Cooling system cavitation is nothing more than tiny vapor bubbles that form in liquid coolant. They form at local hot spots in the cooling system and/or in local areas of low pressure, like the inlet side of the water pump. When bubbles enter a high-pressure area, they collapse and act like tiny explosions. If they collapse in contact with metal, pitting and erosion will occur. Cavitation damage can be rapid and extensive, and its prevalence is affected by cooling system and water pump design, engine operating conditions, the condition of the cooling system and of the coolant itself.