How To Replace A Brake Master Cylinder On A Car? { In 5 Steps }

The brake master cylinder is an important part of the braking system on a car that helps ensure the proper pressure and stability to press down on the pedal and apply brakes. When this seal begins to fail, it causes the pedal to sink to the floor as you attempt to apply brakes. To properly fix this issue, you must replace your master cylinder.

Replacing the brake master cylinder is not overly complex but does require some care and precision. You will need a C-clamp, bleeders, some basic tools like wrenches, and a few rags and towels for cleaning any spilled fluid quickly.

To best start replacing the master cylinder, there are two methods; bleeding it at a bench or on the car. It is always better to opt for bench bleeding since it takes less time and can be completed more easily without the concern of spilling fluid all over the engine bay. Dig into learning more about it.

Why does the Brake Cylinder Needs Replacement?

The brake master cylinder is an essential component of your car’s braking system and can often be the root of many problems. When the seal inside the master cylinder goes bad, it will allow brake fluid to escape, greatly decreasing your car’s stopping ability.

This can cause the brake pedal to sink, and a red warning light will appear on the dashboard. It is important to regularly inspect for any brake fluid leakage around the master cylinder, as this usually indicates that something has gone wrong and needs to be addressed immediately.

Additionally, suppose too much pressure is applied to the actuator rod and adjusted too far out. In that case, this can affect other parts of your vehicle’s braking systems. This extra pressure will not allow for the plunger inside of the master cylinder to retract fully.

It can cause residual pressure, which may result in breaking issues, such as your car rolling when you attempt to stop or lock up brakes at random intervals. If either of these scenarios occurs, you should replace your master cylinder immediately, as failure could lead to more serious damage.

How Do I It’s Time to Replace the Brake Master Cylinder?

If you notice excessive brake pedal travel, slow brake pedal return, or a sinking or spongy brake pedal, it could indicate a problem with your vehicle’s braking system. Additionally, if your brake fluid has turned dark brown or there is a constant low reservoir fluid level, these are signs of potential issues.

Cracked master cylinder housing or reservoir chambers may cause fluid loss; a leaking master cylinder can also contribute. It’s important to address these problems promptly to ensure the safety of yourself and others on the road. Regular maintenance and inspections can help prevent these issues from occurring in the first place.

Here is How to Replace a Brake Master Cylinder On A Car

Things You Will Need

Tools and Equipment
Floor jack and jack stands
Flat screwdriver or pry bar
Wrench set
Ratchet and socket set
New brake master cylinder
Appropriate brake fluid
Brake cleaner
Brake bleeder kit
Drain pan



Stepping one in a brake system repair identifies and accesses the master cylinder. To do this, the hood on the vehicle must be raised to access this critical component located on the firewall of the driver’s side. It is recognizable by its two or four brake lines connected to the main body of the cylinder and a small wiring connector attached to its brake fluid reservoir.

The proper operation of brakes depends on maintaining proper fluid pressure, so inspecting and replacing components within this system is essential for vehicles’ safe operation of changing master cylinders.

Experience may lead you to understand quickly how it works, or you could create a diagram to analyze its layout while also helping you determine what type of components will need to be replaced to restore full functionality and safety. Gaining familiarity with the master cylinder and its associated components will be valuable throughout your efforts in repairing brake systems.


The second step of removing a master cylinder is to drain any remaining brake fluid from the system. To do this, begin by unscrewing the cap at the top of the brake fluid reservoir carefully using your hand, being cautious not to allow any liquid to spill out.

Then, using a turkey baster or similar suction device, draw out as much of the old brake fluid as possible and then replace the cap.

The next step is disconnecting any electrical components attached to the master cylinder. Use a pair of pliers to release and pull away from the fluid level sensor in the reservoir.

Then, use a line wrench of suitable size (13-16mm) firmly secure them on the steel brake lines, twisting until those lines have been removed. This will allow you to free up access for the removal of both sides’ mounting bolts underneath found behind two threaded studs.


The third step in replacing a master cylinder is to reinstall it. Before installation, though, the new master must be bench-bled. This can be done by holding the master cylinder in a vise securely so that it does not move during the process.

From there, remove the fluid lid of the reservoir and the dust caps on both sides of the cylinder, which will cover the two line holes.

