Had my 99 park avenue 3800 II plenum and lower intake gaskets fix, cool with in two weeks my car had consumed a full resivor of coolant, no exterior leaks could be seen. but kept adding coolant. Did my research, and found all the talk bout the 3800 and 3.4 & 3.1 liter engine with dex cool and gaskets.. BUICK dealter told me $625 to replace both if needed, my mechanic she only charged me $358.. She showed me that there was a hole in the plenum also showed me in due time the gasket was bound to fail, with all the weak spots in it. She replaced it with a thicker gasket...
Thanks Sandy you are a awesome mechanic