let it warm up a little longer and drove it 20 miles home and it didn't leak a drop. Any ideas as to what is going on?

 

possible bad radiator cap