I have a 96 regal and I have recently discovered that a bunch of brown gunk has built up inside the radiator and underneath the cap. I want to go about flushing it even though the engine does not overheat or shown any other signs of a bad cooling system. when researching online I have noticed a lot of controversy over the recommended dexcool and saw that this tends to happen in older gm cars that use dexcool when unwanted air is finding its way into the cooling system it gunks up and blocks up the passageways. After i found this out i inspected more and saw that i have puddles of what looks to be orange dexcool seeping from underneath the plenum. My question is do i need a new radiator or can I just flush the system? I think I caught it pretty early considering I couldn't tell it was bad until I opened the radiator cap. also what should I go about fixing first? and should should I upgrade to the aluminum plenum? I believe they updated the 3800s with the aluminum one after 2002 due to this same issue but I may be wrong.