6 Symptoms of a Bad Master Cylinder
Does your brake pedal feel spongy and soft, or like it sinks into the floor? Then your master brake cylinder may be failing. Learn how this vital component works and how to recognize the most common symptoms of a bad master cylinder before your brakes fail completely. But don’t worry, replacing a master cylinder isn’t as expensive as you might think.
Symptoms of a Bad Master Cylinder
1) Dirty Brake Fluid
Brake master cylinders have rubber seals that wear out after a while. If the rubber seal is too damaged, the brake fluid will be contaminated and turn black in color.
Another effect of worn rubber seals is that the master brake cylinder cannot withstand the braking pressure applied to it. As a result, the brake pedal will feel soggy and will slowly start to sink.
2) Sinking Brake Pedal
Normally, when you press the brake pedal, you will feel a slightly hard and stable feeling. However, if the brake master cylinder is defective, you may notice the pedal gradually start to sink as you press the pedal. This happens because brake fluid is forced out of the system under pressure, indicating an internal leak in the master cylinder.
3) Spongy brake pedal
A spongy brake pedal is also a common symptom of a faulty master cylinder. This is caused by air getting into the brake lines, making the pedal feel softer than normal and less responsive.
A small leak in the rubber seal of the master cylinder can allow air to get into the brake lines, causing a spongy brake pedal and a less effective braking system.
4) Low brake fluid level
A low brake fluid level in the master cylinder can cause some issues with your braking. The first thing you’ll feel is a soft feeling when you put your foot on the brake pedal.
If there are no leaks and the brake fluid level seems normal, the master cylinder may be the culprit. The brake fluid in the container should be sealed there and all hose connections should be tight and secure.
If you notice that your master cylinder has a leak and you’ve confirmed that it’s not a loose hose, a cracked reservoir, or a leaking cap, replace the master cylinder as soon as possible.
5) Brake warning light
If you notice that the brake warning light is on on your dashboard, your master cylinder may be the problem. However, this light may also indicate other issues unrelated to the brake system. Therefore, to determine the exact cause, have your brake system inspected by a professional mechanic.
6) Check Engine Light Comes On
Many newer cars are equipped with a master cylinder that is fitted with a pressure sensor and a brake fluid sensor. These sensors detect if there is something wrong with the brake fluid pressure in your vehicle.
For example, if a loss of pressure is detected, the master cylinder is likely the culprit, and your car’s ECU will log a diagnostic trouble code that will trigger the “Check Engine Light” warning light on the dashboard.
If this light comes on, it could be the master cylinder. Of course, you won’t know the exact reason why your check engine light is on until you have your car scanned.
However, if the light comes on along with another symptom, it could be that there’s a problem with the master cylinder. Only with an OBD2 scanner can you determine what error code is stored.
Beware: if you inspect all external components and find no signs of a problem, your master cylinder is definitely defective. It may even have already failed. Testing your brake system and paying attention to the symptoms listed above can help you determine if the master cylinder or other component is actually at fault.