Changing a brake caliper is, in general, a pretty easy process, with the exception of bleeding the brakes. Depending on the kind of brake lines you have, the process of bleeding the brakes can be a little different.

So, when changing a caliper, is it always necessary to bleed all four of the brakes? If you have independent brake lines, as most modern cars do, it’s not usually required. However, if your car is older than 20 years, there’s a chance it might not have independent brake lines.

In this article, we’ll be going over everything you should know about bleeding your brakes, including how to do it, the different types of brake lines, and why it’s important to bleed your brakes in the first place.

What Are the Different Types of Brake Lines?

If your car is fairly modern, then it most likely comes with independent brake lines. As the name suggests, this means that every wheel gets its own brake line. 

If you’re not sure whether or not your car has independent brake lines, it’s pretty easy to find out. You just have to look for the ABS module in your engine bay and see how many brake lines are coming out of it. If you have independent brake lines, there will be four lines coming out of the ABS module, one for each wheel.

However, if you have a 3-channel ABS system, then you will only have three brake lines servicing four wheels. 3-channel systems usually have a separate brake line for each of the front wheels, but a shared brake line for both of the rear wheels.

If this is the case with your car, then you don’t need to bleed all four of your brakes as long as you’re just working on one of the front calipers, but you’ll need to bleed both of the rear brakes if you’re working on one of the rear calipers.

Why Bleed Your Brakes?

It’s always a good idea to bleed your brakes whenever you’re working on them. The purpose of bleeding brakes is to remove any air that might become trapped in the brake lines at any point.

As you may know, modern brake systems use hydraulic brake fluid to actuate the brakes. When you press down on the brake pedal, the hydraulic pressure in the brake lines forces the brake pads against the rotors, which slows the wheels down. However, there needs to be consistent hydraulic pressure for this to work.

If air bubbles get into the brake lines, this can severely mess with the hydraulic pressure and make the brakes much less effective. Some of the signs that you have air bubbles in your brake lines include increased stopping distances and a brake pedal that feels unusually spongy when you press it.

You should have your brakes bled any time you’re working on your brake system, but you should also bleed them every two to three years anyway, just to be safe. 

How to Bleed Your Brakes

Before we get into how to bleed your brakes, we’d suggest that you get a friend to help you out with this. It’s a lot easier to do this with a helping hand, as some aspects of the bleeding process will require you to be in two places at once otherwise.

With that being said, here’s how to go about correctly bleeding your brakes:

Step 1: Find the Right Brake Fluid

First, you need to make sure that you’re adding the right kind of brake fluid to your system. There are several types, and using the wrong type can potentially damage your brakes.

To make sure you’re adding the right type of fluid, check your owner’s manual; it should have all of that information on hand. 

Step 2: Prepare Your Vehicle

To bleed your brakes, your need to remove your car’s wheels. If you’re bleeding all four brakes then you’ll need to remove all four wheels, otherwise, you just have to remove the wheel from the brake you want to work on.

Once your car is jacked up, secure it in place with a jack stand. If you’re just bleeding one brake line, you should chock the wheel on the opposite corner from the one you’re working on.

Step 3: Loosen the Bleeding Screw

On the caliper, there will be a bleeding screw that you will need to open in order to let the brake fluid out. Loosen the bleeding screw, but don’t remove it from the caliper entirely.

If the screws are sticky, however, refrain from twisting them too hard, as you can end up snapping them off. Instead, give the screw a good spray with some penetrating oil, and allow it to sit for about half an hour before trying again.

Step 4: Top Up Your Master Cylinder

Ideally, the brake fluid master cylinder should be completely full with brake fluid before you start bleeding the brakes. If the fluid in the cylinder is anywhere below the “full” line, fill it up until it’s at the line.

Once you actually start bleeding the brakes, leave the cap in place on top of the master cylinder, but don’t screw it back on just yet. If you’re bleeding all four of your brakes, you should start with the brake that is farthest away from the master cylinder. 

Step 5: Fit the Bleeding Tubes

Get some clear tubing about 1/4 of an inch in diameter, and fit it over the end of the bleeder screw. Place the other end up the tube into a catch container (an empty soda can or water bottle is fine for this).

Make sure you place the catch container up higher than the bleeder screw, as this will prevent air from travelling back into the bleeder screw when you open it.

Step 6: Bleed the Brakes

Now, it’s time for the actual brake bleeding to begin. If you have a helper, this is where they’ll come in.

Have your helper sit in the car with the engine off and pump the brakes until they feel some resistance. Once they do, they should say something like “pressure” to let you know. Have them keep their foot on the brake in the meantime.

When your helper indicates that they’re feeling the pressure, open the bleeder screw. Brake fluid should immediately start flowing out, and the brake pedal should start sinking to the floor. When the brake pedal is almost touching the floor, your helper should let you know; this will be your cue to close the bleeder screw.

Check the master cylinder after doing this, and top it up again if the level of the brake fluid inside is too low. Now, repeat everything outlined in this step at least five more times until you can see that the fluid inside the bleeding tubes is free of air bubbles. 

Step 7: Check Your Work

Once you’ve finished bleeding the brakes you wanted to work on, it’s time to test your work. Have your helper push down all the way on the brake pedal and then quickly release it. If you see a big burst happen in the fluid, it means you’ll need to bleed the brakes again, but a small amount of movement means that everything is probably fine.

If your brakes are fully bled, all you need to do is tighten the bleeder screws and reinstall your wheels, and you should be good to go!