What are the reasons for low brake fluid level?
3 Answers
Car brake fluid level is low for the following reasons: 1. The brake caliper piston leaks oil, causing the brake fluid level to be low. At this time, it is necessary to check whether the brake oil pipe is aged or broken, and whether the caliper piston is leaking oil. If so, the brake fluid level will be low. 2. The vehicle's brake pads are severely worn or have reached the wear limit. The severe wear of the brake pads during operation creates gaps, and the gaps are compensated by the brake fluid to make up for the expansion and contraction distance of the brake caliper, resulting in a low brake fluid level. 3. Normal consumption of brake fluid and insufficient oil volume cause the brake fluid level to be low. During the vehicle braking process, the movement and wear of internal components lead to brake fluid consumption, which may result in insufficient oil volume and a low brake fluid level.
After running this auto repair shop for so many years, I've seen low brake fluid levels countless times. The common causes include brake system leaks, like loose pipe fittings or aging seals that allow fluid to slowly seep out. Worn brake pads are another factor - as the pistons extend further, they occupy more fluid space. Improper maintenance also plays a role, such as not filling to the full line during fluid top-ups or minor evaporation from prolonged high-temperature driving. Less commonly, air intrusion into the master cylinder could be the culprit. I'd advise car owners to first check brake pad thickness - replace them if they're beyond the wear indicator. Then inspect for oil stains on the ground and undercarriage to ensure no pipe leaks. The braking system must always function properly; low fluid levels increase pedal travel and delay response, making high-speed emergency stops particularly dangerous. Making it a habit to check the reservoir dipstick monthly, keeping fluid between MIN and MAX lines, is smart preventive maintenance.
I remember the first time I noticed the brake fluid level was low was after a long trip, and I was a bit panicked. After talking to the mechanic, I learned it was mainly due to severe brake pad wear, which caused the piston position to change and the fluid level to drop—a natural phenomenon but something to keep an eye on. Another reason could be leakage, such as damaged seals or loose pipe connections, where fluid slowly seeps out. Some cars may experience slight fluid evaporation when parked for long periods or in high-temperature environments. Back then, I checked the brake pads myself and found they were indeed thin. When replacing the pads, I topped up the fluid and adjusted it accordingly. This issue shouldn’t be taken lightly, as low fluid levels can make the brakes feel soft or less responsive, especially in rainy conditions or when going downhill, increasing the risk. Now, I’ve made it a habit to check the fluid level and brake condition every quarter to ensure safety. If any issues are found, I address them promptly to avoid secondary damage to the calipers or ABS system.
