Mazda 3 Coolant Overflow Tanks

A coolant overflow or recovery tank is a crucial part of the engine cooling system, which is needed to retain some quantity of coolant when it gets hot and expands. There are two main types of this reservoir, pressurized and non-pressurized, and their working principles are somewhat different. The latter is simpler; usually, it's a white molded plastic tank with a threaded plastic cap, an always open vent channel, and a tube connected to the radiator's filler neck. When the pressure in the radiator reaches a certain limit, the spring valve in its cap allows some quantity of hot liquid to get into the reservoir.

When engine temperature reduces, the coolant returns via the same tube into the radiator because of vacuum. In pressurized reservoirs, the radiator may not even have a cap – it's located on the tank that has two sections inside. Like the rest of the system, it's always under pressure, and the cap usually contains a written warning about that. The pressure in the upper section of the reservoir is used to push the coolant back into the system. Such a system can be found in the Mazda 3 and many other vehicles. Here you can select from an assortment of Mazda 3 coolant overflow tanks.