If you are the proud owner of a Type R (FK8 or FL5) and actively push its limits on the track, it’s highly likely that you’ll need to replace the dust boots or even the seals on your calipers. During my first track day, when I put my car through its paces, I realized that the heat generated in the brakes caused my dust boots to dry out and develop unsightly cracks. And this was only my first track day with the car.
Don’t sweat it if you fit the bill. I can personally vouch for the fact that having a set of dried-up and cracked dust boots on your car is not the end of the world. Frankly, I drove the car for another 2 years (10+ track days) without bothering to replace them. Yes, during that time, they did continue their decline, but after the first track day when they dried out and cracked due to the intense heat, there really wasn’t much more damage to be done. Sure, perhaps a few more tiny fragments chipped off the dust boot over those two years, but there was never any significant deterioration. That’s precisely why it took me two years to rebuild them finally.
Some might argue that with deteriorated dust boots, I was asking for trouble as they could potentially allow more dirt and debris to reach the piston and piston seal. Once dirt and debris start compromising the dust boots, it can lead to premature wear of the piston seal or even damage to the piston surface. And that, my friend, can result in hydraulic fluid leakage, loss of brake pedal pressure, or even the risk of catching fire. But rest assured, I sailed through those 2 years with confidence, unscathed by any catastrophic failures.
During those two years, every time I swapped out my brake pads, I’d take a peek at the dust boots and think, “Yep, they’re still good.” But after neglecting them for so long, it felt like I was practically begging for trouble. So, not wanting my luck to run out, I finally decided to give those calipers a much-needed overhaul.
Truth be told, I bet there are a lot of dried-out dust boots on cars with people driving around none the wiser. And honestly, you could probably go (insert arbitrarily large number) miles before ever running into an issue. But for people like us who track our cars and demand the utmost performance from them, a little rebuild now and then just to ensure some peace of mind is worth its weight in gold. I will now cite my favorite adage: “An ounce of prevention is worth a pound of cure.”
Now, let’s get on to what you all came here for… The actual rebuild procedure!
Due to my negligence in changing the dust boots for several years, I have made the proactive decision to fully disassemble and rebuild the caliper. This thorough process entails the installation of new dust boots and seals for each piston. It is highly recommended, especially for avid track enthusiasts, as it provides an additional layer of assurance and peace of mind.
I’m going to start with my car already up on jack stands and the front wheels off. If you are unsure of what it takes to get to this point, I might suggest you take your car to a professional to have them rebuild the calipers, as faulty installation can lead to total brake failure. But, if you are confident in getting to this point, the actual rebuild process isn’t hard, and it really only requires some patience.
As you can see below, this is what your car should look like at the start.
To ensure the proper disconnection of the brake line from the caliper without causing damage to the flare nut, it is highly recommended to utilize a flare nut wrench. By using this specialized tool, the risk of rounding off the brake line can be significantly reduced. The size needed for the FK8/FL5 caliper brake line is 10mm. Pro tip: use a quality brand flare nut wrench. Cheaper ones made from inferior metals can flex and still round off the flare nut. You know the old saying… Buy once, cry once!
You can see below where the brake hard line connects to the backside of the caliper.
Stop! Before you proceed any further, I highly recommend acquiring some silicone rubber plugs. I found great success with the 3/16th-inch plugs, which effectively seal off the brake line once it’s disconnected from the caliper. By doing so, you can rest assured that the brake fluid won’t continue to drip out while the line remains disconnected. Taking this proactive step helps to maintain control and prevent any potential complications.
If you fail to prevent the brake fluid from leaking out, not only will you encounter a major fluid spill on the ground, but you will also completely deplete the brake fluid reservoir. Allowing the reservoir to completely drain may lead to the introduction of air into the brake master cylinder, making it exceedingly difficult to effectively bleed your brakes without having to perform a bench bleeding procedure on the master cylinder.
The following image portrays the insertion of a 3/16th-inch plug into the brake line. Notably, it is important to mention that I left the plug in the brake line for several days, observing that the brake fluid did not compromise the integrity of the silicone material and no fluid leakage occurred. Additionally, it is essential to reiterate the necessity of completely re-bleeding the entire brake system after you complete the rebuild on the calipers. With the insertion of the plug, the goal is to prevent the fluid from fully draining out of the reservoir, thereby streamlining the brake bleed procedure.
With the line now removed, we can begin to remove the pads. Because I frequently change my pads, I made my own brake pin removal tool. I simply went to Harbor Freight, purchased a set of punches, found the one that fit best in the caliper (3/16th punch), and then drilled a small hole in the tip of it to help seat onto the point of the caliper pin. This allows for a more secure connection to the brake caliper pins when hammering them out.
