Updated at: 28-08-2022 - By: Lucas

What are the symptoms of a malfunctioning master cylinder? The brake system would be incomplete without a master cylinder. Your car’s brake system will not work if its master cylinder is faulty. When you wish to stop your automobile, you need to provide mechanical force to the brakes in order to get the hydraulic pressure from the brake clippers to pressurize the brake pads, thus halting your vehicle.

Despite its significance, a brake cylinder can malfunction. You and the individuals driving next to you are in grave danger if you find yourself in that situation. In order to keep you safe, it’s best to get your master cylinder checked as soon as possible.

It’s helpful to understand how the brake master cylinder works in order to fix the problem. In this article, we’ll go over six signs that your master cylinder is failing, as well as all you need to know about it. The first step is to familiarize yourself with the components of the master cylinder. You can tell whether your master cylinder is bad if you know how it works.

How Master Cylinder Works to Stop Your Moving Car

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The brake system consists of a number of interconnected and interdependent parts. The master breaker is vital because it transforms the energy delivered by the driver’s foot to the brake pedal. In order for this energy to go reach the brake pads, it must first be transformed into hydraulic pressure.

It forces the mechanical energy into the braking fluid, converting it into hydraulic pressure. The pressure is then transferred to the brake circuit, where it is used to bring the vehicle to a complete stop. Controlling how much braking fluid is delivered to the circuit is another function of your master cylinder. A master cylinder can be found with either disk or drum brakes.

Cars should also have two sets of brake circuits. The circuit’s pressure is generated by a tandem master cylinder. There are two separate braking systems that work together to ensure that even if one of them fails, the circuit will still function.

How To Tell If the Master Cylinder Is Bad

Bad Master Cylinder Symptoms

These are the signs of a master cylinder that has gone bad and has to be replaced. There are some instances in which a device may need to be replaced. As soon as you notice any of the signs listed above, you should have your vehicle inspected by a mechanic to ensure your safety on the road.

1. Warning Light

The first sign you’ll see on your dashboard is the warning light. In order to give the driver advance notice, the brake light will come on to serve as an alert. There’s something wrong with your brake system, not only the master cylinder, according to the warning message. Pressure is generated in the master cylinder whenever the pedal is pressed, and this pressure is used to push the cylinders’ pistons. To help your car stop, these motions are dispersed evenly throughout all of the brake components.

When a vehicle’s brakes are engaged, pressure is transmitted through the fluid. A sensor is located beneath the reservoir that holds the braking fluid and is linked to the dashboard of the vehicle. Its principal purpose is to determine whether or not there is always adequate braking fluid in the system. When the brake fluid level is low, a warning light is shown on the dashboard.

There are moments when it is not necessary to panic. There are times when the sensor malfunctions and sends out false signals. When this happens, make sure your mechanic thoroughly inspects it. If the light is coming from your master cylinder, you need to take quick action.

2. Spongy or Abnormal Brake Pedal

The brake system is controlled by the master cylinder. Pressing the brake pedal will make you aware of the problem if it’s broken. The master cylinder is either leaking or not transmitting pressure. The seals on the master cylinder will deteriorate with time, resulting in leakage.

As a result, pressing down on the brake pedal will result in a mushy, spongy, or sluggish sensation. When pressed, the brake pedal should always feel solid.

As a result, the pedal feels spongy since there is no movement caused by the action of pressing the pedal. It is highly likely that the master pedal has defective seals if you notice any abnormalities in the pedal’s action. In addition to a mushy brake pedal, air in the master cylinder might cause other problems.

Stagnant brake fluid is caused by air bubbles trapped between molecules of brake fluid. Spongyness can also be caused by damage to the braking lines and corrosion.

3. Uneven Brake Pad Wear

Your car’s pressure will not be delivered evenly to all four wheels if the circuit breaks. With the pressure applied, you’ll notice that only two of the four wheels come to a complete halt. When the master cylinder is defective, the brake pads wear unevenly. It suggests a problem with the master cylinder’s piston seals, which is the likely cause of the uneven pressure distribution. Also, a broken or leaking brake line can cause this problem. One side of the circuit will be faulty as a result.

The following are examples of how a malfunctioning master cylinder can cause problems:

4. Brake Fluid Leaks

You may have a leak in the master cylinder or the brake lines if your brake fluid level lowers. Below the braking fluid reservoir is the master cylinder. The valves in the braking circuits or the fluid control valve that takes the fluid to the reservoir and down to the master cylinder may leak.

Brake lines that have been damaged or rusted may develop leaks over time. When you look at the brake lines under your automobile, you’ll see the indicators of worn brake lines.

5. Contaminated Brake Fluid

The master cylinder has a rubber seal. Rubber seals that are worn or torn can make brake pedals feel spongy and allow brake fluid to become contaminated. In order to keep dirt, water, debris, and other foreign particles out of the braking fluid, the seal is expected to seal well.

The fluid’s hydraulic pressure will be messed up by these pollutants, making it extremely difficult to stop your vehicle. There are situations when contamination in the fluid slows down the process of stopping your vehicle. It takes some time for the pressure to have an effect on the wheels and bring them to a halt.

To avoid further damage, get your brake system, brake lines, master cylinders, and brake pads inspected by a mechanic as soon as possible.

6. Sinking Brake Pedal

When you step on the brake pedal, it should move down and up in a smooth motion while remaining firm. If you press the brake pedal and it sinks, you have a bad master cylinder. It’s a precise test for determining whether or not your master cylinder is functioning properly. Because it is pliable, the brake pedal should immediately return to its normal position after being released.

After pressing a skinning pedal, it will stay in the same place. This makes braking more difficult because it means the brake pedal will be closer to the floor. However, it can take a long time for some to return to their previous position, making it untrustworthy. Cars with sinking brakes pose a serious risk to drivers. Because you are unable to apply sudden braking pressure, you are always at risk. As soon as you see this, have your brakes checked out.

An ineffective brake booster causes these problems. Here’s a step-by-step method for troubleshooting brake master cylinder issues.

Simple Steps to Evaluate the State of Your Brake Booster

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If you’re on your own and curious about the condition of your master cylinder, follow these simple steps. Make the most of them to keep you and your vehicle safe at all times.

Park your car on a level ground

During the practice, your car should not roll away. Keep the handbrake engaged at all times.

Pop the hood and look under it

Rust and leaks in the brake lines should be looked for. As soon as they begin to exhibit signs of wear, they must be replaced.

Start your car to run your engine.

Allow your engine to run smoothly for roughly three to five minutes at a time. To see if there are any bubbles in the vacuum hose, spray it with soapy water. Leaks in the tube will be revealed by the presence of bubbles.


1. Can I drive with a bad brake booster?

No. Your passengers and other road users are at risk. Before you get behind the wheel, make sure the issue has been resolved.

2. Why is my pedal feeling spongy?

In some cases, the spongy feel can be caused by an out-of-date master cylinder. Your brake fluid should be inspected for foreign substances, such as air or leaking brake fluid.


An key component is a master cylinder If your brakes fail, you can’t go anywhere. To avoid a failed master brake cylinder and to be safe on the road, keep an eye out for the warning indications listed below.