Check condition of brake fluid in less than a minute! Water can enter a brake system through microscopic holes anywhere in the system. Once inside, it can cause corrosion in system components it can vaporize under the high heat conditions of hard braking situations it can cause dangerous degradation of your customer's ability to stop safely! The No. OTC-3890 lets you find out if your customers are safe or not in under a minute. It actually boils a small sample of brake fluid in the reservoir to test for water contamination.