Changing your vehicle’s brake pads is part of the routine maintenance schedule. As the brake pads wear down from use, the piston in the rear brake caliper can move out more to keep the brakes working effectively.
But when it’s time to change the brake pads, you will need to push the piston back in. Compressing the brake piston of the rear disc brakes is possible with or without the brake caliper rewind tool.
If you don’t have the brake piston caliper tool, you can use a screwdriver or pair of pliers to push back the brake piston. Since the piston is threaded, you will have a tool that can wind it back like a screw into the caliper.
Keep reading our detailed guide as we answer how the brake piston comes out of the caliper, how to retract it without a tool, and what to do when it refuses to compress.
Why do the brake pistons extend?
It’s important to know how the brake pistons work to understand why they come out of the caliper. Brake pistons are a key component of the brake calipers and essential to the overall braking system.
You will find the rear brake caliper over the brake pads/ rotor; when you apply pressure to the brakes, the caliper compresses over the brake pads.
Depressing the brake pedal pushes the brake fluid from the master cylinder through the brake lines and into the brake caliper. Then the brake fluid inside causes the caliper to push the pistons out behind the brake pads.
As a result, the brake pads will make contact with the brake disc, causing friction between the rotor and brake pads bringing the car to a halt.
Every time the brake pads make contact with the rotating disc, they wear down, and the effectiveness of the pads reduces. This causes the brake piston to come out from the caliper. Because of this, the brake pads will need replacing.
However, replacing the brake pads might be difficult because the caliper piston has fully extended. So you will have to reset the piston back into the caliper to remove the worn-out brake pads properly. You can perform this task with or without the caliper rewind tool.
Can you push the brake caliper piston by hand?
You will not manage to use your bare hands to push back the caliper piston since it is threaded like a screw. Therefore using your bare hands will be too difficult to screw it back in.
However, you can use pliers, a screwdriver, or a caliper piston compressor to successfully push back the brake piston to allow you to change your brake pads.
Ideally, you will need a special brake caliper tool to retract the pistons back into the caliper. But if you don’t have this tool, this article will guide you on compressing the brake piston without a tool.
What can I use instead of a brake caliper piston tool?
You can use several tools to push back the brake piston if you don’t have the rear brake piston tool. They include:
- Flathead screwdriver
- Pliers
- Old brake pad
- Dowel
Once it’s time to change your brake pads, follow the detailed steps below to push back the brake caliper piston without a tool.
Locate the piston
- First, you need to find the rear brake piston. The brake piston is in the interior brake part of your vehicle.
- Then loosen the lug nuts on the wheels but not completely.
- Use a jack to raise the car.
- Once the vehicle is secure, remove the lug nuts and the wheel assembly to get to the rotor and calipers.
- Open your car’s hood and remove the brake fluid tank cap. You will have to regularly check that the brake fluid doesn’t overflow as you tighten the piston into place.
- Loosen the brake line and detach it from the caliper, then place the sealing washers and banjo belt aside. Ensure the brake fluid doesn’t leak from the brake line using a brake line hose plug. Be cautious with the brake fluid as it is corrosive and harmful if it comes into contact with the skin.
- Remove the bolts on the caliper and rotating disc. You should be able to locate the caliper and its location in the vehicle.
Remove the caliper piston.
- Detach the caliper from the rotor. Remove the mounting bolts on the caliper the remove the caliper from the rotating disc. You can remove the piston caliper by pulling it up by hand or using a screwdriver.
Push back the piston
- First, you need to note that you cannot move the rear piston the same way you move the front caliper, as you will cause more issues.
- Look for any of the tools mentioned above or any other tool that can fit into the caliper and gently rotate the piston without causing damage.
- Put your tool of choice into the caliper and turn the piston clockwise. The piston will start retracting back into the housing inside the caliper. Continue turning until the piston and seal are flush inside the housing.
Turn the brake caliper.
- Turn the caliper so that you can remove and replace your vehicle’s brake pads.
- Reattach the caliper and bolts back, then replace the wheel and lug nuts.
- Reconnect the brake line, check the brake fluid level, and add more if necessary. Finally, recap the brake fluid container and close the hood.
It’s important to note that using standard tools like pliers or screwdrivers to push back the caliper can damage the piston or caliper if not used carefully. You might even sustain slight injuries in the process. To avoid these issues in the future, you can invest in the right brake caliper piston tool.
Rear brake caliper piston won’t compress.
The most probable reason the caliper piston won’t compress is that a defective piston boot leads to a corroded or rusted caliper piston. However, occasionally, it could be due to the wrong wind-back process. Here are the details on all the possible reasons why your rear brake caliper piston won’t compress.
