[PeteA216]

Theres a strong possibility that the plastic is cracked, over time thats what happens to plastic under pressure. Same thing happened to my truck. Fortunately it was covered under a lifetime warrantee and my father back when he owned the truck kept the reciept from back in 1997. The guy at Modine was shocked to see one of these come back. He said people usually get rid of the vehicles before the radiator gets a chance to fail... Anyway, if you want to avoid replacing the radiator for now you can try some Bars Leak radiator stop leak. That will solve it temporaraly, but when I say temporaraly, I mean temporary. It may last a week, it may last a year, but if it is the plastic thats cracking, you probably don't have more than a year before it gets serious.