What are the reasons for low brake fluid level?

2 Answers
OBrantley
07/24/25 12:08pm
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.
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DeLucas
08/11/25 6:18am
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.
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