How to Check How Much Brake Fluid is Left?
4 Answers
When a vehicle has been driven normally for 40,000 kilometers or the brake fluid has been used continuously for more than 2 years, it needs to be replaced in a timely manner. Below are some references for brake fluid replacement: 1. During driving, if the brake warning light comes on or flashes during emergency braking or continuous braking, it may be due to a lack of brake fluid, requiring timely inspection and replacement. 2. During emergency braking, if the braking distance is significantly longer than before, and factors related to the brake pads are ruled out, it may be caused by the brake fluid. It is recommended that the owner address this issue promptly to avoid problems during braking. 3. When pressing the brake pedal, if you feel a soft or weak response, it may be due to deteriorated brake fluid. This is especially noticeable during continuous or frequent braking, where the pedal feels much softer and more elastic than before, requiring immediate attention. 4. If you experience inconsistent braking pressure (sometimes light, sometimes heavy), it is also caused by deteriorated brake fluid. Excessive moisture in the brake fluid can lead to high temperatures during braking, turning the water into steam, which may result in unstable braking performance.
Open the front hood and locate the white translucent plastic container marked with the brake symbol in the engine bay. Checking it yourself is quite simple—there are MIN and MAX level marks on the container wall. The normal fluid level should be between these two lines, slightly toward the upper side. If the level drops below the MIN line, braking distance will increase or even fail, requiring immediate repair. A quick reminder: brake fluid absorbs moisture easily and degrades, so for regular household cars, it's recommended to test its moisture content every two years. Otherwise, rust in the brake lines can cause serious issues. I've seen many car owners neglect fluid changes, leading to corroded brake master cylinders and leaks—repair costs can be ten times the price of new fluid.
Just helped my neighbor with this issue last week. The procedure is actually three simple steps: With the engine cold, pop the hood and locate the round or square brake fluid reservoir. The translucent reservoir has raised/lowered level markers on the side. Key point – the normal fluid level should at least cover the MIN mark. If you notice the fluid has turned dark like coffee grounds or there are metal particles settled at the bottom, it means a complete flush is needed. Don't rush to top up if you see the level drop – first check your brake pad thickness, as fluid depletion can be normal wear indication. Important reminder: Mixing different DOT grades will cause flocculation, and fixing that could easily cost thousands.
A common inspection method used in auto repair shops is to first clean the outer wall of the reservoir and check if the fluid level is within the marked range when the engine is cold. Special attention should be paid to vehicles with ESP, as they require connecting a diagnostic tool for bleeding the system. Adding fluid randomly may damage the hydraulic unit. There are typically three reasons for actual fluid level drop: brake pad wear exceeding 7mm, wheel cylinder leakage, or master cylinder seal aging. The most troublesome case I've seen was a certain German car model where the fluid reservoir was hidden beneath the battery, requiring removal of a protective panel to inspect. Keeping some brake fluid in the car for emergencies is acceptable, but if the level falls below the minimum mark, professional inspection and repair are mandatory.