I always opt for a plastic-coated dead blow hammer. It is the ideal choice to avoid any paint chipping if, by any chance, I accidentally hit the caliper while striking the punch during pin removal.
Now, with both pins and the anti-rattle spring removed.
Gently wiggle each pad back and forth to slightly compress the pistons back into the caliper, releasing the tension from each pad and allowing for easy removal. Once there is a little bit of wiggle, the pad will easily lift out. Go easy here, since the brake line is no longer connected to the caliper. As you compress the pistons back in, fluid will squirt out.
With both pads removed, you can unbolt the X2 19 mm bolts that secure the caliper to the knuckle.
This is what it should now look like.
Take the caliper and place it on a solid surface where you have plenty of room to work. It would be a good idea to lay a towel down first to ensure that you don’t scratch the red-painted caliper.
Below is a close-up of my cracked and dried-out dust boots.
Annnnnnd the other caliper.
Here is an alternative perspective. From this vantage point, one can also observe the desiccated and fissured state of the dust boots. The drying process has not only caused them to crack but also to undergo a slight contraction, thereby facilitating the infiltration of debris into the piston area.
Now it’s time to begin disassembling the caliper. Start by removing both bleeder screws.
The factory service manual calls to remove both (inboard and outboard) bleed screws, which I originally did. However, I wasn’t getting the desired air pressure it took to force the pistons out, so I hand-threaded one bleed screw back in and was able to get all four pistons extracted.
The factory service manual calls for a special tool, a brake caliper piston compressor. But a 2×4 works just as well.
Now, take compressed air and blow it into the brake line hole. By doing this, you will force the pistons out of the caliper. Caution! You must have something placed inside the caliper to stop the pistons from completely ejecting from the caliper. If you don’t use wood, a large/thick towel, or the factory service manual-suggested brake caliper piston compression tool, the pistons will eject from the caliper at a dangerous velocity and you’ll most likely end up damaging them.
Upon careful observation, it becomes evident that I had successfully detached one dust boot before expelling the pistons. Although this was done, due to the dry and cracked condition of the dust boots, which made their removal without complete deterioration quite challenging, I decided to proceed and forcefully expelled the pistons while leaving the other three dust boots intact. As depicted in the image below, this action resulted in the tearing of the remaining three dust boots. However, it ultimately facilitated the easier removal of the remaining rubber from the caliper with the pistons already extracted.
DO NOT use any sort of pliers or clamping tool to pull stubborn pistons all the way out. This will result in scarring/marring the piston, which will ultimately render them useless. If you have a stubborn piston or two, use your hands, fingers, or some sort of airtight material to cover the holes where the pistons have already been removed from. This will force the air to be applied only to the stubborn piston(s).
Here, you can see the four pistons that have been removed and the completely disintegrated dust boots.
The actual piston seals remain in the caliper. And, as you can see, mine don’t actually look that bad!
Next, you will need to delicately use a pick tool to remove the old seals. Be very careful here not to scratch the cylinder surface.
Here is what the seal looks like when removed from the caliper.
Here, you can observe the grooves engraved within the cylinder, specifically designed to accommodate the seals.
Inboard.
Outboard.
Below is the OEM seal and boot kit. You will need one kit per side (two in total). Also, take a look at the date when I originally ordered them! I had initially ordered them right after my first track weekend but then found out it was too tedious to try swapping out the dust boots without removing the caliper and ended up procrastinating for two years.
Once all pistons, old seals, and dust boots are removed from the caliper, make sure you thoroughly clean the caliper by spraying copious amounts of brake cleaner through all the bleed screw holes, the brake line hole, and all four piston holes. Make sure that while spraying brake cleaner into every orifice, you rotate the caliper around 360 degrees to ensure that all old brake fluid is drained out. Then, make sure to allow enough time for the brake cleaner to completely dry before reassembly.
Now, secure the dust boots to the piston. Gently work them onto the piston and ensure they are completely set into the groove on the piston.
Here is a close-up of what that looks like.
Next, it’s time to install the seals. You will need brake fluid to help lubricate the seals and ensure they don’t get damaged as you push the pistons back into the calipers.
I carefully poured a sufficient amount of brake fluid into the cap and delicately applied a thin layer of the fluid around the complete seal using my fingertips.
Use any means you choose to spread the brake fluid all around the new seal. Just ensure that you completely coat the entire seal.
Now, the seals can be placed in their resting grooves in the caliper. Again, ensure adequate lubrication by rubbing more brake fluid around them with your fingertips after installation.
See the screenshot below from the factory service manual, indicating where to apply brake fluid to the dust boots and seals.
