Liquid glass can be added to a coolant system on a vehicle to seal leaks caused by a blown head gasket. It is a sodium silicate that crystallizes in cracks when it dries, providing a temporary barrier and is most effective when used on cars with iron cylinder heads.
Vehicles with aluminum engine blocks, or heads, require a more specialized product. The expansion properties of aluminum cause liquid glass to fracture, and fail, quicker than it does on engine heads constructed from iron.
Repairs with liquid glass require owners to park the vehicle on a level surface, with the engine cool. The front end of the automobile needs to be jacked up, in a safe manner, so the petcock valve can be accessed to drain about 1 gallon of coolant. The entire contents of the liquid glass container need to be poured directly into the radiator or coolant system. This should be done through the radiator cap, or hose, and not through the reservoir normally used to add engine coolant.
The engine needs be started and idled for at least 20 minutes to allow the fluid to circulate. Then it should be shut down and allowed to completely cool. Flushing and replacing the coolant is necessary to remove the remaining liquid glass and prevent it from damaging the water pump or clogging the coolant passages. It is a good idea to change the oil and filter, because it is usually contaminated with water from the head gasket leak.