The caliper piston, or brake caliper piston, is one of the most important parts of the braking system. You’ll learn about its function, common symptoms, and more in this guide.
The brake caliper piston is located inside the brake caliper. The caliper piston is the component responsible for pushing the brake pads into contact with the braking rotor.
When you press the brake pedal, brake fluid is pumped from the master cylinder into the brake caliper, where the caliper pistons push the brake pads into the brake rotors. The friction generated between the brake pads and the brake rotor turns mechanical energy from the wheel into heat energy. This slows the rotation of the wheel, effectively slowing the vehicle down. When you lift your foot off the brake pedal, the pistons, and therefore the pads, retract due to a drop in braking fluid pressure. A part called the square cut seal also helps pull the piston back off the pads.
A single brake caliper can contain one, two, four, or six pistons, depending on the vehicle and application.
The pistons of brake calipers can be made from plastic, steel, or aluminum. Although aluminum is lightweight and steel is strong, aluminum can transfer too much heat to the brake fluid, causing brake fade. Brake fade is when brake components become too hot and result in decreased braking performance. Additionally, both steel and aluminum can corrode over time.
A brake caliper tool is designed to assist mechanics to install a new set of brake pads. The tool pushes the caliper pistons back so you can install a new set of brake pads and put the caliper back onto the brake rotor.
Brake caliper pistons are typically tough and durable. They can handle immense fluid pressure from the master cylinder and the heat from braking. They’re also regularly exposed to elements like dirt, water, and debris. Brake caliper pistons can last for years.
However, calipers and caliper pistons can corrode since they’re made of metal. The caliper pistons won’t extend or retract smoothly in the caliper if they’re rusted. Rust buildup can be more prevalent in areas where salt is present.
Caliper pistons can get stuck in a retracted position and be unable to engage the brake pad onto the brake rotor. Conversely, the piston can also get stuck against the rotor and wear down the brake pad or damage the rotor. If the caliper pistons get stuck, they typically need to be replaced.
Some pistons are also made from a material called phenolic resin. These types of caliper pistons can crack because of age or if they’re depressed back into the calipers improperly.
A faulty brake caliper piston can be one of the culprits of a faulty brake caliper. The caliper piston has a rubber boot around it to protect it from the elements. If the rubber boot tears, then the piston will be susceptible to rust and damage from debris. When the caliper develops issues, your vehicle can exhibit the following symptoms:
Hydraulic pressure from the master cylinder moves the brake caliper pistons in and out. If the pistons seize because of debris or rust, the brake pads will either fail to release themselves from the rotor or will fail to push on the rotor. If the pads get stuck in an engaged position, the vehicle will pull to the side with the damaged caliper. If the brake pad isn’t making contact with the rotor, then the car will steer away from the faulty side. Either one of these issues can occur whether or not the driver is pressing on the brakes.
A screeching noise coming from the damaged caliper is another sign of a stuck or frozen brake caliper. A faulty brake caliper piston can make a noise even when the driver isn’t pressing on the brakes. If this happens, take your vehicle to an auto repair shop as quickly as possible since a frozen or blocked caliper can cause the brakes to totally lock up.
If you hear a high-pitched noise without pushing on the brake pedal, then that might be the brake pad warning device or a squealer, which is meant to warn the driver when brake pad thickness is low.
If the brake pads on one side of the brake caliper appear to be thinner than the other, the braking caliper pistons might be the problem. The caliper piston might not be applying even pressure onto the brake pads. Alternatively, it could also be a part called a caliper slide that isn’t allowing the other caliper to slide away from the rotor.
Hydraulic pressure is used to operate modern braking systems. When a leak develops, drivers might see oily fluid accumulating under their vehicle. However, this fluid might come from other brake components like the master cylinder or fluid lines. Consult with a trained mechanic to properly diagnose and repair the problem.
It always pays to be safe, which is why you shouldn’t compromise when it comes to replacing damaged brake parts, including the brake caliper piston. Keep your vehicle’s braking system in tip-top shape when you replace its damaged or worn-out brake caliper piston with a new one from CarParts.com.
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Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.