Brake Master Cylinder Buyer's Guide
- At the heart of the braking system is the master cylinder, which is where the brake fluid reservoir is installed on.
- The brake master cylinder is a pipe-like component that distributes pressure to each wheel’s brake caliper cylinders.
- When you press the brake pedal, the push rod presses the pistons through the linkage. This compresses the fluid in the chamber, which is then pushed through the corresponding brake lines.
- An aftermarket replacement brake master cylinder usually costs around $10 to $1,200 depending on the brand and type.
- A failing brake master cylinder compromises your vehicle’s driving safety by increasing its braking distance and causing problems with your brake pedals.
- Replacing a bad brake master cylinder lessens the chance of you rear-ending the car in front. It also ensures an optimum brake fluid level with fresh rubber seals, pistons, and return springs.
One important component in every car is the braking system. A car’s braking system is made up of various components. These parts are responsible for slowing down your car and bringing it to a full stop. At the heart of the braking system is the master cylinder, which is where the brake fluid reservoir is installed on. To learn more about your vehicle’s braking system, let us discuss its most important component—the brake master cylinder.
What is a brake master cylinder?
The brake master cylinder is a pipe-like component that distributes pressure to each wheel’s brake caliper cylinders. The brake master cylinder primarily consists of two piston assemblies controlled by a pair of circuit return springs. These pistons are known as the primary and secondary pistons with each having their respective chambers. The primary chamber receives brake fluid through the primary port, while the secondary port feeds the secondary chamber.
How does a brake master cylinder work?
In able for the brake calipers to squeeze the brake rotor, the brake master cylinder needs to transfer the pressure you put onto the brake pedal. The transfer of pressure is done with the help of the brake fluid and the master cylinder’s mechanism. When you press the brake pedal, the push rod presses the pistons through the linkage. The pressure compresses the brake fluid in the chamber, which is then pushed through the corresponding brake lines. The brakes are applied as the brake fluid reaches the brake caliper cylinders.
Types of brake master cylinders
Brake master cylinders come in different forms, sizes, and mechanisms, but all are designed to perform the same thing, which is to distribute pressure to the brake calipers. Here are the three common types of brake master cylinders.
This is the most basic type of brake master cylinder you could ever find. The inside of a single cylinder is identical to a medical syringe. The brake pedal is directly connected to the piston inside the cylinder. When the brake pedal is pushed, the piston move and compresses the fluid. When you release the pedal, the return spring expands and pushes the piston to its original position. There is only one piston and chamber in a single-cylinder brake master cylinder.
In contrast to a single-cylinder, a tandem master cylinder incorporates two pistons in one assembly. Only the primary piston is directly connected to the brake pedal. The primary piston pushes a spring from behind the secondary piston. The secondary piston will only push the fluid to its dedicated system once the springs are fully compressed.
To keep the pressure even on both sides, the reservoir inlet port allows fluid to fill the back of the pistons. When the brake pedal is released, a compensating port speeds up the springs’ expansion by filling the chamber with extra fluid as the pistons retract.
If you want to have at least one working brake subsystem in case the other malfunctions, this is a perfect choice to make.
Lastly, a portless master cylinder should be considered if you're looking for something that provides faster brake release than the other two aforementioned types of brake master cylinders. This type works best for cars with an anti-lock braking system (ABS).
Symptoms of a bad master cylinder
The brake master cylinder is the most important component of your car’s braking system. It is responsible for making your brakes fully-functioning. Making sure that this component is working properly could save you from having brake issues in the future. If you want to know how to tell if the master cylinder is bad, pay attention to these symptoms.
Spongy or mushy brake pedal
Unusual behavior on your brake pedal could be a clear sign of a bad master cylinder. The brake pedal tends to abnormally behave when the master cylinder’s poor and failing sealing or pressure distribution. There could be a fluid leak involved, which makes your pedal spongy, airy, or difficult to press.
Brake pedal not returning to its position
A spongy brake pedal is already bad as it is but a brake pedal that takes time before returning to its position is worse. This is a serious hazard because you are not in full control of your brakes. The pedal might sink further down even after lifting your foot in some instances. This could be due to return springs or clogged compensating port in the brake master cylinder.
