She may be dead, Jim!

[cornontherob]

Change the cap again? Run the car and let it warm up. If what I'm getting from this is correct, you're saying you drove it on the new radiator cap, and then opened up the trunk and there was coolant everywhere?

Could have been the cap failing. I can't remember if there's a gasket or o ring on the cap. But check that. Change it and see if it leaks more. Look for condensation in your oil fill tube and a milkshake in your oil or coolant. Both are the signs of intermix and/or a cracked head. IMO I think it's just the cap. Start small and work your way up. Don't replace your heads because a plastic cap got you.