What Is a Radiator Drain Petcock?

A car engine

A radiator drain petcock is one of the more modern additions to vehicles to make maintenance of the cooling system easier. In older cars, a radiator had to be completely taken out for draining because of the absence of a radiator drain petcock. With new cars equipped with the tiny device, draining a radiator has become easier than ever.


One of the most common questions among car maintenance circles involves finding the radiator drain petcock. It is not as difficult to find though. You can locate it underneath the radiator of your car if you lift the front of your car with a jack. The petcock is a small bolt right under the radiator and easy to spot as modern radiators do not have any other holes underneath them that would require bolts. Usually, the underside of a car radiator is covered by a plastic panel which can be easily removed to reveal the radiator drain petcock. Unscrewing the petcock then is a really easy job and requires simple mechanic tools.


The major function of the radiator drain petcock is not only to stop coolant from leaking through the hole underneath the radiator, but it serves a reverse role too. The petcock has been placed in modern cars to make draining a radiator an easy task. Like mentioned earlier, the same task was a pain to perform in older cars as taking out the radiator completely was a complicated process and usually required more than one mechanic to avoid tipping the radiator which could fall and get damaged. The radiator drain petcock ensures that by just unscrewing it, all the fluid from the radiator can be collected easily by keeping a bucket underneath the car without having to move the radiator an inch.