Hi there, noob here don't know if anyone had this problem couldn't find anything on the search engine but I just got my first Grand Prix GT 2001 3800, noticed it was over heating so I let it cool down and checked the coolant and found some white/black/brownish guu under the cap? Never seen this before. Couple days after the the white part starting turning into a brownish color. I poured in some Prestone antifreeze and filled it up but after running around for few hours, and letting it cool down checked it again, it needed more so guessing there's a leak somewhere too? And the "coolant low" light always stays on? The car has about 175,000 miles on it. Could really use some help here. Thanks.