Symptoms
- Puddle or wet spot under the car, often clear to slightly yellow or brown fluid
- Brake fluid reservoir level dropping over time
- Possible soft or sinking brake pedal
Likely causes
- CommonWorn or cracked brake line or hoseRubber hoses and metal lines both degrade over time, especially in areas with road salt.
- CommonLeaking caliper sealInternal seals wear out and let fluid seep past the piston.
- PossibleLeaking wheel cylinder (rear drum brakes)Similar to a caliper leak but on drum brake systems.
- PossibleLeaking master cylinderUsually shows fluid near the firewall or under the brake fluid reservoir.
- Less commonLoose or damaged brake line fittingCan happen after brake service if a fitting wasn't tightened properly.
What to do
- Check the brake fluid reservoir level and note how full or low it is.
- Look under the car at each wheel and along visible brake lines for wetness or drips.
- Press the brake pedal and note if it feels soft or sinks toward the floor.
- Avoid driving if the pedal feels soft or the leak looks significant; have the car towed instead.
- If the leak is minor and the pedal feels normal, drive minimally and directly to a repair shop.
- Have a mechanic identify the exact source of the leak and repair the line, hose, caliper, or cylinder.
- Have the entire brake system bled after the repair to remove any air that entered.
Tools and parts
Brake fluid, DOT rating from owner's manualSearch: “DOT 3 or DOT 4 brake fluid for your car”
Brake caliper or wheel cylinderSearch: “brake caliper or wheel cylinder for your car make and model”
When to call a pro
See a mechanic promptly to find and fix the source of any brake fluid leak, since it can worsen quickly and affect braking.
Safety
Use caution
If the pedal feels soft or is sinking along with a visible leak, don't drive the car; have it towed and repaired before use.