Master Cylinder: Everything You Need To Know

Do you feel the urge to know more about the master cylinders so you could be confident to fix them on your own? Worry no more because, in this article, we will bring out every single important detail you should not miss!

Generally, a master cylinder is a stopping mechanism that is responsible for the overall braking process. This is stimulated by distressing the brake pedal, thus, it is intended to serve the most important function for any vehicle. It injects brake pads into the braking system to transform the force on the pedal to hydraulic pressure.

Peruse the entire thing to recognize how the master cylinder functions, what it does for your disc brake, how to identify issues with it, and the simplest option to have your brake repairs done.

What Is The Master Cylinder?

A master cylinder is believed to be the heart of any vehicle’s braking system. This is responsible for transferring the pedal’s intense levels to the mechanism at the tires.

Specifically, this is a water-powered device wherein the plugs and coils are placed in order, allowing the mechanical energy connected to the automobile’s pedal by the operator. While, for motorbikes, this allows the switch to be transformed into a water-driven pack which is later used for deceleration by the caliper.

Brake master cylinder and brake lines.

Typically, these are made from aluminum or cast iron. When you apply pressure to the brake, the energy urges a piston through the cylinder, transforming the power into hydraulic pressure.

This pressure forces hydraulic power through the brake system, sending a force to a backup cylinder for every car’s brake system. In drum brakes, the backup cylinders push the caliper piston, which engages the calipers. This then causes the motor to come to a halt.

There are five types of master cylinders such as open, closed, single, ported tandem, and portless. Although they are all different, one thing remains true for all master cylinders; they are intended to make the vehicle’s life however, they can seep and screw up, necessitating its rebuilding or replacement.

How Do Master Cylinders Work?

The majority of master cylinders are tandem, also known as dual master cylinders. Two cylinders are merged within a closed position for the tandem master cylinder, unifying the cylinder bore. The cylinder structure can thus regulate two distinct hydraulic wirings. Each one of these circuits is in charge of a pair of brakes, front, rear, or diagonal circuit configurations are most common to see.

As a result, if one of the brake circuits screws up, the other circuit, which regulates the other pair, can bring the car to a halt. For most automobiles, a tolerancing piston connects the master cylinder to the entirety of the brake. It modulates the pressure difference on both the front and rear brakes, resulting in equitable, dependable vehicle performance.

The reservoir for the master cylinder is situated at the top of the master cylinder. To preclude the airflow into the brake system, it must be appropriately packed with hydraulic fluid.

If you’re wondering what will happen to the master cylinder once you pressurized the pedal, consider the following:

  • To begin, a pushrod will be used to drive the primary piston, which will compact the brake fluid in its switch.
  • The hydraulic pressure within the cylinder and brake lines rises as the primary piston shifts.
  • The secondary piston will then be driven by this pressure which will result in condensing the brake fluid in its loop.
  • The braking mechanism will be activated as the brake fluid flows through the brake lines.
  • So when you let go of the pedal, the coils will revert each piston to its original position.
  • Lastly, this will absolve the system pressure and disconnects the brake pedal.

How Does the Master Cylinder Influences Braking Performance?

The master cylinder bore diameter has a significant impact on the braking performance. A certain adjustment in its diameter will influences how the pedal makes it feel to you as well as the amount of pressure you apply.

In particular, if the cylinder bore diameter is too big, it will produce a pretty tough pedal, requiring more initiative to push the pedal. It will also provide a tight stroke, indicating that the pedal will not transport further to produce adequate brake force. As a result of the high resistance, you may eventually wind up with a jittery vehicle and you’ll have to hit the brakes tight, making the brakes connect too quickly.

If the cylinder bore size is very small, it will have a gentle pedal, which requires minimal effort to push. It will also lead to a longer stroke, in which the brake must be squeezed down to generate braking force. Therefore, there would be less tension on the brake, but you will have to push down harder to get the brake pads to operate. This is not a good scenario if you are stuck in traffic or you need to make a quick stop.

It is also vital to recognize that master cylinders for drum brakes are generally smaller since drum brakes demand only a little force, and a one­way residual release valve is commonly used in them. This valve maintains a light touch for each brake line, allowing the disc brakes to connect more quickly.

