Hydraulic brake systems rely on hydraulic fluid pressure to activate the vehicle's braking mechanism. When force is applied to the brake pedal, the piston in the master cylinder generates hydraulic pressure. This pressure is transmitted through the brake lines to the wheel cylinders, where it engages the caliper piston. The caliper piston then presses the brake pads against the brake disc. This action creates friction, which slows down the wheel's movement, ultimately bringing the vehicle to a stop.

DOT 3 and DOT 4 glycol-ether based fluids are commonly used in hydraulic brake systems. These brake fluids are hygroscopic, meaning they absorb moisture from the environment even under normal atmospheric conditions. The presence of water in the brake fluid lowers its boiling point, which can adversely affect braking performance. Therefore, it is recommended to replace the brake fluid every 1 to 2 years to ensure optimal performance.

Features of Hydraulic Brake Fluids:

• High Boiling Point: Ensures that the fluid can withstand high temperatures without vaporizing, which helps maintain effective braking performance.
• Low Freezing Point: Prevents the fluid from freezing in cold conditions, ensuring reliable operation in various temperatures.
• Corrosion Protection: Guards metal components within the braking system against rust and corrosion.
• Compatibility: Works well with plastic and rubber materials used in the brake system.

Main Standards and Specifications for Hydraulic Brake Fluids:

• FMVSS 116 (Federal Motor Vehicle Safety Standard): A standard set by the U.S. government for brake fluids used in motor vehicles.
• SAE J 1703 (Motor Vehicle Brake Fluid Standard): A standard by the Society of Automotive Engineers that specifies performance requirements for brake fluids.
• DOT (Department of Transportation): The regulatory body that sets the standards for brake fluid performance and safety.

Maintaining the recommended brake fluid specifications and regular changes are essential for ensuring the reliability and safety of a vehicle's braking system.