Longer braking distance
If you observe longer braking distances, it could be due to lack of fluid being compressed by the master cylinder. Lack of brake fluid could be due to the presence of leak somewhere in the assembly or worn seals. Worn seals don’t hold brake pressure as good as a fresh seal. You also might feel mushy and spongy pedal along poor braking performance.
Illuminated Check Engine Light warning
Most modern vehicles’ master cylinders are installed with brake fluid pressure sensors. These are meant for detecting any problem faced by your braking system, especially the brake master cylinder. Any problem faced by the master cylinder could affect the entire braking system so make sure to bring your car to your trusted mechanic as soon as you begin experiencing some problems.
Importance of replacing a failing brake master cylinder
Without the brake master cylinder, your brakes won’t operate at all. Driving is extremely dangerous without brakes that are properly working because there’s nothing to stop the wheels from spinning. A failing brake master cylinder compromises your vehicle’s driving safety by increasing its braking distance and causing problems with your brake pedals.
Replacing a bad brake master cylinder lessens the chance of you rear-ending the car in front. It also ensures an optimum brake fluid level with fresh rubber seals, pistons, and return springs. If you experience something unusual with your brakes, replace them right away with the best-quality OE replacement parts from CarParts.com.
Brake master cylinder: individual master cylinder vs kit
If you're pretty sure that the brake master cylinder is the only thing that's damaged in your vehicle's entire braking system, then buying an individually-sold master cylinder is more reasonable and affordable. However, going for this option is a bit risky. During the installation, you might discover other parts to be worn out as well. This only means that you'll have to spend another visit to the auto parts store to get another part, which could have come with the brake master cylinder sold as a kit.
As a kit, a brake master cylinder comes with a reservoir and a bleeder kit. If you seek assurance and want to save time and effort in repairing your brake system, then the master cylinder kit is what you're looking for.
How much is a brake master cylinder?
An OE replacement brake master cylinder usually costs around $10 to $1,200 depending on the brand and type. OE replacement brake master cylinders are only sold individually. However, you can have them either with or without a brake fluid reservoir. If you’re out for an OE replacement brake master cylinder for your specific vehicle, be sure to input the year, make, and model to generate a list of perfect-fit components.
Although you can DIY-replace the brake master cylinder, we still recommend that you go see a certified mechanic. Not only can he or she install the part properly, an experienced mechanic will also recognize other problems involving neighboring components. Since the brake master cylinder is the heart of your braking system, adequate fitting is extremely important.
How to Replace a Brake Master Cylinder
Repairing the brake master cylinder cures two unwanted vehicle malfunctions: a leakage and/or a fading pedal. Check for symptoms by examining the firewall for leaks. If your brake pedal goes all the way to the floor when you hit the brakes, then that's a surefire indicator of a broken master cylinder.
Below is a step by step instruction on changing your master cylinder:
Difficulty level: Moderate
Things to be used:
- Owner's manual
- Turkey baster or an alternative suction device
- Brake fluid
- Line wrenches
- Phillips screwdriver
Step 1: Open the hood and locate the brake master cylinder. Refer to your car's manual if you're having trouble finding it.
Step 2: Look for the brake fluid reservoir and drain the brake fluid using a turkey baster or another suction device. However, if it's a two-piece master cylinder with a plastic reservoir, just detach the reservoir for reuse on the new master cylinder.
Step 3: Remove the electronic fluid level sensor, below the fluid reservoir, by disengaging and releasing the safety clip.
Step 4: Use line wrenches to disconnect the two brake lines from the brake master cylinder. Remove the two 15mm nuts to unbolt the brake master cylinder from the brake booster.
Step 5: Take the master cylinder out. Attach the bleeder hoses that came with the master cylinder into the holes for the brake lines.
Step 6: Using one hand, hold one end of the bleeder hoses in the reservoir. Refill the reservoir while pushing a Phillips screwdriver in and out on the plunger. This ensures that all air is out of the master cylinder and that the fluid flows to all of the ports.
Step 7: Mount the new brake master cylinder in a vice by sliding it on the brake booster studs.
Step 8: Replace and tighten the mounting bolts.
Step 9: Reconnect the brake fluid lines to the brake master cylinder. Return the electronic fluid level sensor to its place.