Now that you acknowledge how well the master cylinder performs and why it is so crucial for the braking performance, your next question might be how to tell whenever the cylinder fails.

If that’s the case, don’t worry, we’ve got you covered!

How to Spot A Bad Failing Master Cylinder?

Provided below are some common issues of a bad brake master cylinder. Take note of them as these will help you be more guided in determining whether you need repair or not.

1.     Brake Fluid Leaks

If you notice a leak of fluid under your car, it’s a clear indication that something is bad. If this occurs, let your mechanic inspect the brake fluid reservoir immediately. Even a simple leak can cause the brake liquid pressure to fall, and a significant drop in it will jeopardize the efficiency of your brake system as well as your safety on the highway.

2.     Contaminated Brake Fluid

Brake fluids should be clear or golden yellow to brown in appearance. Something is also wrong if you observed that your brake fluid is turning into a dark brown or black. If your brake pads aren’t working properly, a rubber gasket of your master cylinder may have stretched out and degraded. This is where contamination takes place in your brake fluid, thus, it also needs inspection by a mechanic.

An auto mechanic pours brake fluid into the car.

3.     Unusual Brake Pedal Behavior

If there are any serious problems with the hardening or pressure allocation of your master cylinder, your brake pedal should indicate it. However, if you sense a crumbly pedal that lacks opposition and drains gradually to the ground when squeezed, this is an indication that the master cylinder is faulty.

In some cases, the brake may not return seamlessly to its original position once you extract your foot. This is generally caused by problems with your brake fluid pressure which is induced by a faulty brake master cylinder.

The same with the latter, take your car to the mechanic if your pedal momentarily begins to act strangely.

4.     Weaving When Braking

As indicated above, to transfer the brake fluid to two distinct pairs of tires, the brake master cylinder requires at least two separate power circuits. When braking, whatever malfunction in one circuit can end up causing the vehicle to slide to one side. Thus, it also needs immediate action.

5.     The Engine Light Or Brake Warning Light Comes On

In modern cars, the master cylinder may contain brake fluid levels and stress detectors. These will discern and alert you if there is a sudden drop in hydraulic pressure. As a result, if your turbine or master cylinder warning light illuminates, do not disregard it. It may be an indication of collapse or malfunction, especially if it is supported by any of the foregoing signs.

Brake warning light displayed on car’s dashboard.

6.     Uneven Wear In Brake Pads

If either of the master cylinder’s circuits fails, the disc brakes will wear unevenly. Whenever you stop, each pair of disc brakes will wear out more rapidly than another and it will cause your car to meld.

How Much Does a Master Cylinder Repair Cost?

The estimated price of a brake master cylinder repair and replacement ranges from approximately 230 to 750 dollars, depending on several factors. The manufacturer of your car will determine the majority of the cost estimation since it specifies the expenses of the items needed.

To give you some specifics, the prices for some popular brands are listed below.

  • Chevrolet Silverado is between $300 and $545
  • Ford Focus is between $400 and $750
  • Toyota Camry is between $310 and $530
  • Honda Civic is between $230 and $475

Since a lot goes into the procedure, a master cylinder replacement is normally among the most expensive brake servicing. It entails unplugging the brake booster and brake pads, removing the old master cylinder out from the router, setting up a new master cylinder component, reuniting the brake lines and booster, and emptying the brake pads of old liquid and air.


Without a doubt, master cylinders play the most important role in a vehicle’s braking performance, so learning everything you can about them should be a top priority. You can protect the entire braking system if you are well-versed in its functions, capabilities, and potential issues.

If you have any questions, we would appreciate it if you could leave them in the comments section below.

Furthermore, this demonstrates that master cylinders are at the heart of the entire braking mechanism. Depending on how you care for them, they will continue to either improve or degrade overall performance.

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About Matthew Webb

Hi, I am Matthew! I am a dedicated car nerd! During the day, I am a journalist, at night I enjoy working on my 2 project cars. I have been a car nerd all my life, and am excited to share my knowledge with you!

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