Symptoms of bad master cylinder

Symptoms of a bad master cylinder

The master cylinder is one of the vital parts of a vehicles braking system. It is responsible for the conversion of the pressure that you put on your brake pedal to hydraulic pressure. Any problem with the master cylinder automatically means a problem with the entire braking system of your vehicle.

Once the brake master cylinder of a vehicle starts to go bad, there are certain symptoms that will arise. This guide will show you how to easily identify the symptoms of a bad master cylinder.

How Does A Brake Master Cylinder Work?

The Brake Master Cylinder works by turning the pressure exerted on the brake pedal (by the driver) into hydraulic pressure. The  Brake Master Cylinder does this by supplying the break circuit with brake fluid.

The Master Cylinder is also responsible for managing the amount of brake fluid that flows into the brake circuit based on the pressure applied on the brake pedal. 

Every vehicle is required to have two different braking circuits. This is to ensure that there is a continuous functionality of the braking system in case one of the braking circuits stops working.

So whether your vehicle uses drum brakes or disc brakes, it is equipped with tandem master cylinders that are responsible for generating the hydraulic pressure needed by the circuit. 

What are the symptoms of a bad master cylinder?

Some of the general symptoms of a bad master Cylinder Include:

  • Irregular Brake Pedal Behavior
  • Contaminated Brake Fluid
  • The Brake Warning Light Comes On
  • Brake fluid leak
  • Sinking Brake Pedal

1. Irregular Brake Pedal Behavior

One common feature of bad or failing master cylinders is the exhibition of an abnormal pedal behaviour. This is usually the first thing to be noticed. The brake pad or pedal should normally feel firm when pressure is applied to it (depending on the force applied to it). However, if there is a problem with the master cylinder, you might experience a spongy feeling when pressure is applied to the brake pedal.

The master cylinder is responsible for generating the requisite pressure needed for the braking system to work and if it encounters a problem with pressure distribution, this may be felt in the brake pedal.

One of the major causes of a spongy brake pedal is the wearing out of the rubber seals contained in the cylinder. These seals help to keep the fluid within the cylinder and if they get damaged or worn out, it can result in an internal leak.

Another cause could be the presence of air in your vehicle's brake lines. This prevents the brake fluid from flowing in an efficient manner.. Damage to the brake lines and rust can also cause a spongy feeling when pressure is applied to the brake pedal.

What are the symptoms of a bad master cylinder

2. Contaminated Brake Fluid

Another thing that you might notice when you have a bad master cylinder is a contamination of the brake fluid. 

When the rubber seals contained in the master cylinder get damaged or worn out, it can lead to contamination of the brake fluid. This is because the rubber seals do not only keep the brake fluid from leaking, they also prevent debris and dirt from mixing with the brake fluid. 

If these particles mix with the brake fluid, they tend to reduce the hydraulic pressure and you may find it more difficult to stop the car.

3. The Brake Warning Light Comes On

This is the easiest symptom to notice. When this light comes on, it indicates that there is a problem with the braking system. This does not necessarily mean that the brake master cylinder is at fault as there are many other reasons why the light can come on. It is however one of the ways to know when the cylinder is faulty or bad, especially when some of the other features in this list are exhibited.

At the base of the brake fluid reservoir is a sensor that monitors the fluid level in the reservoir. If there is a drop in the fluid level this sensor will share the information with your car which will in turn trigger the light.

A low level of brake fluid triggers this indicator so if you notice that you are constantly topping your brake fluid, it means that there is a leakage somewhere and you should have your brake master cylinder checked.

4. Brake Fluid Leak

Anytime you fill your reservoir with brake fluid, it goes straight to the master cylinder. This is because the cylinder is responsible for the supply of the brake circuit with brake fluid. 

The master cylinder can be found at the base of the brake fluid reservoir and can be easily inspected for leaks. Any sign of a lk might indicate a problem with the brake master cylinder.

5. Sinking Brake Pedal

This is a clear indication of a bad master cylinder. Typically, when pressure is applied to a brake pedal, it should return to its normal position immediately you stop applying pressure. However, when you have a sinking pedal, the pedal stays down when you stop applying pressure and does not return to its normal position.

In some cases, it goes back up but it does this really slowly.

If you have a case of a sinking pedal, you should NOT drive the car as it is very dangerous. Driving the car will put yourself and other occupants of the car as well as other road users in serious danger.

You should get a mechanic to check this problem as soon as possible.

Symptoms of bad master cylinder

How much will it cost to replace a bad master cylinder?

It will cost you between $250 and $550 to replace a bad master cylinder.It is highly recommended that you get a professional to replace it for you.

If you however have good knowledge of vehicles and braking systems, you can easily save a fortune and replace it yourself. 

If you happen to experience any of the symptoms listed in this article, make sure you attend to it IMMEDIATELY so you don't put yourself and other people in serious danger.

Can I drive with a bad master cylinder?

You should never drive with a bad master cylinder. This is very dangerous and can cause serious harm not only to yourself but also to other people. Get the car to a professional immediately.


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