Replacing your brake pads is generally a pretty easy procedure unless your caliper pistons have become seized. In this case, the pistons may be protruding from the caliper and getting in the way of where the brake pad is supposed to be.

Fortunately, it’s possible to compress the piston back into its original position if you have a piston compression tool. Even if you don’t, there are still some alternative methods you can use to fix this problem.

Today, we’ll be going over some of the reasons why your brake caliper piston might not be compressing to begin with, and explain how you can compress your pistons whether or not you have the specific tool for the job.

Why Is My Brake Caliper Piston Not Compressing?

Before you immediately start trying to compress your piston, it’s a good idea to determine why exactly the piston is unable to compress in the first place. There could be a more serious issue at play that you will need to address before working on the piston.

Here are a few of the reasons why your brake piston may be unable to compress:

Worn Piston Boot

The piston boot is a rubber seal that goes around the opening where the piston sits in the caliper. The purpose of the piston boot is to keep out moisture, dirt, and other things that can corrode the piston and cause it to stick. However, if the boot gets worn out, it can cause your piston to start corroding pretty quickly.

If your piston boots look cracked or torn, or feel hard and brittle to the touch, this is a sign that the boots are worn out and should be replaced.

Lack of Driving

Corrosion can also happen if you let a vehicle sit for a long time without driving it. Contrary to what you might think, letting a vehicle sit for a long time can actually cause some of its components to start breaking down more quickly.

Unless you have no other choice, you should never let your car sit for longer than a month or so without driving it. When you do decide to take your car out for a spin, try and drive it for at least 10 minutes before parking it again.

Wrong Wind-Back Procedure

It’s important to mention that the procedure for compressing a brake piston is different depending on whether you’re working on the front or rear brakes. The front brake pistons are fairly easy to work on because you can just push them back in, but the rear brake pistons are a little more challenging; you have to simultaneously push in on the piston while turning it.

For this reason, it’s a really good idea to actually have purpose-built tools for this job. It is still possible to compress your rear brake pistons without the proper tools, but you’ll have a much harder time doing this for sure.

How to Compress Your Brake Pistons

Now that we’ve talked about some of the common issues that can cause your brake pistons to seize up, let’s talk about how to address the issue of a stuck brake piston itself. We’ll be going over a few different ways to do this, depending on whether you have the right tools or not.

Preparing Your Car

First, before you actually begin the process of compressing your brake pistons, you need to prepare your car. Start by making sure your car is on a level surface, and then jack up your car by the wheel you want to work on. Secure the car with a jack stand, and chock the wheel on the opposite corner of the car from the one you’re working on.

Remove the wheel from the car so that you have access to the brake lines, and detach the brake line from the caliper. You should use something to prevent the brake fluid from leaving the line, like a small clamp or a hose plug.

Next, undo the caliper bolts, and remove the caliper from the brake rotor. At this point, you should be all ready to start compressing your brake pistons, so let’s talk about some of the ways you can do that now.

Method 1: Piston Compression Tool

If you have a brake piston compression tool on hand, this is definitely what you should use for the job. There’s the possibility that you’ll accidentally damage your brakes if you use an unsuitable tool to compress your brake pistons, but using an actual piston compression tool pretty much removes this risk entirely.

Brake piston compression tools use a plunger to force the piston back into the caliper. To use this tool, you just need to place it on the caliper so that the plunger is in contact with the piston. Then, just pump the tool repeatedly until the piston is fully compressed inside the caliper again.

Method 2: Tongue-and-Groove Pliers

If you don’t have a proper piston compression tool, you can use a pair of tongue-and-groove pliers to perform this repair. To avoid damaging the piston, however, you’ll need to place something in between the pliers and the piston. A small piece of wood or rubber will probably be fine for this purpose.

Place the pliers on the caliper so that the piston gets pushed inward when you squeeze the pliers and squeeze them until the piston is fully compressed. Start by squeezing gently, and then gradually increase the pressure until you’re done.

Method 3: C-Clamp

A c-clamp is another tool you can use to compress a brake piston if you don’t have an actual compression tool on hand. This procedure is basically the same as using tongue-and-groove pliers.

To start with, you should place a piece of wood or rubber in between the c-clamp and the piston to prevent the piston from being damaged. Then, place the c-clamp over the caliper so that it pushes the piston in when you start to tighten it. All you need to do now is turn the c-clamp’s screw until the piston is fully compressed again.