The engine block can be thought of as the core of any internal combustion engine. Solid and containing some of the most important pieces of the vehicle, including the cylinders and the cylinder head, sometimes cracks or leaks occur in the engine block. If you can identify the crack and catch it before anything warps then chances are good that you can use a do-it-yourself engine block sealant to seal up the crack from the inside.
Let the car's engine run completely cold. Leave it off for at least an hour to allow all of the heat to dissipate for the purpose of introducing the block sealant.
Open the hood and brace it so that you can look at the engine. Remove the radiator cap and examine how much fluid is in the radiator. For radiators that don't have a cap, remove the top hose and look down into the radiator.
Pour recommended amount of engine block sealant into the radiator. The amount will vary based on your car's engine size, so read the instructions on the side of the bottle to see just how much you need to add. Replace the radiator cap once it's been added.
Get behind the wheel. Turn the heater and the fan to maximum, and then turn the car on. Leaving the vehicle in park, run the engine at roughly 1,000 rpms for 60 minutes. Once the 60 minutes are up, immediately shut the engine down and let it cool completely once more.
Top off the radiator with antifreeze and water. Leave the sealant in the vehicle and drive as normally. Once the car has been run through the initial bonding phase, the sealant will have found the crack and bonded to it due to the temperature difference as the sealant was pumped through the engine block.
