Bad Master Cylinder Symptoms and Replacement Cost

Bad Master Cylinder Symptoms

The master cylinder is one of the most important parts of modern car models. It acts as the main valve which pushes the brake fluid right into the brake lines. With this process in place, the brake calipers may easily squeeze the pads on the rotors.

The master cylinder also works by pushing the metal rod right through the brake system and into the wheels. An end of the rod is connected to the pedal. It is activated as the pedal is in a depressed position. Typically, a bad master cylinder will create a number of symptoms that will serve as a warning to the driver that repair and service may be needed. The following bad master cylinder symptoms are the most common ones that you may encounter.


Six Symptoms of Bad Master Cylinder

1. Brake Warning Light is On

The moment that you step on the pedal for the brake, it works by pushing a rod in the master cylinder, which in turn, pushing the pistons inside the cylinder bore. This process also displaces the fluid, directing it right into the various brake circuits. The brake fluid enters the brake lines, and to the brake components found in the wheels.

One of the most obvious and the earlier symptoms of a faulty brake master cylinder is when the warning light is on. This is found on the dashboard. This indicator shows a reduction of the brake fluid pressure. One way in which you can isolate this issue is by putting brake fluid to fill the reservoir. This could one of these master cylinder leak symptoms go away. If it ends up happening again, there might an issue with the brake master cylinder or the possibility of leaks on the brake lines. 

2. Uneven Wear of the Brake Pad

Uneven wear of the brake pad is also one of the common signs of a bad master cylinder. This is often a result of a failed circuit, especially if just two out of the four wheels can apply the brakes. For instance, the right front side, along with the left rear side will be noticeably worn down more than the right rear and the left front.

A bad piston seal that is located in the master cylinder, or even a brake line leak may result in a failed circuit. Thus, if you observe uneven wearing of the pad, uneven braking, or noticing that your car leans to a certain side while braking, it could be caused by a faulty master cylinder. 

3. Faulty Brake Bias

The master cylinders of the brakes usually contain two different circuits that separate the wheels and brake fluid in pairs. The purpose of this design is to avoid a complete brake loss if there is a leak in a certain part of the system. Usually, these circuits work in controlling one front wheel, along with the opposing rear wheel.

If a circuit has failed, one obvious sign that you may see is your car pulling to one side when braking. This becomes even more obvious when you brake quite hard since the front brakes exert more effort in stopping the car than the brakes at the back. 

4. Sunken Brake Pedal

Aside from the brake master cylinder symptoms mentioned above, you may also observe the pedal not going back to the top after stepping your foot out of it. Rather, it sinks to the floor even more. This could pose a risk when driving, which is why it is very important to have the master cylinder fixed right away.

5. Brake Fluid Contamination

Another potential sign that could serve as an indicator of a bad master cylinder is brake fluid contamination. This comes as a result of the exposure to worn out rubber seals. These seals do not just help in keeping the fluid from oozing out, but they also stop debris and dirt from combining with the brake fluid and cause contamination.

When this happens, unfortunately, the pressure from the brakes will not be as strong as stepping on the pedal. This may require you to press down the pedal even harder in order to get your car to slow down. 

6. Spongy or Soft Clutch Pedal

If you observe that your clutch pedal feels easier to press or somewhat lighter than before, there might be an issue with the master cylinder. The reason? Compared with the nature of the clutch fluid, the air has a compressible characteristic. This means that if the air is present in the master cylinder of the clutch, the pedal will also begin to feel soft, even though there may seem to be no problem with the clutch.

One way to attempt to solve the problem is by bleeding the clutch. However, if you notice that the issue stays after some time, then the issue may really be with the master cylinder. It may need to be checked by a mechanic. 

Bad Master Cylinder Symptoms YouTube Video


The Master Cylinder Replacement Cost

If you are wondering how much to replace master cylinder, it is helpful to know that the average replacement cost of replacing a faulty master cylinder ranges from $250 to $550, especially if you are hiring a professional mechanic to complete the job, which is usually recommended at this point.

The actual cost of the master cylinder as well as its related parts, including the brake cleaner and the new brake fluid, usually cost around $320 or less.

At the same time, you also have to take into consideration the labor costs, which are around $250. Because the brake fluid is usually contaminated as the seal or the master cylinder fails, you will also require a bleed kit which will push the brake fluid right into the brake lines.


Final Words

It is usually difficult to ignore the bad master cylinder symptoms mentioned above and is not usually recommended to ignore them. If you have noticed any or all of the mentioned symptoms, then it is best to bring your car to a professional mechanic to have it checked, and to have the problem fixed right away, especially if a replacement is needed. 

About the Author JamesL Davis

James is a certified auto technician specializing in commercial vehicles. With 30 years of experience under his belt, James has encountered almost every type of automotive issue there is! Besides his day job at the repair shop, he is also an amateur race car driver.

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