Chrysler Repair Questions? Ask a Mechanic for Answers ASAP
From what you have described, it sounds to me like the pressurised coolant cap has failed and needs replacement.
This is simply the cap on the reservoir, if you remove it and look at the underside you may be able to see the internals.
The device function is essentially to maintain pressure to stop the coolant boiling, similar to a pressure cooker, to release excess pressure, and to allow air back in during the 'cool down' to release the vacuum.
Please try a replacement cap, as long as the information you have provided me is correct, I would think this will resolve your problem.