Seal internal external and coolant-to-oil leaks with Bar s Leaks Radiator Stop Leak. It is specially formulated to seal larger leaks better than other stop-leak products. The radiator heavy duty stop leak works safely and effectively on plastic aluminum and metal radiators. It also works with heater cores blocks heads gaskets and freeze plugs. The formula includes special water pump lube lubricants that seal and inhibit the formation of rust and scale. It bonds quickly to resolve your problems and get you on your way. Good for rapid repairs this formula makes a nice accessory for the garage or as part of your emergency vehicle kit. Seal pipes and prevent further engine damage with the Bar s Leaks Radiator Stop Leak.