Vehicle tank for brake system liquid

The tank (100) has a purging apparatus (200) with a head (210) supported on an elongated neck (110) in a sealed manner, and a plastic level gauge realized independently of the tank and including a top end and a bottom end that are opened. Positioning elements define a setpoint filling level (NR) when the gauge is installed in the neck and are constituted by a centering tab, a centering and stopping ring and a shoulder. The bottom end opens at a height of the setpoint level. The top end is located above a reference level (No) for sealingly receiving an end fitting (211) of the head.