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

Tool and Supplies Needed

  • New brake master cylinder
  • Brake fluid
  • Line wrench
  • Show towels
  • Socket set
  • Protective gloves and eyewear
  • Soap and water



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.

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).

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.

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.