300m - Leaks - Radiators :: 2000 - Coolant Boiling In Reservoir Tank

2000 Chrysler 300M with 142K miles. Was a very reliable car until recently.

Problem began with boiling coolant in the reservoir tank. Then began to lose coolant at a high rate. I tried stop leak products and replaced the coolant frequently for a couple months. Some of it kind of worked, but the problem always returned. The car drives fine for about 10 highway miles then begins to steam out from under the hood on the passenger side. It gets about half way up the temp gauge, but does not really overheat. I usually stop when it steams out, let it cool, replace the antifreeze, then do it all over again. I've also tried a bunch of other things too, e.g., radiator flush. None of it worked.

The mechanic wants to replace the radiator. Says the system does not have pressure so there's no real way to determine if there are leaks in the engine. But he does know that the radiator is no good. I'm okay to replace radiator, but don't want to do it just to find out ten minutes later that I have a blown head gasket, which I would opt not to fix. I have read the tell tale signs of a blown head gasket, such as coolant in the oil, but there is none. My exhaust is white, but it's 5 degrees outside and it doesn't look whiter. I have seen some coolant on the ground at times.