Crunching brake noise fixed!

My '02 996 Carrera had been making a rather odd crunching sound from the driver's side front brake when the brake pedal was pressed down all the way. I would typically hear the noise when coming to a full stop and holding the brakes fairly hard. Diagnosing the issue was more challenging than I thought, as the noise was loud and reverberated inside the wheel well. The brake rotors and pads were fairly new and not the cause of the noise. I also removed the fastener spring to eliminate it as the cause. I next replaced the brake line with upgraded to teflon/stainless to improve braking feel and also in hopes of addressing the issue. That didn't work either, so finally I decided to rebuild the caliper with new piston seals and dust boots and that finally addressed the noise! There is a similar thread on this noise from years ago on the 996 Turbo thread where you can hear a sound recording of the noise I was referring to: https://rennlist.com/forums/996-turb...ake-noise.html Rebuilding a brake caliper is not overly difficult or expensive and I've detailed the basic steps below. You'll need to order the proper kit for your application and ensure you're using brake caliper assembly lube if you want to do the job properly and as easy as possible. I ordered my kit from Automotive Brake Solutions as they had everything I needed including the lube which can be hard to find. They also have the most competitive prices vs ordering from Stoptech, Brembo or others and I received my parts the day after I ordered them (!). Here is the kit I ordered: https://autobrakesolutions.com/produ...44229744034110 Here is my process for removing the brake caliper: 1) Jack up car and remove wheel and turn steering wheel to have more access to the rear of the brake caliper 2) Use a screw driver or similar tool to carefully pry brake pads away from the caliper. When working on brakes, always remove the brake fluid reservoir top and remove brake fluid if you believe it may overflow during this job. 3) Remove hard brake line going into the back of the caliper, typically requires 10mm flare wrench (to avoid stripping fastener nut). The brake line will weep fluid, so be prepared with a bucket to catch the fluid initially. I used a leftover brake caliper bleeder valve rubber cover to plug it up. Remember, you're going to have to bleed this line later, so ensure you have the proper bleeding tools and brake fluid before you start this process. 4) Remove the hard brake line bracket connected to the wheel hub so there is no stress on the brake line (10mm bolt) 5) Unplug brake wear sensor line from connection on the hub and ensure the wire is not tied to any other wires. It's usually strapped to two other spots 6) Now the only thing connecting the brake caliper to the rotor are two large allen bolts, which I remove with a 10mm allen socket bit. How to remove pistons and seals from brake caliper: There are a few techniques to doing this, many which can be found on RL, but here's a short summary. If you've never done this before, be mindful to place your finders in the middle of the caliper where any of the pistons can shoot out and hurt you. Also, if you're going to be using air pressure, be extremely careful with how much pressure you use, where your fingers are placed and wear eye protection. 1) Find a piece of wood to place in the middle of the brake caliper which allows enough space for the pistons to mostly come out, which completely leaving the calipers 2) Use an air compressor and place the nozzle into the back of the brake caliper where you removed the brake line and carefully apply air pressure. In this first go, 20PSI will likely be enough to cause the smaller pistons to start protruding. For my brakes, I had to use 40PSI to have the larger pistons come out. Once they do come out its usually very violent and loud, so be prepared and ensure you're blocking their path so they can't fly out and get damaged. 3) If you're having trouble getting the pistons out, remove one of the two bleeder screws and relocate it to the hole behind the caliper and then introduce pressured air from one of the bleeder screws. 4) If you're still having trouble getting one or more pistons out, remove the pistons which are now mostly protruded, remove their dust caps and seals (seals are inside the brake caliper hole), carefully return the piston back in and hold it in using plastic clamps. This will allow some air to escape through them and allow to apply more air pressure to remove the stubborn pistons. This is when I used 40 PSI. 5) With the pistons removed, carefully remove the dust caps and seals in the bores. Be careful not to scratch, scrape, or damage the pistons or bores as they will lead to leaks later. 6) Install the new seals and note the two different sizes. For my Carrera, each side has a 36 and 40mm piston, seal and dust cap. Once the seal is installed, brake apply assembly lube to the seal and ensure it's pressed in all the way and is fly. 7) Install dust boot to the top of the piston and apply brake assembly lube around the piston and carefully insert it in the bore and press it in. Ensure it has been inserted straight. This may require some pressure to get the piston past the seal, but after the first one you'll feel much more confident about the process. 8) Once the piston is pressed in all the way, apply pressure around the dust boot to ensure it's pressed in all the way and sitting flush. Apply this process to all pistons, tighten any bleeder valves you've loosen and install back on the car. Bleed brake line, ensure the pads and pad sensor cable and properly installed, double check bolts, etc. Pictures... Green 10mm bolt should be remove to release tension on brake line connecting to caliper The '02 996 Carrera has four pistons, two 40mm and two 36mm. The brakes for the S, Turbo and GT models will have different size pistons. The original dust caps who no signs of wear or leakage. Dust caps and pistons removed. New seals, cleaned pistons and new dust caps installed.

What do you use to clean residue from the Pistons?