How to Know When to Replace Brake Fluid?

[McBarrett]

Brake fluid does not have a specific replacement interval. The replacement criterion is based on testing its water content. When the water content in the brake fluid exceeds 3%, it must be replaced. Here are some details about brake fluid: 1. Brake fluid is an oil: But it is not a lubricating oil. It is not used to lubricate the brakes but to transmit hydraulic pressure. Based on the usage characteristics of brake fluid, the main criterion for determining whether it needs replacement is its water content. Since brake fluid is hygroscopic, some water molecules from the air can gradually permeate into the brake fluid through various pores, causing the water content to increase. When the water content reaches a certain level and the brakes are frequently applied, the compression of the brake fluid can cause the water inside to expand due to excessive temperature, potentially leading to reduced braking performance, such as ineffective or continuous braking. 2. The most direct way to determine the water content in brake fluid: Use a test pen for measurement.

[OReagan]

As an ordinary person who drives frequently, I've noticed several obvious signs indicating when brake fluid needs replacement. When you press the brake pedal and it feels spongy or has longer travel distance with reduced braking power compared to before, this likely means the fluid quality has deteriorated. Brake fluid gradually absorbs moisture from the air, causing it to become cloudy over time and change color from light yellow to dark brown or black - you can check this by looking at the reservoir under the hood. If you notice a burnt smell or the fluid level is too low, these are also warning signs. I recommend checking every two years or considering replacement after about 20,000 kilometers. Excessive moisture in the fluid lowers its boiling point, which can lead to brake failure during aggressive driving and even corrode metal components in the braking system, potentially causing leaks or more serious malfunctions. Don't ignore these small signals - safety comes first. Replacing the fluid early can prevent costly major repairs later.

[OFinn]

From a maintenance perspective, I believe regularly testing brake fluid moisture content is a reliable approach. When brake fluid absorbs moisture, its performance degrades. You can use specialized test pens or strips to check moisture levels - replacement is recommended if exceeding 3%. Alternatively, have technicians at professional repair shops measure it with instruments for greater accuracy. Abnormal braking symptoms like pedal vibration or delayed response also serve as indicators. Generally, brake fluid should be replaced every two years or 25,000 kilometers, though this depends on your driving habits and environment. Frequent driving in humid areas accelerates moisture absorption. Neglecting fluid changes may lead to vapor lock, resulting in longer braking distances or even failure, creating safety hazards. I always record the last replacement date in my vehicle and follow the manual's recommended maintenance schedule for peace of mind.

[IkerAnn]

From a safety perspective, the signs of brake fluid replacement are directly related to system performance. If the brake pedal feels spongy or makes unusual noises when pressed, it's time to consider checking the fluid quality. Aged fluid has a lower boiling point and is prone to forming bubbles under high temperatures, affecting braking efficiency. Be alert when the color changes from clear to dark or cloudy. Check the fluid reservoir level and condition approximately every 20,000 kilometers to maintain optimal performance and prevent corrosion of wear components. Never wait until brake failure occurs to take action—the risks are too great.