I own several GM/Cadillacs. As they age, they tend to overheat. An intermittent coolant leak is expected. After replacing radiators, hoses, etc. there were still leaks. I poured a bottle of Bar's Leak 1109 Block Seal Liquid Copper into a 2002 Deville and a 2005 Deville. Both run cooler [since there are no coolant leaks] and the coolant spill tanks remain at their "full” levels. I have been using bar products for over 40 years. They are the best --- the highest quality and efficiency. I would highly recommend this Liquid Copper Stop Leak Cooling System Cleaner.