What are the main components of brake fluid?
2 Answers
Brake fluid is composed of the following components: 1. Component one: Polyglycol ether solvent, approximately two-thirds. Polyglycol has very high viscosity, so polyglycol ether is used to dilute it. Polyglycol ether ensures that the solvent functions properly in the fluid. 2. Component two: Lubricant base fluid, approximately one-third. The base fluid generally refers to polyglycol, used as a lubricant, accounting for about one-third of the brake fluid. These base fluids are obtained through complex chemical reactions of alkylene oxides (ethylene and propylene) with glycol or water. 3. Component three: A small amount of additives. Brake fluid requires the addition of a few additives, such as corrosion inhibitors and antioxidants, which effectively protect the brake system from corrosion, slow down the oxidative decomposition of substances, and limit the formation of acidic decomposition products and resins. Although these additives are added in small quantities, they are crucial and can significantly extend the lifespan.
In the main components of brake fluid, the most commonly used are glycol ether compounds, which are prevalent in DOT 3 and DOT 4 types. I know it typically contains glycol, additives such as antioxidants and corrosion inhibitors, which function to prevent system rust and maintain smooth hydraulic system operation. The boiling point is crucial, as the formulation is designed with a high boiling point to avoid vapor lock during aggressive braking, which can lead to brake failure—a highly dangerous situation. Brake fluid is also hygroscopic, and over time, absorbed moisture lowers the boiling point, necessitating regular replacement—generally every two years or around 40,000 kilometers. I’ve seen different vehicle models use different fluid types; DOT 5 is silicone-based, non-hygroscopic but more expensive and less compatible, so it’s essential to consult the vehicle manual when selecting fluid.
