Brake fluid is the fluid found in the brake system. Its function is to transfer the force from the brake pedal to one (or more) slave cylinders via the master brake cylinder. This then causes the vehicle to brake. In addition to the brake fluids function to brake, the liquid also ensures to preserve a high boiling point and it has a lubricating function. This also means that it’s very important to control the brake fluid level from time to time, because a leak in the system can be very dangerous.