Next, take a master cylinder bleeder kit which consists of two or four plastic fittings and rubber hoses that connect to those fittings. The hoses should be routed back into their respective fluid reservoir lines.

These must be installed far enough into the fluid reservoir so as not to suck any air along with them; otherwise, this could result in air getting into other components throughout your brake system, causing excessive amounts of damage, depending upon how long it goes unnoticed.


Step 4 of the brake system replacement process requires bleeding the remaining brake system to ensure no air is in the lines. This is done by carefully draining out air bubbles trapped in the hoses and pistons, leaving only brake fluid. Once complete, the normal pedal operation should be restored, and any changes in overall brake performance should be expected.

Properly bleeding the brakes is a very important part of the process, as it ensures all gases are out of your braking system, reducing errors and increasing safety. It’s important to remember not to drive the car if you don’t feel safe or comfortable with your newly installed brake lineup, as even minor faults may cause severe accidents.

What If I Refused to Replace the Cylinder?

When a brake master cylinder is faulty, damaged, or contaminated and not replaced, the consequences can be dire. The most noticeable symptom of such an issue is a soft, low, or mushy brake pedal. If left unaddressed for too long, the entire braking system can fail, resulting in significantly longer than expected braking distances with an increased likelihood of a crash.

In the worst-case scenario, if your vehicle’s brake master cylinder fails while driving, you will have no brake pressure applied to the wheels. Fortunately, in this situation, you can still stop your vehicle by employing the parking/emergency brake via either a mechanical connection (if it exists) or an electronic button (in vehicles with electric brakes). And master cylinder repair cost may make you broke so it’s better to steps before it’s too late.

Once activated, press and hold the button until the brakes start to apply. It goes without saying that at this moment, it is key that everyone remains calm so that further accidents don’t occur.

How do I know if my master cylinder is bad?

Several signs can indicate a potential issue with your brake master cylinder. Here are five common symptoms that may indicate a bad master cylinder:

  1. Spongy or Soft Brake Pedal: If you notice that your brake pedal feels spongy, mushy, or goes to the floor with little resistance, it could be a sign of a failing master cylinder. This can occur when hydraulic pressure is lost in the braking system.
  2. Brake Fluid Leaks: Inspect the area around the master cylinder for any signs of brake fluid leaks. A leaking master cylinder can result in a loss of brake fluid, leading to reduced braking performance. Look for wet areas around the master cylinder or underneath the vehicle.
  3. Brake Warning Light: If the brake warning light on your dashboard illuminates, it could indicate a problem with the master cylinder. This light typically comes on when there is an imbalance in hydraulic pressure or a fluid level issue.
  4. Contaminated Brake Fluid: If you inspect the brake fluid and notice it appears dirty, contaminated, or discolored, it may be a sign of a failing master cylinder. Contaminated brake fluid can affect the operation of the braking system and lead to decreased braking performance.
  5. Brakes Dragging or Sticking: A faulty master cylinder can cause the brakes to stick or drag, even when you’re not pressing the brake pedal. This can increase friction, excessive heat, and accelerated wear on brake components.

If you experience any of these symptoms, having your vehicle inspected by a qualified mechanic is recommended. They can perform a thorough diagnosis to determine if the master cylinder is indeed the source of the problem and advise on the necessary repairs or replacement.

What causes damage to the master cylinder?

Several factors can contribute to the damage or failure of a brake master cylinder. Here are five common causes:

  1. Internal Seal Failure: The master cylinder contains internal seals that help maintain hydraulic pressure within the braking system. Over time, these seals can wear out or become damaged, leading to leaks and pressure loss. Factors such as age, heat, and exposure to moisture can accelerate seal deterioration.
  2. Contaminated Brake Fluid: Brake fluid is critical for properly operating the master cylinder and the entire braking system. Contamination of the brake fluid with moisture, dirt, debris, or air can cause corrosion or damage to the internal components of the master cylinder. It is important to regularly flush and replace the brake fluid according to the manufacturer’s recommendations.
  3. Overheating: Excessive heat can cause damage to the master cylinder. Continuous heavy brakings, such as during mountainous driving or towing, can generate excessive heat, leading to fluid boiling and potentially damaging the seals and other components of the master cylinder.
  4. Incorrect Brake Fluid: Using the wrong type of brake fluid can cause damage to the master cylinder. Each vehicle has specific requirements for the type of brake fluid to be used. Using incompatible brake fluid can lead to seal deterioration, internal corrosion, and reduced performance.
  5. Improper Installation or Maintenance: Incorrect installation or improper maintenance procedures can also contribute to master cylinder damage. For example, improper brake system bleeding can introduce air into the master cylinder, leading to decreased braking efficiency and potential damage.

