Brake fluid leak

Symptoms

• Clear to light amber, slightly oily puddle near a wheel or under the master cylinder area (near the firewall on the driver's side)
• Brake pedal feels soft, spongy, or sinks toward the floor
• Brake warning light illuminated on the dashboard
• Brake fluid reservoir level reads low

Likely causes

• CommonLeaking brake line or hoseRubber brake hoses or metal lines can corrode, crack, or get damaged by road debris, leaking fluid near a wheel.
• CommonLeaking wheel cylinder (drum brakes) or caliper (disc brakes)Internal seals in these components wear out and let fluid leak, usually visible as wetness right at the wheel.
• PossibleLeaking master cylinderLocated under the hood near the firewall on the driver's side; a leak here can drip inside the car or under the hood.

What to do

1. Stop driving the car if the brake pedal feels soft, sinks to the floor, or the brake warning light is on; this is a safety-critical issue.
2. Check the brake fluid reservoir level; if it's noticeably low, treat this as confirmation of a real leak rather than just topping it off and continuing to drive.
3. Look for wetness at each wheel (calipers, wheel cylinders) and along visible brake lines for the leak's location.
4. Check under the master cylinder near the firewall (driver's side, under the hood) for leakage there.
5. Do not attempt to just top off brake fluid and keep driving normally if the pedal feels off, since air or continued fluid loss in the brake system is dangerous.
6. Have the vehicle towed or driven minimally and carefully to a shop for immediate repair if a leak is confirmed.

Tools and parts

When to call a pro

See a mechanic immediately for any suspected brake fluid leak; this is a safety system that should not be diagnosed-and-delayed like other fluid leaks.

Safety