What should you do if all the brake fluid has leaked out?

When all the brake fluid has leaked out, the correct response is to find the leak, repair it, and then fill and bleed the brake system. This is crucial because the braking system relies on hydraulic fluid to function properly; without sufficient brake fluid, the brakes cannot engage effectively, posing a serious safety risk.

Simply filling the brake fluid reservoir without addressing the leak would not solve the underlying problem. If there is a leak, the new fluid would quickly escape again, leading to the same dangerous situation where brakes may fail. Moreover, bleeding the brake system after refilling is essential to remove air bubbles that may have entered the lines during the fluid loss, ensuring that the brakes operate properly.

Checking tire pressure or attempting to drive to a mechanic without stopping would not address the urgent issue of brake failure and would significantly increase the risk of a crash. Therefore, taking immediate action to locate and fix the leak, followed by restoring the brake fluid and ensuring the system is bled properly, is the safe and correct approach.