Corroded piston
A damaged caliper piston boot will lead to the corrosion of the caliper piston. Therefore the corrosion will prevent the brake calipers from operating correctly or cause a rubbing noise from the front wheels when driving. Note that even minute traces of rust have impeded its ability to compress.
Thankfully, this is not a common issue if you are an active car user. On the other hand, leaving your vehicle idle for months will create the best conditions for rust to thrive. Also, driving on wet or salted roads can lead to corrosion, especially if the boot is slightly damaged.
Worn seals or boot
It’s normal for piston seals to wear out over time. However, ultimately the seals will wear down completely, causing the piston to seize.
The caliper bolts also have rubber boots that protect the piston and keep it lubricated. However, as the rubber boots deteriorate, water can also enter the piston and cause it to get seized.
Defective brake hose
If the brake hose breaks or cracks, the brake fluid flows onto the piston. And since the fluid can’t flow back to the master cylinder, the caliper becomes stuck.
Contrarily, sometimes the piston is not the one stuck. In other cases, a damaged brake hose could cause the brakes to feel that way. So you should perform a thorough inspection to find the source of the issue.
Wrong wind back procedure
Not following the correct service procedure could cause the caliper piston to compress. Note that the rear calipers work differently from the front calipers. You can’t simply push the rear calipers back in. You have to twist and press them simultaneously.
Alternatively, you can use a wind-back tool to push back the rear caliper pistons easily. So you need to follow the proper instructions to compress them.
How to retract caliper piston with an integrated parking brake
Instead of a manual mechanism via a hand brake lever and floor pull, the electric application produces the clamping force by an actuator, which in this case of the integrated parking brake, is directly on the disk brake caliper.
The driver activates the parking brake via a switch, and the brake pads are electrically applied to the rear wheels. You will need a diagnostic tool to rewind the caliper piston with an electric parking brake.
When it’s time to replace your brake pads and rotors, you must retract the caliper pistons into the service mode position before removing the brake caliper assembly. There are two ways to do this:
- A diagnostic scan tool
- Through Uconnect or the cluster’s EVIC display for vehicles without touchscreen radios.
The method you choose may vary depending on the make and model of the vehicle, but here are the basic steps to retract the caliper piston with an integrated parking brake.
- Disconnect and isolate the negative battery cable. This prevents the parking brake from actuating with the caliper removed from the bracket. The parking brake motor will extend if this happens, damaging the caliper piston.
- Connect the car battery charger; otherwise, you can damage parts and cause further electronic issues.
- Connect the diagnostic tool or parking brake tool to your vehicle. Ensure the scanning tool communicates with the car and the battery voltage is stable.
- Now you can retract the parking brake pistons. You can either use a diagnostic tool scanner or a special tool for your electronic parking brake.
- Go to the brake app in the scanner and activate the retraction. You will hear the pistons retracting for about 2-3 seconds.
- After releasing the parking brake pistons, raise the car, then remove your wheel and the brake caliper.
- Use a pair of pliers, a flathead screwdriver, or a brake piston wind-back tool to push back the pistons. If they feel stuck, the piston might be rusty, or you did not successfully retract it with the diagnostic tool in the previous step.
- Also, if the parking brake motor is not released, the pistons won’t retract into the caliper.
- Once the pistons are back in, you can replace the brake pads. Remember to lubricate all moving parts and clean everything to ensure they don’t get stuck.
- Reinstall the brake caliper and tighten everything securely according to the manufacturer’s specifications.
- Reinstall the wheel and lower the car.
- After everything is in order, get into the car and pump the brake pedal several times until it feels hard. But do not push it to the bottom as it may damage the seals in the brake cylinder.
- When the brake pedal feels stiff, use the diagnostic or parking brake tool to move back the brake pistons. But in most cars, you will use the button to engage the parking brake. You should hear the parking brake motors sound until it is engaged, then release it.
- Finally, use the diagnostic tool to calibrate the pistons to ensure the parking brake functions properly. This allows the vehicle to learn how much it should engage and release. You will then hear the pistons repeatedly move back and forth until the calibration is complete.
- Now you can test the parking brake function and drive around to ensure the brake isn’t getting hot.
Conclusion
The rear brake pistons ensure your car comes to a stop successfully. Also, all other parts of the vehicle’s braking system must be in good condition. So before replacing the worn-out brake pads, you’ll have to compress the piston back into the caliper.
Ideally, you’d use a brake caliper rewind tool to do this, but if you don’t have one, you can always improvise with a screwdriver or pliers. We hope this article answers your questions about pushing a brake piston without a caliper piston tool.