Bar’s Leaks Heavy Duty Radiator Stop Leak is designed to solve most common cooling system problems, sealing internal, external and coolant-to-oil leaks in radiators, freeze plugs, gaskets, heads, blocks and heater cores. The solution features patented Rhizex pellets that dissolve in minutes to seal leaks. It also conditions the cooling system, lubricates water pump seals and controls electrolysis. Heavy Duty Radiator Stop Leak is compatible with all brands of antifreeze.