Regular maintenance, including routine inspections, proper fluid replacement, and adherence to manufacturer guidelines, can help prevent damage to the master cylinder. If you suspect any issues with your braking system or master cylinder, it is advisable to have a qualified mechanic inspect and address the problem promptly to avoid further damage or potential safety hazards.

Can I drive with a bad master cylinder?

Driving with a bad master cylinder is strongly discouraged due to the potential risks and compromised braking performance it can cause. The master cylinder is a critical braking system component that generates and distributes hydraulic pressure to engage the brakes. When the master cylinder is faulty or failing, it can lead to various issues that jeopardize your safety on the road.

One of the main concerns with a bad master cylinder is a loss of braking power. A faulty cylinder may result in reduced hydraulic pressure, making it harder to bring the vehicle to a stop. Brakes may feel less responsive, requiring increased pedal effort and longer stopping distances. This can significantly impact your ability to control the vehicle, especially in emergencies.

Another problem associated with a bad master cylinder is brake fluid leakage. Leaks can occur due to internal seal failure or external damage. If brake fluid leaks out, it can lead to a decrease in fluid level, compromising the proper functioning of the braking system. Low fluid levels can result in spongy or non-responsive brakes, making driving unsafe.

Perhaps the most concerning consequence of driving with a bad master cylinder is the potential for brake failure. If the master cylinder completely fails while driving, it can result in a complete loss of braking ability. Without hydraulic pressure, the brakes won’t engage properly, leaving you unable to slow down or stop the vehicle. This poses an extreme safety risk to yourself, your passengers, and others on the road.

Frequently Asked Questions [FAQs]

1. Can You Change A Master Cylinder Without Bleeding Brakes?

Changing a master cylinder without bleeding the brakes is possible, but it is not recommended. Bleeding the brakes ensures that air bubbles are removed from the brake lines and the new master cylinder is properly filled with brake fluid. If you do decide to change a master cylinder without bleeding the brakes, it is important to make sure that there are no air bubbles present in the system before attempting to start or drive the car.

2. How Much Does It Cost To Replace A Master Cylinder?

The cost of replacing a master cylinder will vary depending on your vehicle’s make and model and the labor involved. Generally, you can expect to pay anywhere from $200 to $400 for a brake master cylinder replacement, with parts costing an additional $50 to $ 200. Labor costs can range from $80 to $250, depending on the job’s complexity and where you take your vehicle.

3. Is It Safe To Drive With A Broken Master Cylinder?

No, it is not safe to drive with a broken master cylinder—the brake master cylinder supplies pressurized brake fluid to the braking system when the brake pedal is pressed. A faulty or damaged brake master cylinder will cause a decrease in braking performance and can increase the likelihood of an accident.

4. How Long Do Master Cylinders Last?

The typical lifespan of a master cylinder is between 70,000 and 110,000 miles due to the wear and tear of its rubber seals. Failing to replace a faulty master cylinder can lead to a decrease in a vehicle’s braking ability.

5. Can A Car Run Without A Master Cylinder?

No, a car cannot run without a master cylinder. The brake master cylinder transfers the hydraulic pressure applied when the brake pedal is depressed to the brakes on each wheel. This hydraulic pressure causes the brakes to engage, slow, or stop the vehicle. Without this pressure being transferred, your car could not slow down or stop when needed.


It is important to replace a faulty or damaged brake master cylinder to ensure the safety of your vehicle. If left unaddressed, a broken master cylinder can increase braking distances and decrease the overall responsiveness of the brakes, leading to a higher likelihood of an accident. For this reason, you must follow proper procedures when replacing your brake master cylinder and always remember to bleed the brakes after the installation.

John D. Archer

John D. Archer is a mechanical engineer and writer based on the area of automotive accessories at, A resident expert and professional, John is passionate about all things automotive and loves to share his knowledge. He has good experience in all kind of automotive accessories. He has worked as a chief mechanical engineer in some reputed automotive garage firm.