Does Brake Fluid Need to Be Replaced?
3 Answers
Brake fluid needs to be replaced, and the replacement method is as follows: 1. Place the vehicle on an inspection pit or lift it with a jack; 2. Clean the drain port, remove the dust cap, loosen the drain screw, repeatedly press the brake pedal until the fluid runs clear, then tighten the drain screw; 3. Add new brake fluid. Characteristics of brake fluid: 1. Very low freezing point: maintains good fluidity in low temperatures; 2. High boiling point: prevents vapor lock under high temperatures; 3. Minimal quality changes: does not cause corrosion to metal or rubber. The function of brake fluid is to transmit hydraulic pressure from the master cylinder to the wheel cylinders, where the pistons, under the action of the seals, push out to apply force on the brake discs and pads, thereby enabling the braking function.
I've encountered this issue three times. The first time was when I was driving an old Jetta down a long slope, and the brakes suddenly lost power. The second time was during an emergency stop on a rainy day, and I felt the braking distance was significantly longer. The third time was during a maintenance check when the mechanic said the brake fluid reservoir was cloudy and yellow. Every time, it was the brake fluid causing the trouble. This stuff absorbs moisture from the air, and over time, the water content can skyrocket. The boiling point can drop from 260°C to as low as 150°C. If you're doing an emergency stop on the highway, the brake disc temperature can reach 200°C, and if the fluid boils, it's game over. I recommend checking the maintenance manual—Japanese cars usually need a change at 40,000 km, German cars at 30,000 km, and in humid areas, you should change it even sooner. Don't believe the 'maintenance-free' claims; brake fluid must be replaced.
The first thing I did after getting my used car was to replace the brake fluid. The previous owner hadn't changed it for three years, and the fluid had turned black like soy sauce. The new fluid is light yellow and transparent, while the old one was cloudy with sediment. The mechanic said this fluid is highly corrosive and can damage the ABS pump and brake cylinder seals. He used a device to test the water content, and since it exceeded the limit, we replaced it immediately. The labor cost was 200 yuan, and the fluid was just a few dozen yuan, totaling less than 300. Changing it based solely on mileage is too mechanical; it's better to test it before the rainy season in the south. Last time when I helped a neighbor change the fluid, we found the brake line was corroded and leaking, almost causing brake failure. Catching it early saved a lot of money.
