Five Signs That Your Brake Master Cylinder Is Not Working (& How Much It Will Cost to Replace it)

To keep the occupants of our vehicles safe, we need working brakes. However, there are so many parts to the braking system that could fail.

Breathing master cylinders are one of the most important components in the system. If one fails, serious consequences can follow. 

However, a bad brake master cylinder causes some odd symptoms that aren’t always simple to diagnose. Here’re some signs to look for:

A spongy, sinking or distorted brake pedal is the most obvious sign of a defective brake master cylinder. In extreme cases, you may notice a decreased brake power. It could be an indication of a bad brake master-cylinder.

Below is a list that explains the symptoms most commonly associated with a bad brake master-cylinder.

Bad Brake Master Cylinder Signs

1.An unusual Brake Pedal Behavior

At first, you’ll likely notice the brake pedal acting unusually. All of the brake pressure is generated by the master cylinder.

If there are any issues with sealing the pressure, or distributing it properly, the problem will be felt in the pedal. 

Leakages can also occur as the seals inside the cylinder wear down. That’s part of the reason that the brake master cylinder causes a mush or spongy pedal. Sometimes it may even travel to the floor. 

Sadly, this symptom alone won’t tell you that the master cylinder is bad. More often, a spongy pedal means there's air in your brake lines. It may be that your car needs to have its brake fluid changed.

2. Brakes that don't work

If the mastercylinder begins to fail, brakes could act in an unpredictable manner. One moment the brakes work perfectly, then the next you might lose all braking power. 

This is obviously a dangerous problem as it can be deadly if you don't understand how the brakes should work.

The pedal may feel firm at times and then drop to the ground the next. 

3. Reduced brake ability

The master cylinder can fail and cause brakes to stop working in one or both directions. You will experience a decrease in your braking power when this occurs.

As you prepare to stop, you aren’t counting on this extra time and you could end up getting into an accident. 

The same symptoms can be caused by malfunctioning components of your brake system. It could also be due to old or worn out fluid, air in the brake line. You may also experience these symptoms if your brake line is damaged or the hose has burst.

4. There are no brakes

Sometimes, in severe cases, brakes might stop working at all. While this doesn’t happen often, it is possible. 

As a hydraulic pump the master cylinder continuously presses the brake lines whenever you press the pedal. It is more common for brakes to fail at the rear or front of this system, but it does not happen in both. 

If the master cylinder is damaged, however, your brakes could be completely deactivated. 

5. Leaking Fluid

You should inspect the system for brake fluid leaks. There may be a leak in the brake fluid from behind the master cylinder to the firewall.

The firewall may be visible as brake fluid runs down inside your cabin. This can eventually cause your brake system to lose its fluid.

You will notice that the fluid is leaking more often, and you'll also start to feel the sponginess in your pedal. While it might regain some firmness when you pump it, it won’t last for long until a repair is performed. 

RELATED : 5 Signs that your Brake Fluid Leak is a Problem

What is the Function of a Brake Master Clider?

As a hydraulic pump, the master cylinder also acts as an actuator. This cylinder is responsible for supplying brake fluid to brake circuit. It converts pressure from brake pedal into stopping force. 

The master cylinder can be thought of as a syringe. When pressure is applied to this master cylinder, fluid pushes from the cylinder towards the brakes. 

Modern master cylinders have two chambers that each operate one set of wheel. This design means that you can only loose brakes at the front and not in either of their backs when there is a problem. 

The master cylinder has a reservoir that stores brake fluid. The brakes function by allowing fluid to flow into the lines of the master cylinder when they are applied. 

The fluid is released from the reservoir and the wheel can move again after it has been released. 

Brake master cylinder location

Under the brake fluid reservoir is where you will find your brake mastercylinder. To find it, look under the hood on the driver’s side of the vehicle. 

It's usually located on the firewall. It is usually located on the firewall. It’s also attached to the brake fluid reservoir with a small wiring connector. 

Repair of Brake Master Cylinder

Replacement costs for brake master cylinders range between $250-$400. When replacing the mastercylinder, you have two options. There are two options when it comes to replacing the master cylinder. You could either buy a brand new one or a rebuild.

Because of how important the braking system is to your safety, it’s often recommended to choose a new master cylinder. On average, a new master cylinder will cost between $35-$75 depending on which car you have. Labor at the local shop is what will add the rest to the cost. 

If you plan to do it yourself, you don’t need any specialized tools. The brake fluid will cost $4 more and the required bleeder kits, $10 less.