REPAIRS IN MINUTES: Permanently fix blown head gaskets, cracked heads and cracked/porous blocks including aluminum heads in old and new cars. The only head gasket and block sealant that is 3rd party tested to meet ASTM D3147. Save time/money | SEALS CRACKS AND STOPS LEAKS: A DIY alternative to costly repairs, our head gasket fix permanently seals cracks and holes! Quickly repair your blocks, leaking radiator, freeze plug, heater core and water pump casing with no adverse impact on efficiency. | POUR AND GO: Our head gasket sealer is easy to use just shake, add to your radiator/overflow and run the engine! Unlike some competitive products, it mixes with all types of antifreeze, absolutely no draining, flushing or pulling the thermostat required. | SCIENTIFICALLY TESTED: Safe, effective, our head gasket and block repair seals leaks up to 1/32 of an inch! Once cured, the repair withstands the high pressure of the combustion chamber, all without failing or clogging the cooling system. US Bestseller | CUSTOMER SUPPORT: If our head gasket repair leak doesn’t seal your intake gasket, the system might be over-pressurized. Check the Technical Specification section of this page for extra instructions for a successful repair. Over 8 million bottles sold.