Blue Devil Coolant Stop Leak (16 oz)

A small coolant leak can turn into an overheating engine surprisingly fast, especially if you are topping off the reservoir every few days and hoping for the best. Blue Devil Coolant Stop Leak is a pour-in formula that circulates through your cooling system and seals minor leaks in radiators, heater cores, freeze plugs, and water jackets while you drive.

What sets this product apart from some competitors is that it contains no solids or fibers. That matters because particulate-based stop leak products can clog heater cores and small passages over time, creating new problems while trying to fix old ones. Blue Devil's formula bonds chemically to metal, aluminum, cast, alloy, and plastic surfaces at the leak point. It mixes safely with all types of antifreeze and coolant, so there is no need to flush the system before adding it.

Pour the bottle into the radiator or coolant reservoir, run the engine to operating temperature, and let the product work through the system. It is most effective on minor to moderate leaks — if you have a major failure like a cracked block or blown head gasket, you will likely need a mechanical repair rather than a chemical solution.