Brake Master Cylinder Buyer's Guide
- The brake master cylinder is at the heart of the braking system, which is where the brake fluid reservoir is installed on.
- It is a pipe-like component that distributes pressure to each wheel’s brake caliper cylinders.
- When the brake pedal is pressed, the push rod pushes 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 risk of road accidents. 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, which is made up of parts that are responsible for slowing down your car and bringing it to a full stop. At the heart of the braking system is the brake master cylinder, which is where the brake fluid reservoir is installed on.
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. It primarily consists of two piston assemblies controlled by a pair of circuit return springs. These pistons are known as the primary and secondary pistons, and each one has a respective chamber. 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?
The brake master cylinder transfers the pressure you put onto the brake pedal to make the brake calipers squeeze the brake rotor. 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 pushes 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. Here are the three common types of brake master cylinders:
This is the most basic type of brake master cylinder. 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.
A portless master cylinder provides brake release that's faster than a single and tandem cylinder. It works best for cars with an anti-lock braking system (ABS).
Symptoms of a Bad Master Cylinder
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, such as poor pressure distribution, could be a sign of a bad master cylinder. A fluid leak may also be 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. In some instances, the pedal might sink further down even after lifting your foot.
Longer braking distance
If you observe longer braking distances, it could be due to a lack of fluid being compressed by the master cylinder because of worn seals or a leak in the assembly.
Illuminated check engine light
Most modern vehicles have brake master cylinders with brake fluid pressure sensors. These are meant for detecting any problem faced by your braking system, especially the brake master cylinder. If an issue is identified, the check engine light turns on.
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 because you can't stop properly. A failing brake master cylinder increases your vehicle's braking distance and causes problems with your brake pedals.
Replacing a bad brake master cylinder lessens the risk of road accidents. It also ensures an optimum brake fluid level with fresh rubber seals, pistons, and return springs. If you notice 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.
When it's part of 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 a good option.
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. 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 an expert install the part properly but he or she can also check for problems in the other areas of your vehicle.
How to Replace a Brake Master Cylinder
If your mechanic confirms the need for replacement, check out this 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.