Symptoms Of Bad Master Cylinder You Shouldn’t Ignore

The typical symptoms of bad master cylinder will help you determine its abnormal problems.

They indicate this part, which is an indispensable component in the vehicle’s brake system, is in the faulty status.

Also, your vehicle brake system cannot work without a poor master cylinder. It will ask you to make a thorough inspection to find the root cause and the best fix.

Thus, it is essential to diagnose the failures soon to keep your master cylinder in a good and safe condition.

This article shows the common signs of a faulty master cylinder with a detailed description and explanation. Besides, we also cover everything you need to understand about it.

Let’s read on!

What Is A Master Cylinder?

Symptoms Of Bad Master Cylinder

It is part and parcel in your vehicle’s braking system, driving the pressure the brake pedal generates to the braking system at your car’s wheels.

Pressing the brake pedal down will force the piston in the system through the braking cylinder. This process will convert the force in your engine system into hydraulic pressure.

Such a pressure can push the hydraulic fluid via the braking lines and transmits pressure to each wheel’s secondary cylinders at the braking mechanism.

The secondary cylinder drives the caliper piston, which engages the disc braking caliper (or drum braking wheel cylinder). This action keeps the automotive wheel stopped.

A master cylinder will work in the manual car’s clutch system, but it is different from the master cylinder.

Symptoms Of Bad Master Cylinder

Brake Fluid Contamination

illuminated Warning Lights

This is one of the standard master cylinder bad symptoms you should consider and check. When you find the brake warning light illuminated, you can understand your master cylinder is failing.

Since the brake master cylinder produces pressure, it will alert potential problems by turning on this light.

If this part gets a fault, the engine light will also come on. Thus, you must take your vehicle to an auto shop for a professional mechanic to diagnose the culprit and make a correct repair.

You must note that the master cylinder component is indispensable for your brake system to work properly. So, try to tackle unexpected problems before it becomes more terrible.

Spongy Brake Pedals

The brake pedals can be spongy since you depress them. This is one of the clear symptoms bad master cylinder.

If the master cylinder can’t generate the essential hydraulic pressure to brake the wheels of your vehicle, your brake pedal will act like a sponge.

One cause of this issue is a worn “rubber seal” on the master cylinder, which aims to keep the brake fluid inside the cylinder. They will leak and flood your brake pedal as they get worn out.

You should quickly search for a comprehensive automotive service in your area and hire an experienced professional to resolve your issue.

The master brake cylinder may be defective, or the lines with air inside may result in a spongy brake pedal even after bleeding. Rust, leaking calipers or faulty brake lines can also leave the pedals spongy.

Leaky Brake Fluid

You can overlook this symptom, but this is a serious cause leading to the bad master brake cylinder in your vehicle.

Brake fluid leaks need proper repair due to their negative impact on the braking system.

The vehicle master cylinder operates the automotive drums or brake calipers through brake fluid. So, if this part leaks with the brake line, the master cylinder will go bad.

Therefore, leaky brake fluid is among notable bad brake cylinder symptoms you shouldn’t skip. Look for this sign by observing the fluid drips in the right place under the brake master cylinder.

Besides, you can seek the leaky positions at the fitting connections between the brake master and the reservoir.

In this case, replace the brake master cylinder to avoid further affecting your car’s speed and performance.

Brake Fluid Contamination

One of the bad brake master cylinder symptoms is dirty brake fluid.

Damaged rubber seals in the master cylinder can contaminate the brake fluid. Debris will enter the fluid through holes in damaged rubber seals, contaminating it and reducing oil pressure.

If the oil pressure drops, the braking system will be unable to produce enough pressure and cause difficulty in stopping the car.

You should monitor your brake fluid to see if it has turned black or dark brown.

Aside from contaminating the brake fluid, a master cylinder, including worn seals, is less effective at retaining brake pressure, leading to slower bottoming or muddy pedals.

Low Fluid Level

Brake fluid levels in the master cylinder that are too low can also be one of the bad master cylinder symptoms. It first feels soft when you place your foot on the brake pedal.

If no fluid comes out and the brake fluid level is still normal, the master cylinder may be to blame. You must seal the brake fluid inside the reservoir and tighten the hose connection.

Inspect the fluid level if you have a doubt. To implement this inspection, place the master cylinder cap on the reservoir’s top and read the level on the side to ensure it’s not too low.

