I have a 2001 Frontier. This morning it got in the 20s. I was warming the truck up and noticed antifreeze dripping from the radiator. Once I got it the basement to find the leak it had stopped. There was antifreeze on the bottom of the radiator but the rest of it was dry. The hoses and cap didn't appear to be leaking. I wiped the antifreeze off and started the truck and the leak appeared to have stopped? I drove it to work and still no leak? Any ideas?