K-Seal ST5516 HD Multi Purpose One Step Permanent Coolant Leak Repair Permanent coolant leak repair - Just shake, pour and go Mixes with all antifreeze No draining or flushing Fixes cracks and leaks in radiator, head gasket, freeze plugs, cylinder heads, heater core, water pump casing and engine blocks If product did not seal head gasket leak, the system might be Over-pressurized, which causes back pressure and doesn't allow the product to reach the problem area, on this page below under Technical Specification is a PDF Guide with instructions to follow to complete the repair successfully