Abnormal Brake Pedal Behavior

The abnormal signs in the brake pedals also indicate you are using a faulty master cylinder.

These internal leaks often originate from utilizing a cylinder for a long time leading to the seals being worn out.

A faulty master cylinder will render the pedals slow, spongy, or mushy once pressed. The first thing you should note is that the brake pedal reacts abnormally.

Leaks can also continue if the cylinder’s seals keep wearing out. This will make the master cylinder cause spongy or muddy pedals.

A spongy pedal also means the brake line contains the air. And your vehicle may only need brake fluid replacement.

Uneven Pad Wear

You need to consider uneven pad wear if you can only brake 2 out of 4 wheels when driving your car due to a faulty electrical circuit.

Consider this symptom in the specific situation, which shows the right front and left rear sides to wear more than the left front and right back sides.

If the master cylinder’s piston seals fail or leak in the brake line, the circuit can also get a fault.

Suppose you detect problems, such as uneven pad wear, braking, or the car pulling to one side while braking. The master cylinder may be in trouble.

Thus, you shouldn’t ignore the uneven pad wear, as it is one of the critical brake master cylinder going bad symptoms.

The 3 mm thickness of brake pads is normally the point for replacement, so don’t let things go too far.

Brake Drag

Brake drag is also listed in the master cylinder failure signs. If you take your feet off the brake pedals, it happens when the brake pads can not release the automotive rotor.

Besides, hydraulic or mechanical problems can cause drag.

Mechanical problems comprise corroded or misaligned calipers, wrong wheel bearing installation, and improper push rod size.

Also, brake drag can come from the poor master cylinder with too much fluid.

If the liquid is too excessive in the cylinder, this reservoir will not have enough space for the inflow. This puts pressure on the caliper, so it doesn’t come off all the way.

Poor Brake Bias

Brake master cylinders include two circuits carrying the brake fluid to the automotive wheels.

These circuits often control one opposite rear and front wheel. Besides, the left front wheel and right rear wheel share an electrical circuit.

Or, the right front wheel and left rear wheel will have a distinctive electrical circuit.

If the circuit fails, your vehicle may pull to one side when you use the brake system. This issue is most noticeable if you find braking hard when the front brake does more to stop your car than the rear one.

This sign is poor brake bias, one of the master brake cylinder failure symptoms.

Sinking Brake Pedal

A sinking brake pedal is a common pointer of a poor master cylinder. A defective master brake cylinder can trigger the brake pedal to sink.

The master cylinder compresses brake fluid to generate hydraulic pressure, which activates the vehicle’s brakes.

When the master cylinder fails, it loses braking power and causes the brake pedal to sag.

In this situation, checking the master cylinder is your best bet, as sinking in the brake pedal is one of the master cylinder failure symptoms.

If you know to check a bad master cylinder in your car, you can try. However, you should take your vehicle to the auto shop and ask for a professional mechanic’s help.

No Brakes

In the worst case, the brakes may not work. This doesn’t occur often, but it can still happen.

The master cylinder acts as an essential hydraulic pump, pressurizing the brake lines whenever you press the brake pedal.

Losing the front or rear brakes becomes more popular with this design, but not both.

Yet, if the master cylinder fails, the brakes may not work at all. This is also one of the noticeable master cylinder symptoms.

Thus, you need to monitor whether your vehicle doesn’t brake or its braking system doesn’t function. Take the auto shop for automotive expertise to fix this fault quickly and properly.


The above are the popular symptoms of bad master cylinder you shouldn’t ignore if you want to give your car the best performance and safety.

When you fully understand signs that indicate your master cylinder gets problems, you can seek a quick and effective fix.

These symptoms can appear through strange warning lights, faulty brake fluid, brake pedal, or some other problems in your vehicle.

You need to identify the main reason for a bad master cylinder from these parts.

This is significant to support you in easily rectifying the root causes and avoiding dangerous driving accidents.

2 thoughts on “Symptoms Of Bad Master Cylinder You Shouldn’t Ignore”

  1. This did not answer any questions 4 new calipers 4 new flex hoses brake booster works 3 of of the 4 brake wheels get hot . Brake fluid is clean . The only thing could be is brake master cylender.Nobody can solve the problem


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