A radiator is designed to filter out the heat of circulating engine water and "radiate" it into the outside atmosphere. A radiator must be able to accommodate a huge influx of super hot water traveling at fast speeds continuously as an engine is running. If there are any weak spots in the radiator wall or housing, the radiator can start to leak water and eventually burst.
A radiator that is old or faulty or that has not been properly maintained and is dirty can lead to a radiator that overheats and eventually bursts. A radiator is filled with several small channels, or galleys, in which circulating engine water travels through. If any of these galleys are clogged or not functional, the radiator will retain more heat and start to expand and warp, ultimately bursting.
A radiator that has a significant amount of rust buildup within its galleys and walls can lead to radiator leaks and a radiator that eventually bursts. Rust is highly corrosive, and while rust can severely impact the flow of circulating engine water within a radiator, it can also wear away and weaken the radiator wall itself. This combination of restricted water flow, which increases radiator temperature, along with the corrosive effects of rust on the radiator wall can lead to a burst radiator.
