6 Symptoms of a Bad Master Cylinder
Does your brake pedal feel spongy or like it’s sinking into the ground? If so, your brake master 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 rest assured, replacing a brake master cylinder isn’t as expensive as you might think.
Symptoms of a Bad Master Cylinder
1) Dirty Brake Fluid
The master cylinder has a rubber seal that wears out after a while. If the rubber seal is too damaged, the brake fluid will become dirty and black.
Another effect of worn rubber seals is that the master cylinder will not be able to withstand the braking pressure applied to it. As a result, the brake pedal will feel squishy and will slowly start to sink.
2) Sinking Brake Pedal
Normally, when you press the brake pedal, you will feel a somewhat firm and stable feeling. However, if the master cylinder is faulty, the pedal may gradually start to sink as you press it. 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 bad master cylinder. This is caused by air getting into the brake lines, making the pedal feel softer and less responsive than normal.
A small leak in the rubber seal in the master cylinder can allow air 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 braking problems. The first thing you feel when you step on the brake pedal is a soft feeling.
If there are no leaks and the brake fluid level seems normal, the master cylinder may be the culprit. The brake fluid in the reservoir should be sealed there and all hose connections should be tight and secure.
If you notice that your master cylinder is leaking and have checked for loose hoses, cracks in the reservoir, and leaking caps, replace the master cylinder as soon as possible.
5) Brake warning light
If 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) The engine check light is on
Many modern cars are equipped with a master cylinder that has 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 triggers 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 has been stored.
Note: If you’ve checked all the external components and found no signs of a problem, then the master cylinder is definitely bad. It may already be failing. Testing your brake system and looking for the symptoms above can help determine if the master cylinder or other component has actually failed.