Once everything has all been properly lubricated, the pistons can now carefully be pressed back in. Your fingers will provide adequate force to get the pistons back in.
- Do not press the piston diagonally, and do not force them.
- Be careful not to damage the piston boots when pressing in the pistons.
Once the pistons are back in, use some force to ensure the dust boot is properly seated into the caliper.
You should be able to feel when the dust boot is fully seated and bottomed out into the caliper. But because the caliper has some tapered surfaces, the seals may not look like they are fully seated when in fact they actually are. See the image below for what fully seated dust boots look like.
I just wanted to quickly demonstrate which tool you should use if you are only replacing the dust boots and don’t want to eject the pistons. Use a plastic interior tool to pry the old dust boot off. This will ensure you don’t damage the piston.
One could employ this technique should they desire a more meticulous approach for a thorough disassembly and reassembly. However, I have observed that employing a forceful burst of compressed air to expel the pistons and forcefully tearing apart the worn-out dust boots has yielded satisfactory results. This approach is preferred as it simplifies the removal of the dust boot from the caliper after piston removal.
Once all 4 pistons are back in the caliper, it’s time to bolt everything back on.
Start by hand-threading the bleeder screws back in and then snug them down. They only need to be torqued to 10 lb./ft., so don’t go crazy, especially since you’re going to be cracking them open when you go to bleed the calipers.
Then slide the caliper back over the rotor and secure it to the knuckle via two 19mm bolts. These are to be torqued to 103 lb/ft.
Lastly, thread the flare nut of the brake line into the backside of the caliper. The flare nut should only be torqued to 11 lb/ft.
Then, reinstall the pads, anti-rattle spring, and secure them all with the caliper pins. Use a plastic-coated hammer to tap the pins in from the backside of the caliper ensuring the pins are fully seated against the backside of the caliper.
Here is the finished product, all reassembled and ready for the bleeding process.
So, some of you sharp readers may have noticed that we began the post with OEM wheel studs, and now you’re seeing these MSI extended wheel studs. Pretty cool, right? Last week’s blog post happens to be about installing these wheel studs on my car. If you’re interested in learning about the extended wheel stud installation process, click the link below.
And, check out the pic above more closely. You’ll see that the brake air guide isn’t the one that comes stock on the FK8.
I have exciting news to share! After some experimentation and ingenuity, I have successfully found a way to make the air guides from the cutting-edge FL5 Type R perfectly fit our beloved FK8 Type R. This breakthrough is a testament to the power of determination and resourcefulness. You too can embrace this opportunity to enhance our vehicle even further by clicking the link below.
“Art is in the eye of the beholder, and everyone will have their own interpretation.”
The authentic masterpiece radiates with unwavering confidence, mirroring the essence of divine perfection.
Once both sides are completely put back together, it is time to completely bleed the entire brake system. Follow the instructions I snipped from the factory service manual below.
Make sure you bleed the outboard bleeder screw first.
Then, move to the inboard bleeder screw.
Once the front left and front right are bled, then move to the right rear, then the left rear (as instructed in the first picture).
Once both rears are done, it is imperative that you follow the instructions below about cycling the E brake on and off at least FIVE times.
Normally (because I have a slight case of obsessive-compulsive disorder), I tend to perform that entire sequence thrice just to guarantee that ALL the air has been expelled from my system. It is worth noting that since the front brake calipers are completely dry, they will absorb a significant amount of brake fluid as you purge the air from them. It is crucial to closely monitor the fluid level in the reservoir and ensure it does not drop too low during the bleeding process. Should it significantly deplete and introduce air into the brake master cylinder, it will likely be necessary to bench bleed the master cylinder before resuming the brake bleeding process individually at each caliper.
If you’re feeling a bit lazy, and only want to change your dust boots. You don’t necessarily have to remove the calipers from the knuckle just to change the dust boots. I happen to know a handful of people who have successfully replaced the dust boots while the caliper is still securely bolted to the knuckle. It can indeed be done. However, there are a few important steps to keep in mind. First, you’ll need to remove the brake pads, which will give you a bit more space to work with. Second, you’ll need to exercise an admirable level of patience and precision in completing the task. Due to the limited accessibility of the dust boots when the caliper is still attached, it can become quite tedious. Additionally, there is a slight risk of inadvertently damaging the piston or the new dust boot during the process. So approach this task with confidence and attention to detail.
Thank you to all the devoted enthusiasts who find my ramblings fascinating and consistently return to devour the latest articles. Your unending fascination fuels my passion for delivering fresh content. Please keep coming back for more! If you have any comments, questions, or simply want to say thank you, you can reach me via Instagram @Functiontheory, email Billy@Functiontheory.com, or simply comment on the post below, and I will reply back to you!