Radiator Drain Plug
A threaded plug or petcock valve at the bottom of the radiator used to drain coolant during service.
A radiator drain plug, often called a petcock, is a small plastic or brass threaded screw located at the lowest point of one of the radiator tanks. Its primary purpose is to provide a clean and controlled way to drain the engine coolant during cooling system maintenance, such as a coolant flush or radiator replacement. The drain plug typically has a rubber O-ring or seal to prevent leaks.
Because these plugs are usually made of plastic and are subjected to heat cycles, they can become brittle and crack. They are also easily broken if over-tightened or turned in the wrong direction during service.
A leaking or broken drain plug will cause a persistent coolant leak at the bottom of the radiator, leading to low coolant levels and engine overheating. Replacing a leaking petcock is a simple fix that involves draining the system, unscrewing the old plug, and installing a new one with a fresh seal.