Low amounts of coolant and/or debris in the radiator can lead to a loss in the ability of the cooling system to do its job. This could result in the engine overheating.
Thermal shock, the uneven expansion of materials, is created when the coolant temperature fluctuates rapidly and repeatedly.
If thermal shock occurs, it almost always compromises the integrity of the gaskets in the affected area. In turn, this means these gaskets are likely to fail prematurely and will continue to fail unless the cause of thermal shock is eliminated.