K-Seal (ST5516-12PK) HD Permanent Coolant Leak Repair - 16 oz., (Pack of 12) Fixes most leaks in all types of water cooled engine including cracked heads, head gasket failures, cracked blocks, radiators, heater cores and water pumps Mixes with all types of antifreeze and coolant; no need to drain or flush the system before or after treatment A repair made with K-Seal HD is permanent, guaranteed for the lifetime of the engine Easy to use; shake the bottle; add it to the cooling system and go 16 ounce