Brake Caliper Rebuild
If you recall from my last post, the dust boots on the brake calipers had experience some heat damage. I opted to take the car to the dealership, since I had little experience with this kind of damage or repair.
I quickly discovered my local Porsche dealer is not track-friendly. They immediately recommended that I replace the calipers. The service manager tried to reason with the master tech, but he’s by the book and not willing to do anything but what Porsche NA recommends – not fix – but replace. Facing the prospect of a several thousand dollar repair bill, I opted to take the car home and began searching for caliper rebuilt kits. I found the caliper rebuild kit for the 991.1 at RacingBrake. At first, I was just looking for new boot covers. Though, as I read and researched, it turns out the stock caliper pistons from Porsche are aluminum and have a high, heat transfer factor. Stainless steel pistons were a better option. I also opted for a silicon dust boot that can handle 450 degrees, instead of the stock boots that are rated for 300 degrees. The guys at RacingBrake were helpful in ensuring I picked up the right kits to complete the job. I also picked up a set of titanium shim plates at Schnell Motorsports to further help.
With the parts on order, I began searching for the steps. While I didn’t find the exact process for the 991, I did find a perfectly good set of instructions for a Boxster by Road and Race on YouTube. I bought a set of tube clamps from my local AutoZone. One by one, I clamped the rubber brake line to the rotor. I placed an aluminum baking pan from the kitchen under the caliper and rotor to catch any brake fluid that might drip/spill. My wife was none the wiser and I did not return it to the kitchen afterwards. I disconnected the stainless steel brake line from the caliper. With the brake line clamped, I saw very little brake fluid leaking from the system. What little that spilled, fell into the pan.
First up, I need to remove the dust boots. They were stubborn, since they had melted and cracked. With a pick and hook set, I was able to pull the boots. In order to get to the inner seal, I needed to remove the pistons. Sometimes they can be pulled with little effort. I was having some difficulty. I attempted to use a flat blade screw driver to pry, but be careful not to damage the piston or caliper. When that didn’t work, I used my air compressor set at 50lbs pressure to eject the pistons by pumping air into the brake line inlet on the back of the caliper. With the piston out, I then used the pick tool to extract the inner seal within the piston cavities. I used fresh brake fluid to clean the caliper.
I then put the fresh, new inner seals into the piston cavity. I then coated the piston in some brake grease and inserted the new stainless piston into the caliper. Once all pistons were seated, I installed the new dust boots, being careful not to get any brake fluid on them. The silicon dust boot will chemically melt if brake fluid gets on the boot.
I then inserted the new pads, Pagid RS29s (yellows), along with the new titanium shims, and used the caliper spreader to open them up to be placed back onto the rotor. While I had everything apart, I decided to go ahead and replace the rotors with the Girodisc setup. Having fixed my braking technique, I was confident that I wouldn’t ruin these expensive beasts.
Then, everything gets put back together. Then next time I swap pads, I’ll be sure to post a video of this process. Remember, the caliper bolts are to be torqued to 63lbs. Don’t forget to flush the brake fluid. You’ve just emptied all the brake fluid from the calipers, so a full flush is required. You’ll want to follow the steps outlined in this rennlist forum post. The power bleeder is a fantastic tool to make this go very quickly. If you have any questions, hit me up via the contact form.