“Brake fluid doesn’t dissipate,” Chang explains. “Brake fluid is low because it went into the pistons because your brake pads ...

The brake fluid reservoir is usually plastic and clear or semi-translucent. This allows you to visualize the brake fluid ...

but like brake calipers, sometimes it can spring leaks or otherwise fail, and it must be rebuilt or replaced. The master cylinder is topped by the brake-fluid reservoir, which must be kept full.