How often should brake fluid be replaced in a sedan?

[LaHadley]

Sedan brake fluid should be replaced every 2 years. The composition of automotive brake fluid is castor oil and low-carbon alcohol. Brake fluid is an important oil in the car's braking system, serving the function of transmitting force. Situations requiring brake fluid replacement include: 1. When the brake fluid absorbs moisture or contains impurities; 2. When the vehicle experiences inconsistent braking force during normal driving, the brake fluid should be promptly replaced; 3. When the wheel cylinder rubber cup expands excessively; 4. Brake fluid should be replaced every two years. Characteristics of brake fluid include: 1. Good viscosity-temperature performance and low freezing point, ensuring good fluidity at low temperatures; 2. High boiling point, preventing vapor lock at high temperatures; 3. Minimal quality changes, avoiding corrosion and deterioration of metal and rubber.

[LaNaomi]

We long-haul drivers pay special attention to brake fluid condition. During my last maintenance, the technician said regular family cars should change it every two years or 40,000 km, but my old Corolla needs replacement every 18 months due to frequent mountain slope driving. Soft brakes during rainy days are a warning sign! Now I've learned - I always use a moisture tester during servicing and replace immediately if water content exceeds 3%. Brake fluid absorbs moisture easily, and high moisture lowers boiling point, potentially causing vapor lock during continuous braking - that mushy pedal feeling is extremely dangerous. Performance car modifiers should note: upgrading calipers without changing fluid is pointless. Oh, and humid southern regions require more frequent changes than the north.

[DeStephanie]

An auto repair shop tested brake fluid data from hundreds of vehicles. They found that cars with unchanged brake fluid for three years generally had water content exceeding 4.5%, with an extreme case of seven years without replacement reaching 8%. In this state, the boiling point drops from 260°C for new fluid to around 150°C, meaning bubbles can form at temperatures equivalent to frying a steak. Although maintenance manuals often recommend a three-year cycle, it's advisable to test the fluid every two years. A ¥20 test pen from Taobao is quite accurate. Replace the fluid immediately if the pen shows a yellow light; a red light indicates that even rubber hoses may be corroded. Last time, a car with a rusted-through brake master cylinder was encountered, and the repair cost was enough to change the brake fluid thirty times.

[VonAnthony]

When getting maintenance at a 4S shop, they often recommend changing the brake fluid. In reality, you don't need to strictly follow their advice—the key is to consider your driving environment. For my city commuter car used to pick up and drop off kids, changing it every four years is fine, as long as I confirm the water content with a tester. But if you enjoy road trips on mountain roads or frequently carry heavy loads, it's better to change it every two years. Last time, my friend's Golf suddenly had soft brakes on the highway, and after towing it back to the shop, they found the brake fluid had excessive water content. Now, I've taught him to check the color of the fluid reservoir—if it turns cloudy or black, change it immediately; if it's still pale yellow and transparent, it can last a while longer. Remember to fully bleed the air, as residual old fluid can contaminate the new one.

[LePatrick]

Hands-on owners can check like this: First, look at the oil reservoir scale - if it's below the MIN line, you must top up with the same type of oil. Then dip a cotton swab in the oil and drip it on a tissue paper; if you see layered oil-water separation, it's time for a change. Pay attention to pedal feel during daily driving, especially when braking distance noticeably increases in rainy conditions. My second-hand Focus taught me this lesson - the previous owner hadn't changed the brake fluid for five years, and I almost rear-ended someone while parking underground. Now I've bought my own brake fluid change kit. Bosch DOT4 brake fluid costs about 50 yuan per liter, and two bottles are enough for three changes. Remember to pump the brakes vigorously several times after changing to purge air from the calipers.