One of the most important fluids in your car is brake fluid. Brake fluid is an essential part of the braking system, transmitting force from the master cylinder to all of the car’s brake mechanisms. For the brake system to function safely, the fluid must not lose its properties during operation, such as viscosity at sub-zero temperatures, boiling point, the ability to lubricate components and protect against corrosion of components in contact with it.
The main reason for the loss of its properties is that it can absorb moisture. This can lead to the brake fluid boiling during extreme braking. When the brake system heats up, the fluid boils, forming a vapour lock, which is equivalent to air entering the system, leading to brake pedal failure and loss of control of the vehicle when braking. During winter operation, at sub-zero temperatures, fluid with a high moisture content becomes viscous, which significantly slows down and hinders the braking process. The increased water content in the fluid also has a negative effect on the components of the braking system, with the brake cylinders of your car’s calipers being the first to suffer.
Land Rover recommends replacing the brake fluid every 2 years. However, the quality of the fluid must be checked during each service. The amount of moisture that accumulates in the fluid depends on climatic conditions and operating conditions. Moisture enters the fluid along with air when the pedal is pressed through the compensation hole in the brake system expansion tank.
Typically, the fluid absorbs an average of 1% or more moisture per year. A two-year-old car has an average of 2% or 3%, depending on operating conditions. A 2% water content in the fluid reduces the boiling point by 45 degrees. The percentage of moisture in the brake system fluid can be determined using a special tester.
The LED signals on this tester can be used to assess the condition and boiling point of the fluid. During operation, brake fluid changes its basic properties, so it is extremely important for the safe operation of the vehicle to monitor its condition and replace it in a timely manner.