Brake fluid is what transfers the force from your foot on the pedal to the calipers that squeeze your rotors. Without it, pressing the brake pedal does nothing. A leak anywhere in the system means that hydraulic pressure is slowly escaping — and your stopping power is going with it.
The tricky part? Brake fluid leaks are often slow and hidden. You might not notice anything until your pedal feels soft, your stopping distance increases, or a warning light comes on. In Sioux Falls, cold winters accelerate seal deterioration and rust on brake lines, making leaks more common than in milder climates.
Here's how to catch a brake fluid leak early — and what to do when you find one.
5 Warning Signs of a Brake Fluid Leak
Brake Pedal Sinks to the Floor
If your pedal feels soft, spongy, or slowly sinks when you hold pressure at a stop light, hydraulic fluid is escaping. This is the most dangerous sign — your braking force is actively reduced.
Stop DrivingBrake Warning Light On
Your dashboard brake light or ABS light means the system detected a pressure or fluid level drop. Don't ignore it — this is your car telling you the braking system isn't operating normally.
Get Inspected TodayFluid Spots Under the Car
Brake fluid is clear to light yellow (or brown if old), slightly oily, and has a faint chemical smell. Check near the wheels, along the frame rails, and around the master cylinder under the hood. Any wet spots in these areas need attention.
Inspect SoonLow Reservoir Level
Pop the hood and check the brake fluid reservoir — it's a small translucent container near the firewall. If the fluid is below the "MIN" line, fluid is going somewhere. Normal brake fluid loss is essentially zero between service intervals.
Don't Just Top Off — Find the LeakLonger Stopping Distance
If your car takes noticeably more distance to stop — especially at highway speed — reduced hydraulic pressure from a leak could be the cause. This gets worse gradually, so it's easy to miss until it's serious.
Schedule InspectionWhere Brake Fluid Leaks Happen
Not all leaks are visible from outside the car. Here are the 5 most common locations and what to look for at each one.
Master Cylinder
What it does: Converts pedal pressure into hydraulic force for the entire brake system.
Leak sign: Fluid on the firewall behind the engine, or a spongy pedal with no visible external leak (internal failure leaks into the brake booster).
Why it's serious: A master cylinder failure can cause total loss of braking.
Steel Brake Lines
What they do: Carry fluid from the master cylinder to each wheel along the vehicle frame.
Leak sign: Wet spots along the underside of the car, rust bubbles, or visible corrosion on the lines.
SD risk: Road salt and freeze-thaw cycles corrode steel lines from the outside in. Common on vehicles 8+ years old in South Dakota.
Rubber Brake Hoses
What they do: Flexible connections between the steel lines and the calipers at each wheel.
Leak sign: Wet or swollen hose near the wheel, visible cracking, or fluid dripping from the caliper area.
Why they fail: Rubber deteriorates with age, heat, and road debris. Usually the first flexible component to go.
Caliper Piston Seals
What they do: Seal the hydraulic piston inside each brake caliper.
Leak sign: Fluid on the inside of the wheel or dripping from behind the brake rotor.
Cause: Heat cycling and age cause the rubber seal to harden and crack.
Bleeder Valve Screws
What they do: Small screws on each caliper used to bleed air from the system during service.
Leak sign: Crusty deposits or wetness around the valve stem on the caliper body.
Fix: Often just needs proper tightening or a new valve. Prevented by regular brake fluid flushes.
How Urgent Is Your Brake Fluid Leak?
Monitor Closely
Reservoir slightly low but pedal feels normal. No visible spots. Check again in a few days — could be pad wear lowering the level.
Fix Within a Few Days
Small wet spot under the car. Reservoir noticeably low. Pedal feels slightly softer than usual. Schedule a brake inspection.
Stop Driving — Call Now
Pedal sinks to floor. Brake + ABS lights on. Visible fluid dripping. Burning smell from wheels. Call (605) 376-2130
Found a Leak? Here's What to Do
Slow Leak — Pedal Feels OK
Schedule a brake inspection within the next few days. Don't just top off the reservoir — that masks the problem. We inspect all lines, hoses, calipers, and the master cylinder to find the source.
Active Leak — Pedal Is Soft
Don't drive. Call (605) 376-2130 for same-day mobile service. We come to your location with the tools and parts to diagnose and repair brake fluid leaks on-site — no tow needed in most cases.
Prevention Matters
A brake fluid flush every 2–3 years removes moisture that corrodes seals and lines from the inside. It's one of the most affordable services we offer — and it prevents the most expensive brake failures. Get a quote →
Brake Fluid Leak — FAQ
Suspect a Brake Fluid Leak?
Free brake inspection at your location. We find the leak, show you what's going on, and fix it on-site.
(605) 376-2130 Get a Free Quote