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How To Check Brake Caliper Piston?

Published by: Mark
Date of Publish:

A brake caliper piston is a component of the braking system in a vehicle that is responsible for slowing it down and eventually stopping it. It is the most important part of the overall brake system of the vehicle, and the piston is the main component of the brake caliper. For more about the brake caliper system, please refer to A guide to brake caliper system for automotive

The piston is responsible for enabling the brake pads to contact the brake disc, thus, slowing down the vehicle. When one puts their foot on the brake pedal, the pistons are pushed out behind the brake pads, which forces the pads to make contact with the brake disks, eventually slowing down the vehicle. When the foot is retracted from the pedal, the pistons retract into their housing.

Read on to know more about brake caliper pistons and how you can check for faulty signs. Later in the article, you will also learn about the problems in the caliper piston and the procedure for inspecting possible faults.

Faulty Signs Indicating Brake Caliper Piston Replacement

1.      Pulling Of The Vehicle To One Side While Driving Or Braking

One of the most prominent signs of a faulty brake caliper piston is pulling the vehicle to one side while driving or pressing the brakes. In case of a faulty piston, the brake pads will either not be able to release the rotor or will not come in contact with the rotor.

If the brake pads are unable to release the rotor, the vehicle will pull towards the side of the faulty caliper. In contrast, if the piston cannot come in contact with the rotor, the car will pull away from the faulty caliper. The pulling out of the vehicle can occur while driving or using the brakes.

2.      High-Pitched Squealing Sound

A high-pitched squealing or metal rubbing noise is never a good sign while operating a vehicle. If you hear a high-pitched squealing sound while driving your car, it is because of a fault in the brake calipers. On the other hand, if you hear the sound while using the brakes, it is because your vehicle’s brake pad is faulty.

Either way, you must take your car to a repair shop as soon as possible before the situation worsens and the brakes get locked up completely.

3.      Uneven Wearing Down Of Brake Pads

One needs to be quite observant to point out the fault in the brake caliper or the brake pads. If you notice the vehicle’s brake pads being uneven, it usually indicates a faulty brake caliper.

Uneven brake pads are thinner on one side and thicker on the other, and in case your vehicle has faulty brake pads, it should be taken to an auto repair shop immediately to fix the problem.

4.      Leakage Of Brake Fluids On The Ground

In modern brake systems, brakes are operated with the help of hydraulic pressure. If one notices an oily spot on the ground inside the tire, it usually means a leaking in the caliper.

In this case, it does not mean that the caliper is faulty, as leakage in the caliper can occur due to many reasons, and owing to that. One should get the vehicle properly diagnosed and repaired by taking it to an auto repair shop.

5.      Clunking Sound

A clunking sound is quite a less common faulty sign, but it does happen sometimes, and when it does, it usually means that the vehicle should not be driven any further. If you hear a clunking sound, the bracket that holds the brake caliper in place may be faulty.

While driving the vehicle, if the bracket is faulty or broken, it causes a loud clunking sound when used. In this case, the car should be taken to an auto repair shop as soon as possible, as it can cause severe injury to the driver because the brakes can get wholly locked up because of the faulty bracket.

The above tips can be seen more as a sign of the bad brake caliper itself. Please refer to how to know if you need a new brake caliper

How Caliper Piston Causes Calipers To Go Bad?

A vehicle's brake calipers can go bad or become faulty due to many reasons. One of the reasons for faulty brake calipers is a fault in the caliper piston. A caliper piston has a rubber boot or a rubber layer around it in order to protect and lubricate it and quite a few times, the rubber layer tends to tear which causes rust and other debris to slowly build up inside the piston.

In case the rubber layer around the caliper piston tears, the brake caliper may stick and can go bad. In this case, the whole brake caliper needs to be replaced with a new one.

Caliper Piston Problems

There are many reasons why a caliper piston can become faulty and may need a repair or replacement, like a stuck piston as mentioned in the above section. Hop on to the following points to learn more about the possible problems faced by a caliper piston.

Stuck Piston

In case you feel that the vehicle you are driving is fighting a counteracting force when being pushed forward, it may mean that the piston is stuck. Due to the tearing up of the rubber layer around the caliper piston, a rust and debris buildup occurs. Owing to the buildup of rust, the caliper piston can get stuck.

The main reasons for a stuck caliper piston are the inactivity of the vehicle and the corrosion. So, if you have a car that is lying idle for a long time, you may need to get it checked!

Lubrication Problems

A caliper piston can freeze due to the lack of lubrication which will cause it to go bad. The lack of lubrication is one of the primary reasons for a faulty caliper piston, as it leads to the wearing off of the caliper. Therefore, it is important to get your vehicle regularly lubricated for maintenance in order to prevent brake fluid from leaking out and to ensure that the brakes of the vehicle work properly.

Worn Out Piston

With time and consumption, a caliper piston can be worn out. It can be torn and cause debris buildup, which further causes excessive wear on the internal components of the caliper piston.

Did you know that corrosion is a caliper piston cancer? It can wear out the piston as well as the brake pads. To not let that happen, one needs to make sure to get their vehicle checked if signs of faulty pistons appear.

Caliper Piston Not Retracting Into Housing

Another problem related to the caliper piston is a faulty square-cut seal. A square cut seal is what allows the caliper piston to retract back into its housing. Though you can manually push the piston in, it is important for the proper working of the piston to be retracted into its housing by the square cut seal.

Some leading indicators of a faulty square cut seal are rapid brake pad wear, brake drag, or brake pull. A faulty square cut seal will result in the piston not being able to retract back into its housing which will lead to the brake pads maintaining contact with the rotor even when the brake pedal isn’t engaged.

Caliper Inspection Procedure

With the help of a friend, you can inspect the working of the caliper piston following any of the two given methods - a manual check or a check using a dial indicator.

Manual Check

Manually checking a caliper piston is a standard method of caliper inspection. It involves having a friend apply the brake pedal and noticing if the piston comes out of its housing. After that, the brake pads are to be used against the rotor.

Once this step is done, you need to have your friend retract the foot from the brake pedal in order to observe if the caliper piston retracts back into its housing. If the piston retracts by itself, the square cut seal is fine, but if the piston does not retract to its housing, it will indicate a fault in the fair cut seal, which will have to be fixed by taking your vehicle to an auto repair shop.

Check Using A Dial Indicator

Using a dial indicator in a shop setting is quite rare, but if you hook up the dial indicator to the caliper, you can physically measure its movement. Performing a dial indicator method requires a friend to apply the brake pedal lightly. Note that the brake pedal should not be applied down to the floor.

After completing the first step, the dial indicator should be used to measure the movement of the piston until it reaches 10,000-15,000, the friend needs to retract the foot from the brake pedal. If the caliper piston does not retract into its housing, it will automatically point towards the faulty square cut seal, and if the piston does retract, you need to measure its movement on the dial indicator.

On the dial indicator, you have the measure of the piston’s movement, which can indicate if the square cut seal is faulty or not. The square cut seal will not be faulty if the direction of the piston is measured anywhere between 4,000-6,000.


To conclude the article, a caliper piston is an essential component of a vehicle responsible for slowing down or stopping it. That being said, it becomes crucial to maintain the quality of the piston to avoid any injury to the driver.

In case of any faulty signs in the caliper piston, the vehicle should be taken to an auto repair shop as soon as possible. To check if the piston is faulty, you can either check the retraction of the piston into its housing manually or go for the dial indicator method.

How to check brake caliper piston

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