Brake Fluid Leak: Top Causes and Symptoms to Know!

Many people, especially the new car owners, may not consider leaking brake fluid as something to worry about, but it has a severe impact on the overall brake performance. Brake fluid leak causes damage to the brake system, leading to brake failure and accidents. This matter requires immediate attention to ensure your safety and well-being on the road.

Learning what causes brake fluid to leak and leaking symptoms will surely aid in handling the situation in a better way.

Most Commons Reasons for Brake Fluid Leak

The first step toward how to fix brake fluid leak is to learn about the causes that prompt brake fluid leaking under middle of car.

Damage in the Brake System

Fault in the brake system, including brake lines or fittings, can cause brake fluid leak. Whether there is a hole in the brake lines or damage in the brake fittings – both have a negative impact on the brake system. Even it can reach a point when the brake stops working. It can lead to a life-threatening situation if not resolved immediately.

Faulty Master Cylinder

When there is a brake fluid leak under car, the defective master cylinder is usually the main culprit. However, slave cylinder issues can also be responsible for leaking with the fluid puddle under the car.

brake fluid leak under car
Be aware about puddle under the car. (Source: NU Brakes)

Loose Bleeder Valves

Bleeder bolts are the part of brake calipers. Its primary function is to remove excess fluid while servicing the other brake system components. Sometimes, the mechanic does not tighten the valves enough after brake fluid flush, and the loose valves can make the fluid leak.

Bad Wheel Cylinder

If any car with drum-style brakes has brake fluid on the wall of any wheel, a bad wheel cylinder is causing this. This is also a common reason for fluid leakage.


5 Brake Fluid Leak Symptoms to be Aware of

How do you tell if your brakes are leaking? Keep an eye out for these symptoms:

Brake Warning Light Turns On

Cars usually come with a warning light located in the instrument cluster. When this light is on, it indicates a leak in the braking system. Though this light can point out any brake-related problem, people often consider it as an early sign of fluid leak as low brake fluid is the main reason for most of the brake-related issues.

Fluid Puddle under the Vehicle

How to find brake fluid leak? If there is a small puddle under the car or there are fluid drops on or near the wheels, it’s likely to be a fluid leak issue. Leakage in both brake master cylinder and brake lines will leave drops of fluid underneath the car.

For some people, it becomes difficult to distinguish between brake fluid, transmission fluid, and motor oil. Remember that when new, brake fluid is clear or light yellow but the complexion darkens with time. Upon touching this oil, you will get a greasy feel and it smells like fish oil.

The final step is to check the car’s brake fluid reservoir. If that is not full, it must have a leak that you have to find out.

Unsatisfactory Brake Performance

Several issues can be responsible for poor brake performance and brake fluid leak is one of them. If the driver does not feel right about the whole car brake system, they should check the brake fluid reservoir immediately for the leak.

Squishy Brake Pedal

When you push the brake pedal to stop or reduce the car speed, it will go down only a little before becoming completely firm. But if the brake pedal feels soft or spongy, there are chances of trapped air in the brake lines.
Usually, the proper functioning of the brake line depends on it being full of brake fluid. In the event of a leak, air enters the brake line, making the brake pedals feel mushy. It can cause accidents when pressed down.

brake fluid leak symptoms
Spot brake is a symptom of fluid leak. (Source: Santeri Viinamäki / Wikimedia Commons)

Brake Pedal Sink

This one is almost similar to the earlier symptom and often occurs at the same time. When the leakage reaches a severe stage or the brake master cylinder starts having issues, brake pedals will go down all the way. It happens because the brakes cannot function without sufficient brake fluid.

Nonfunctional brakes are a direct threat to the passengers. Never drive a car if this symptom appears before starting the journey. If you notice this while driving, slow down using gears or emergency brake, and get off the vehicle after stopping it. get the car fixed before driving it again.


All the mentioned symptoms are grave, so don’t ignore any of them. No matter what symptom appears, check the car and fix the issue before driving. Although it is possible to diagnose a brake fluid leak from these symptoms, a mechanic is the best person for identifying and fixing these issues.