Symptoms
- Brake fluid reservoir below the minimum line
- Possible brake warning light on the dash
- Pedal may feel normal or slightly softer than usual
Likely causes
- CommonNormal fluid drop from worn brake padsAs pads wear thinner, brake fluid shifts into the calipers, lowering the reservoir level.
- PossibleSlow leak in a line, hose, or caliperA leak too small to see as a puddle can still steadily lower the level.
- Less commonFluid not topped off after a recent brake jobWorth checking if this happened recently after service.
What to do
- Check pad thickness through the wheel spokes if visible, or check maintenance records for the last pad replacement.
- Look under the car and near each wheel for any signs of wetness, even small amounts.
- Top off the reservoir with the correct DOT-rated brake fluid up to the max line, without overfilling.
- Recheck the level after a week or two to see if it's dropping again without new pad wear to explain it.
- Have pads replaced if they're worn thin, which is the most common and simple explanation.
- Have a mechanic pressure-test the system for leaks if fluid keeps dropping with healthy pads.
Tools and parts
Brake fluid, DOT rating from owner's manualSearch: “DOT 3 or DOT 4 brake fluid for your car”
Brake padsSearch: “brake pads for your car make and model”
When to call a pro
See a mechanic if fluid keeps dropping without corresponding pad wear, since that points to a leak that needs to be found and repaired.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.